JPWO2016114177A1 - Method for producing metal oxide particles - Google Patents

Abstract

According to the method for producing metal oxide particles of the present invention, a preheated metal chloride-containing gas is joined with a preheated first gas not containing metal chloride at a first joining point to form a first joining gas, Including the step of joining the preheated second gas not containing metal chloride to the first combined gas at a second combined point separated downstream from the first combined point to form a second combined gas, Both the substance-containing gas and the first gas do not contain oxygen or water vapor, the second gas contains at least oxygen, and the preheating temperature of the first gas is set to be equal to or higher than the preheating temperature of the metal chloride-containing gas. The preheated metal chloride-containing gas is joined and heated, and the preheating temperature of the second gas is merged with the first merged gas at a temperature equal to or higher than the temperature of the first merged gas, and downstream from the second merged point. And heating the first combined gas.

Description

The present invention relates to a method for producing metal oxide particles, and more particularly to a method for producing metal oxide particles for producing metal oxide particles for a long time without clogging a raw material gas flow path.
The present invention claims priority based on Japanese Patent Application No. 2015-005149 filed in Japan on January 14, 2015, the contents of which are incorporated herein by reference.

In recent years, titanium oxide particles have attracted attention in the field of photocatalysts. For example, Patent Documents 1 and 2 and Non-Patent Documents 1 to 3 have titanium oxide particles (hereinafter referred to as “decahedron titanium oxide particles”) having a decahedral box shape and mainly composed of anatase crystals. Is disclosed.
Patent Documents 1 and 2 and Non-Patent Documents 1 and 3 describe that decahedral titanium oxide particles have a large surface area per unit mass, high crystallinity, and few internal defects, and therefore have high activity as a photocatalyst. Has been. Non-Patent Document 2 describes that decahedral titanium oxide particles have a high ratio of (001) surfaces with high reactivity and are promising as photocatalysts.

As a method for producing decahedral titanium oxide particles, for example, there is a method utilizing hydrothermal reaction using hydrofluoric acid described in Non-Patent Document 2. However, since hydrofluoric acid has a strong acidity and is difficult to handle, the production method of Non-Patent Document 2 using this is not suitable for industrial use.
In the method for producing decahedral titanium oxide particles described in Patent Documents 1 and 2 and Non-Patent Documents 1 and 3, titanium tetrachloride (TiCl ₄ ) vapor and oxygen (O ₂ ) gas are introduced into the reaction tube. In this method, these gases are heated from the outside of the reaction tube to produce titanium oxide particles TiO ₂ by the reaction shown in the following reaction formula (1).
TiCl ₄ + O ₂ → TiO ₂ + 2Cl ₂ (1)

By using the said manufacturing method, the powder product containing a titanium oxide particle can be obtained in the downstream of a reaction tube. This powdery product contains a large amount of decahedral titanium oxide particles.
The above-described production methods described in Patent Documents 1 and 2 and Non-Patent Documents 1 and 3 use titanium tetrachloride as a raw material when the raw material gas is rapidly heated to a temperature at which the thermal oxidation reaction of titanium tetrachloride proceeds. And oxygen gas is heated from the outside of the reaction tube. Therefore, when the flow rate of the raw material gas containing titanium tetrachloride and oxidizing gas is large, all the titanium tetrachloride in the raw material gas is consumed by the thermal oxidation reaction from the heat source outside the reaction tube to the raw material gas in the reaction tube. As a result, the necessary heat conduction is not ensured, the reaction is not completed, and unreacted titanium tetrachloride remains downstream from the reaction zone, resulting in a decrease in the yield of the resulting powder product. Occurs.

On the other hand, in the production method described in Patent Document 3, the flow rate of the raw material gas is large by joining titanium tetrachloride as a raw material in two stages with the preheated first gas and second gas and heating them. Even in this case, titanium oxide particles having a high photocatalytic activity can be produced in a high yield.
However, in the manufacturing method described in Patent Document 3, since at least one of the preheated titanium tetrachloride-containing gas and the preheated first gas contains oxygen, the titanium tetrachloride-containing gas is introduced. Tip, inner surface, outer surface of the first hollow inner cylinder made of quartz glass, tip of the second hollow inner cylinder made of quartz glass to which the first gas is introduced, and titanium oxide adhering matter, film-like product, deposit on the inner surface However, when the titanium oxide particles are produced for a long period of time, they are gradually accumulated and eventually the source gas flow path is closed, and the first hollow inner cylinder and the second hollow inner cylinder Causes a problem of damage.
The above-mentioned tip, inner surface, outer surface of the first hollow inner cylinder, the tip of the second hollow inner cylinder made of quartz glass for introducing the first gas, the sticking matter, the film-like product, and the deposit accumulated on the inner surface Even if production is interrupted and these are scraped off with a jig or the like before the source gas flow path is closed, the glass is often broken because it is firmly fixed to the glass.

Japanese Patent No. 4145923 JP 2006-52099 A JP 2011-184235 A

Daisuke Kusano, Yoshihiro Terada, Ryu Abe, Satoshi Otani, The 98th Catalysis Conference (September 2006), Discussed Conference A Proceedings, page 234 Hua Gui Yang et al. , Nature, Vol. 453, p. 638-p. 641 Amano F.M. et al. , Chem. Mater. , 21, 602-1603 (2009)

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of the metal oxide particle which manufactures a metal oxide particle with high photocatalytic activity for a long time.

  In the reaction tube, the metal chloride-containing gas containing the preheated metal chloride is combined with the first gas preheated at a temperature equal to or higher than the preheat temperature of the metal chloride-containing gas to heat the metal chloride-containing gas. The gas is further heated by combining the second gas preheated at a temperature higher than the temperature of the combined gas with the combined gas heated to a temperature higher than the preheating temperature of the metal chloride-containing gas. In the method, the inventors found that metal oxide particles having high photocatalytic activity can be produced for a long time by not containing oxygen and water vapor in both the metal chloride-containing gas and the first gas, and completed the following invention.

In order to achieve the above object, the present invention employs the following configuration. That is,
(1) In the reaction tube, the preheated metal chloride-containing gas is joined with the preheated first gas not containing the metal chloride at the first joining point to form the first joining gas, and the first joining gas Metal oxide particles including a step of joining the preheated second gas not containing the metal chloride at a second joining point farther downstream than the first joining point to form a second joining gas Both the metal chloride-containing gas and the first gas do not contain oxygen or water vapor, the second gas contains at least oxygen, and the preheating temperature of the first gas is increased. The first gas is joined at the first joining point at a temperature equal to or higher than the preheating temperature of the metal chloride-containing gas, so that the first joining point to the second joining point (referred to as a first zone). ), The pre-heated metal chloride-containing gas Are further heated, and the preheating temperature of the second gas is merged with the first merged gas as a temperature equal to or higher than the temperature of the first merged gas, so that the first merge is performed downstream from the second merge point. A method for producing metal oxide particles, wherein the gas is further heated.
(2) The method for producing metal oxide particles according to claim 1, wherein the metal chloride is titanium tetrachloride, and the metal oxide particles are titanium oxide particles.
(3) The method for producing metal oxide particles according to (2), wherein the titanium oxide particles are decahedral titanium oxide particles.
(4) The method for producing metal oxide particles according to any one of (1) to (3) above, wherein a preheating temperature of the metal chloride-containing gas is 600 ° C. or higher and 1000 ° C. or lower.
(5) The method for producing metal oxide particles according to any one of (1) to (4) above, wherein the temperature of the first combined gas is 800 ° C. or higher and 1050 ° C. or lower.
(6) The method for producing metal oxide particles according to any one of (1) to (5) above, wherein the temperature of the second combined gas is 800 ° C. or higher and 1100 ° C. or lower.
(7) The method for producing metal oxide particles according to any one of (1) to (6) above, wherein the preheating temperature of the first gas is 800 ° C. or higher and 1050 ° C. or lower.
(8) The method for producing metal oxide particles according to any one of (1) to (7), wherein a preheating temperature of the second gas is 900 ° C. or higher and 1100 ° C. or lower.
(9) The method for producing metal oxide particles according to any one of (1) to (8) above, wherein the metal chloride-containing gas contains nitrogen gas.
(10) The metal oxidation as described in any one of (1) to (9) above, wherein the first gas includes one or more gases selected from the group consisting of nitrogen gas and argon. Method for producing product particles.
(11) Any one of (1) to (10) above, wherein the second gas includes one or more gases selected from the group consisting of nitrogen gas, argon and water vapor together with oxygen gas. The manufacturing method of the metal oxide particle as described in a term.
(12) The metal oxidation as described in any one of (2) to (11) above, wherein the concentration of the titanium tetrachloride contained in the first combined gas is 0.1 to 20% by volume. Method for producing product particles.
(13) The metal oxide as described in any one of (1) to (12) above, wherein a time in which the first combined gas stays in the first zone is 2 to 100 milliseconds. Particle production method.
(14) The method for producing metal oxide particles according to any one of (1) to (13), wherein the Reynolds number of the second combined gas is 10 to 10,000.

  According to said structure, the manufacturing method of the metal oxide particle which manufactures a metal oxide particle with high photocatalytic activity for a long time can be provided.

  In the method for producing metal oxide particles according to the present invention, a preheated first gas containing no metal chloride is joined to a preheated metal chloride-containing gas in a reaction tube at a first joining point. And a second preheated gas that does not contain the metal chloride is joined to the first joining gas at a second joining point that is further downstream than the first joining point. A method for producing metal oxide particles, wherein both the metal chloride-containing gas and the first gas do not contain oxygen and water vapor, and the preheating temperature of the first gas is set to the metal chloride. The metal chloride-containing gas preheated between the first joining point and the second joining point is obtained by joining the first gas at the first joining point as a temperature equal to or higher than the preheating temperature of the contained gas. Further heating, the preheating temperature of the second gas A metal oxide having a high photocatalytic activity is obtained by further heating the first combined gas downstream from the second combined point by combining the first combined gas with a temperature equal to or higher than the temperature of the first combined gas. The particles can be produced for a long time.

  In the method for producing metal oxide particles of the present invention, it is preferable that titanium tetrachloride is used as the metal chloride, and the metal oxide particles to be produced are titanium oxide particles, and also in this case, the metal chloride Both the contained gas and the first gas do not contain oxygen and water vapor, and the first gas is brought into the first merge with the preheating temperature of the first gas being equal to or higher than the preheating temperature of the metal chloride-containing gas. By merging at the point, the metal chloride-containing gas preheated between the first merging point and the second merging point is further heated, and the preheating temperature of the second gas is changed to the first gas merging point. Titanium oxide particles having high photocatalytic activity by further heating the first combined gas downstream from the second combined point by combining with the first combined gas at a temperature equal to or higher than the temperature , It can be produced for a long time.

  The apparatus for producing metal oxide particles according to the present invention includes a reaction tube and a preheating unit for preheating each of the metal chloride-containing gas, the first gas, and the second gas, and the reaction tube has a hollow outer surface. A cylinder, a second hollow inner cylinder inserted from the upstream side of the hollow outer cylinder to the middle of the hollow outer cylinder, and inserted from the upstream side of the second hollow inner cylinder to the middle of the second hollow inner cylinder. A first conduit that introduces the first gas preheated upstream thereof, and the hollow outer cylinder is preheated upstream thereof. A second conduit for introducing the second gas, the preheated metal chloride-containing gas is introduced from the upstream side of the first hollow inner cylinder, and the introduced metal chloride-containing gas is the first gas The first gas preheated at the downstream end of the hollow inner cylinder merges, and the merged gas is below the second hollow inner cylinder. By being able to further merges with the second gas that has been preheated at the end, a high metal oxide particles having photocatalytic activity, can be produced for a long time.

It is a schematic diagram which shows an example of the manufacturing apparatus of the metal oxide particle of this invention. It is a scanning electron micrograph of the metal oxide particle (titanium oxide particle) of Example 1, and is a photograph of 100 k times.

  Hereinafter, a metal oxide particle manufacturing method and manufacturing apparatus according to an embodiment to which the present invention is applied will be described in detail with reference to the drawings. Note that the drawings used in the following description are shown schematically and briefly for easy understanding of the features, and the dimensional ratios of the respective components are not the same as the actual ones.

<Production equipment for metal oxide particles>
FIG. 1 is a schematic view showing an example of a production apparatus used in the method for producing metal oxide particles according to an embodiment of the present invention.
As shown in FIG. 1, the manufacturing apparatus 101 used in the manufacturing method of the metal oxide particle which is embodiment of this invention is the hollow outer cylinder 1, and the hollow outer cylinder from the upstream (upstream part) 1a of the hollow outer cylinder 1. The second hollow inner cylinder 5 inserted to the middle of 1 and the first hollow inner cylinder 4 inserted from the upstream side 5a of the second hollow inner cylinder 5 to the middle of the second hollow inner cylinder 5 While having the reaction tube 11, the heat insulating material 2 is arrange | positioned so that a part of reaction tube 11 may be heat-retained outside the reaction tube 11, and is comprised roughly.

<Reaction tube>
As shown in FIG. 1, the reaction tube 11 includes a hollow outer cylinder 1, a first hollow inner cylinder 4, and a second hollow inner cylinder 5. The reaction tube 11 is configured by a cylindrical tube made of, for example, quartz.
The second hollow inner cylinder 5 is inserted partway from the upstream side 1 a of the hollow outer cylinder 1, and the downstream end 5 b is arranged so as to be near the center in the longitudinal direction of the hollow outer cylinder 1. The first hollow inner cylinder 4 is inserted partway from the upstream side 5 a of the second hollow inner cylinder 5, and the downstream end 4 b is disposed so as to be near the center in the longitudinal direction of the second hollow inner cylinder 5. ing.

<Metal chloride-containing gas>
The metal chloride-containing gas G1 preheated in the preheating region (preheating portion) X is poured into the first hollow inner cylinder opening 24 on the upstream side 4a of the first hollow inner cylinder 4.
Although not shown in the figure, a vaporizer for evaporating a metal chloride such as titanium tetrachloride (TiCl ₄ ) is installed on the upstream side of the preheating region X, and a liquid is installed on the upstream side of the vaporizer. An introduction pipe for introducing the metal chloride into the vaporizer and an introduction pipe for supplying a gas containing nitrogen are connected to the vaporizer through valves. The vaporizer has a function of evaporating a liquid metal chloride into a metal chloride vapor by setting the temperature to 165 ° C., for example. Thereby, it is set as the structure which can supply the metal chloride containing gas G1 which consists of mixed gas containing a metal chloride vapor | steam and nitrogen to the preheating area | region X. FIG.

  The metal chloride-containing gas G1 is a gas containing steam such as titanium tetrachloride. Specifically, a mixed gas of a vapor such as titanium tetrachloride and nitrogen, or a mixed gas of a vapor such as titanium tetrachloride and an inert gas containing nitrogen can be used as the metal chloride-containing gas G1.

<First gas>
The first gas G2 preheated in the preheating region (preheating portion) Y flows into the ring-shaped opening 25 between the downstream side 4b of the first hollow inner cylinder 4 and the upstream side 5a of the second hollow inner cylinder 5. It is.

  The first gas G2 is a gas containing no metal chloride such as titanium tetrachloride, oxygen, and water vapor. Specifically, the first gas G2 is an inert gas such as nitrogen or argon, and these may be used alone or in combination. Therefore, a gas composed of only nitrogen, a gas composed of only argon, a mixed gas of nitrogen and an inert gas such as argon, or the like can be used.

<Second gas>
The second gas G3 preheated in the preheating region (preheating portion) Z is poured into the ring-shaped opening 26 between the downstream side 5b of the second hollow inner cylinder 5 and the upstream side 1a of the hollow outer cylinder 1.

The second gas G3 is a gas that does not contain a metal chloride such as titanium tetrachloride. Specifically, the second gas G3 contains at least oxygen (O ₂ ). The second gas G3 may contain oxygen, an inert gas such as nitrogen or argon, water vapor and ozone (O ₃ ), or a mixture thereof. Accordingly, the second gas G3 is in a state of only oxygen, a state of a mixed gas of inert gas such as nitrogen or argon and oxygen, a state of a mixed gas of water vapor and oxygen, or a mixture of inert gas, water vapor and oxygen. The state of gas can be taken. Note that air may be used as a mixed gas of an inert gas and oxygen.

  It is preferable that the first hollow inner cylinder 4 and the second hollow inner cylinder 5 have a coaxial structure. Thereby, the metal chloride-containing gas G1 can be collected on the central axis side, and the diffusion of titanium tetrachloride vapor to the inner wall surface of the second hollow inner cylinder 5 is suppressed, and the inner wall surface of the second hollow inner cylinder 5 is suppressed. Generation of a film-like product (by-product) that adheres to the substrate can be suppressed.

  Moreover, it is preferable that the second hollow inner cylinder 5 and the hollow outer cylinder 1 have a coaxial structure. Thereby, diffusion of titanium tetrachloride vapor to the inner wall surface of the hollow outer cylinder 1 is suppressed, and generation of a film-like product (byproduct) that adheres to the inner wall surface of the first hollow outer cylinder 1 can be suppressed. it can.

<Insulation material>
As shown in FIG. 1, a heat insulating material 2 is disposed outside the reaction tube 11 to keep the gas in the reaction tube warm. A normal ceramic fiber is used as the heat insulating agent.

<First meeting point>
The metal chloride-containing gas G1 and the first gas G2 merge at the downstream end 4b of the first hollow inner cylinder 4. The merge point between the two is called the first merge point.

<First combined gas>
The gas merged at the first merge point is referred to as a first merge gas.

<Second meeting point>
The first merged gas and the second gas G3 merge at the downstream end 5b of the second hollow inner cylinder 5. The merge point between the two is referred to as a second merge point.

<Second combined gas>
The gas merged at the second merge point is called the second merged gas.

<First Zone>
A region through which the first merged gas passes from the first merge point (the downstream end 4b of the first hollow inner cylinder 4) to the second merge point (the downstream end 5b of the second hollow inner cylinder 5) passes through the first zone. That's it.

<Second reaction zone>
A region through which the second merged gas passes from the second merge point (downstream end 5b of the second hollow inner cylinder 5) to the downstream end of the heat insulating material 2 is referred to as a second reaction zone. In the second reaction zone, titanium tetrachloride vapor in the second combined gas is consumed by the oxidation reaction.

<Preheating area>
In the metal oxide particle manufacturing apparatus 101 according to the embodiment of the present invention, three preheating regions X, Y, and Z are provided.

  The preheating regions X, Y, and Z are configured by arranging an electric heater (not shown) or the like outside each gas flow path. In the preheating regions X, Y, and Z, the metal chloride-containing gas G1, the first gas G2, and the second gas G3 are set to predetermined preheating temperatures, respectively.

The preheating temperature of the preheating region X (preheating temperature of the metal chloride-containing gas G1) is preferably set to a temperature range of 600 ° C. to 1000 ° C., more preferably 650 ° C. to 950 ° C., More preferably, the temperature range is 800 ° C. or higher and 950 ° C. or lower.
By setting the range of the preheating temperature in the preheating region X to a range of less than 600 ° C., the photocatalytic activity of the finally obtained powder product is lowered. Further, by setting the preheating temperature range of the preheating region X to a range of 1000 ° C. or higher, the rutile ratio increases and the decahedron ratio decreases. As a result, the photocatalytic activity of the finally obtained powder product decreases.
By setting the preheating temperature range of the preheating region X to 600 ° C. or more and 1000 ° C. or less, the ratio of decahedral titanium oxide particles in the finally obtained powder product is increased, and as a result, a decahedral having high photocatalytic activity. Titanium oxide particles are obtained.

  The preheating temperature of the preheating region Y (preheating temperature of the first gas G2) is set to a range of 800 ° C. or more and 1050 ° C. or less as the temperature higher than the preheating temperature of the preheating region X (preheating temperature of the metal chloride-containing gas G1). Is more preferable, and a temperature range of 850 ° C. or higher and 1050 ° C. or lower is more preferable.

  By combining the preheating temperature of the first gas G2 as a temperature equal to or higher than the preheating temperature of the metal chloride-containing gas G1, and further heating the metal chloride-containing gas G1 preheated in the preheating region X in the first zone, The ratio of decahedral titanium oxide particles in the obtained powder product is high, and the photocatalytic activity is increased. Conversely, if the preheating temperature of the first gas G2 is lower than the preheating temperature of the metal chloride-containing gas G1, the ratio of decahedral titanium oxide particles in the finally obtained powder product is low, and the photocatalytic activity decreases. To do.

  When the preheating temperature of the preheating region Y is less than 800 ° C., the ratio of decahedral titanium oxide particles in the obtained powder product is low, and the photocatalytic activity is low. When the preheating temperature in the preheating region Y is higher than 1050 ° C., the rutile ratio of the obtained powder product becomes high, the ratio of decahedral titanium oxide particles is low, and the photocatalytic activity decreases. By setting the preheating temperature of the first gas G2 to be equal to or higher than the preheating temperature of the metal chloride-containing gas G1, the rutile ratio in the finally obtained powder product is lowered by setting the temperature range to 800 ° C. or higher and 1050 ° C. or lower. The ratio of decahedral titanium oxide particles is increased, and as a result, decahedral titanium oxide particles having high photocatalytic activity are obtained.

  The preheating temperature of the preheating zone Z (preheating temperature of the second gas G3) is set to a temperature range of 900 ° C. or higher and 1100 ° C. or lower as the temperature higher than the preheating temperature of the preheating zone Y (preheating temperature of the first gas G2). Preferably, the temperature range is 950 ° C. or higher and 1050 ° C. or lower. By setting the preheating temperature of the second gas G3 to a temperature equal to or higher than the first combined gas temperature, combining the two at the second combined point, and further heating the first combined gas in the second reaction zone, the decahedral ratio is high. Highly photocatalytically active particles can be obtained.

  When the preheating temperature in the preheating zone Z is lower than 900 ° C., the temperature of the second combined gas, that is, the temperature of the second reaction zone is lowered, and the reaction is not completed in the second reaction zone, and the resulting powder is produced. In some cases, the yield of the product decreases. When the preheating temperature of the preheating region Z is higher than 1100 ° C., the rutile ratio in the finally obtained powder product is high, the ratio of decahedral titanium oxide particles is low, and as a result, the photocatalytic activity is lowered. .

<First combined gas temperature>
In the reaction tube 11, a first zone B is provided between the first merging point (the downstream end 4 b of the first hollow inner cylinder 4) and the second merging point (the downstream end 5 b of the second hollow inner cylinder 5). It has been. In the first zone B, the preheated metal chloride-containing gas G1 and the preheated first gas G2 merge to form a first merged gas, and the first merged gas flows until the second gas G3 merges. It is an area.
The first combined gas temperature is preferably in the temperature range of 800 ° C. or higher and 1050 ° C. or lower, more preferably 850 ° C. or higher and 1000 ° C. or lower, and still more preferably 900 ° C. or higher and 1000 ° C. or lower. By setting the first combined gas temperature in the temperature range of 800 ° C. or higher and 1050 ° C. or lower, the ratio of decahedral titanium oxide particles in the finally obtained powder product is increased, and high photocatalytic activity is obtained.

  When the first combined gas temperature is less than 800 ° C., the ratio of decahedral titanium oxide particles in the finally obtained powder product is lowered, and the photocatalytic activity is lowered. When the second combined gas temperature is higher than 1050 ° C., the rutile ratio of the finally obtained powder product is increased, and the photocatalytic activity is decreased.

The calculation method of the first combined gas temperature T ₁ [° C.] will be described by taking as an example a case where titanium tetrachloride and nitrogen are used as the metal chloride-containing gas G1, nitrogen is used as the first gas G2, and oxygen is used as the second gas G3. .
T ₁ = Q ₁ / C ₁ ,
Q ₁ = Q _{R, T} + Q _{R, N} + Q _{1G, N} ,
Q _{R, T} = GR _{, T} × Cp _T × T _R ,
QR _{, N} = GR _{, N} × Cp _N × T _R ,
Q _{1G, N} = G _{1G, N} × Cp _N × T _1G ,
C ₁ = GR _{, T} × Cp _T + GR _{, N} × Cp _N + G _{1G, N} × Cp _N.
Here, Q ₁ is the total amount [kcal] of the amount of heat brought into the first junction by the metal chloride-containing gas G1 and the first gas G2, C ₁ is the heat capacity [kcal / ° C.] of the first junction gas, and Q _{R , T} is the amount of heat carried into the first confluence by titanium tetrachloride in the metal chloride-containing gas G1, and QR _{and N} are the amounts of heat carried into the first confluence by nitrogen in the metal chloride-containing gas G1. [Kcal], Q _{1G, N} is the amount of heat brought into the first confluence by nitrogen in the first gas G2 [kcal], GR _{, T} are mass flow rates of titanium tetrachloride in the metal chloride-containing gas G1 [kg / h], Cp _T is the specific heat [kcal / (kg · ℃) of titanium tetrachloride], _{T R} is the preheat temperature of the metal chloride-containing gas _{G1, G R, N} is nitrogen of the metal chloride-containing gas G1 Mass flow rate [kg / h], Cp _N is the ratio of nitrogen Heat [kcal / (kg · ° C.)], G _{1G, N} is the mass flow rate of nitrogen in the first gas G2 [kg / h], Cp _N is the specific heat of nitrogen [kcal / (kg · ° C.)], T _1G Is the preheating temperature [° C.] of the first gas G2. The calculation was performed with Cp _T = 0.6 [kcal / (kg · ° C.)] and Cp _N = 1.2 [kcal / (kg · ° C.)].

<Second combined gas temperature>
In the reaction tube 11, a second reaction zone A is provided between the downstream end 5 b of the second hollow inner cylinder 5 and the downstream end of the heat insulating material 2. The second reaction zone A is a region in which the first combined gas and the preheated second gas G3 are combined to form a second combined gas, and the second combined gas flows. This is a region where the heat insulating material 2 is wound outside, and the gas in the reaction tube 11 is kept warm in the second reaction zone A by winding the heat insulating material. The second combined gas temperature is preferably in a temperature range of 800 ° C. or higher and 1100 ° C. or lower, more preferably in a temperature range of 800 ° C. or higher and 1050 ° C. or lower, and a temperature range of 850 ° C. or higher and 1050 ° C. or lower. Is more preferable. By setting the second combined gas temperature to a temperature range of 800 ° C. or higher and 1100 ° C. or lower, the ratio of decahedral titanium oxide particles in the finally obtained powder product is increased, and high photocatalytic activity is obtained.

  When the first combined gas temperature is less than 800 ° C., the ratio of decahedral titanium oxide particles in the finally obtained powder product is lowered, and the photocatalytic activity is lowered. When the temperature of the second combined gas is higher than 1100 ° C., the rutile ratio of the finally obtained powder product is increased, and the photocatalytic activity is decreased.

Regarding the calculation method of the second combined gas temperature T ₂ [° C.], titanium tetrachloride and nitrogen are used as the metal chloride-containing gas G1, nitrogen is used as the first gas G2, and oxygen is used as the second gas G3. An example will be described.
T ₂ = Q ₂ / C ₂ ,
Q ₂ = Q _{1, T} + Q _{1, N} + Q _{2G, O} ,
_{Q 1, T = G 1,} T × Cp T × T 1,
_{Q 1, N = G 1,} N × Cp N × T 1,
_{Q 2G, O = G 2G,} O × Cp O × T 2G,
C ₂ = G _{1, T} × Cp _T + G _{1, N} × Cp _N + G _{2G, O} × Cp _O.
Here, _{Q 2} is the total amount of bringing heat to the second junction of the first combined gas and a second gas G3 [kcal], _{C 2} is the heat capacity of the second combined gas _{[kcal / ℃], Q 1} , T Is the amount of heat brought into the second joining point by the titanium tetrachloride in the first joining gas [kcal], Q1 _{, N} is the amount of heat brought into the second joining point by the nitrogen in the first joining gas [kcal], _{Q2G , O} is the amount of heat brought into the second confluence by oxygen in the second gas G3 [kcal], G1 _{, T} are mass flow rates of titanium tetrachloride in the first confluence gas [kg / h], G1 _{, N} Is the mass flow rate [kg / h] of nitrogen in the first combined gas, G _{2G, O} is the mass flow rate of oxygen in the second gas G3 [kg / h], and T _2G is the preheating temperature [° C. of the second gas G3. ]. Cp _T = 0.60 [kcal / (kg · ° C.)], Cp 2 _O = 1.1 [kcal / (kg · ° C.)], Cp _N = 1.2 [kcal / (kg · ° C.)] went.

<Product recovery unit>
A product recovery unit 3 that recovers a product such as metal oxide particles is connected to the downstream side 1 b of the hollow outer cylinder 1 via a discharge pipe 6. The product recovery unit 3 includes a bag filter or the like and can recover the generated metal oxide particles.
An exhaust pump 3a and a pressure adjusting valve 3b are connected to the downstream side of the product recovery unit 3. Usually, as the product accumulates in the product recovery unit 3 and the filter is clogged, the pressure inside the reaction tube 11 increases. By sucking with the exhaust pump 3a, this pressure increase can be suppressed, and an oxidation reaction to a metal oxide can be performed near normal pressure. At this time, it is preferable to adjust the suction force of the exhaust pump 3a by adjusting the pressure adjusting valve 3b. Thereby, metal oxide particles can be generated more efficiently.

When titanium tetrachloride is used as the metal chloride, the metal oxide particles recovered by the product recovery unit 3 are decahedral titanium oxide particles or other titanium oxide particles. The decahedral titanium oxide particles mean titanium oxide particles having a decahedral box shape as defined in Patent Document 1.
Moreover, titanium oxide particles other than decahedral titanium oxide particles mean those not defined as the above-mentioned decahedral titanium oxide particles among the titanium oxide particles obtained by the production method of the present embodiment.

<Method for producing metal oxide particles>
Next, the manufacturing method of the metal oxide particle which is embodiment of this invention is demonstrated using the manufacturing apparatus 101 of the metal oxide particle shown in FIG.
The method for producing metal oxide particles according to an embodiment of the present invention includes a metal chloride-containing gas G1 containing a metal chloride, a first gas G2 not containing the metal chloride, and a metal chloride-free gas G1. A step of preheating the two gases G3 (hereinafter referred to as a preheating step), the metal chloride-containing gas G1 and the first gas G2 are joined to form a first joined gas, and the first joined gas is formed. Gas and the second gas G3 are merged to form a second merged gas, and the metal chloride is reacted in the second reaction zone.
Hereinafter, the case where titanium tetrachloride is used as the metal chloride and titanium oxide is generated as the metal oxide particles will be described.

<Preheating process>
The metal chloride-containing gas G1 preheated at a constant preheating temperature in the preheating region X is poured from the upstream side 4a of the first hollow inner cylinder 4.

  A mixed gas (first gas G2) composed of nitrogen preheated at a constant preheating temperature in the preheating region Y is poured into the ring-shaped opening 25 between the first hollow inner cylinder and the second hollow inner cylinder.

  A mixed gas (second gas G3) composed of oxygen, nitrogen, and water vapor preheated at a constant preheating temperature in the preheating zone Z is poured into the ring-shaped opening 26 between the second hollow inner cylinder and the hollow outer cylinder 1.

  The metal chloride-containing gas G1 ejected from the downstream end 4b of the first hollow inner cylinder 4 merges with the first gas G2 ejected from the ring-shaped opening 25 at the downstream end 4b of the first hollow inner cylinder 4. To form a first combined gas. That is, the downstream end 4b of the first hollow inner cylinder 4 is a merging point (first merging point).

<Reaction process>
In the second reaction zone A, the oxidation reaction of the reaction formula (1) proceeds at the second combined gas temperature, and titanium tetrachloride is changed to titanium oxide. When the second combined gas passes through the second reaction zone A, the metal oxide in the combined gas is rapidly cooled to generate a powder product composed of titanium oxide particles.

The range of the time during which the second combined gas stays in the second reaction zone A is preferably less than 300 milliseconds, more preferably less than 200 milliseconds, and even more preferably less than 150 milliseconds. When the distance of the heat insulating material 2 in the axial direction of the reaction tube is increased, and the time during which the second combined gas stays in the second reaction zone A that is a heat retaining region is 300 milliseconds or more, aggregation between particles occurs, and the specific surface area is increased. And the photocatalytic activity of the resulting powder product is reduced.
The second combined gas showing a method for calculating the time t ₂ staying in the second reaction zone. t ₂ = L ₂ / Ve _{2, T 2,} Ve _{2, T 2} = Vo _{2, T 2} / S _2R , Vo _{2, T 2} = Vo _{2, 0 ° C.} × (273.15 + T ₂ ) /273.15, Vo _{2, 0 ℃ = Vo 1,0 ℃ + Vo 2G} , 0 ℃, Vo 1,0 ℃ = Vo R, 0 ℃ + Vo 1G, is calculated using the formula _{0 ° C..}
Here, L ₂ is the length of the second reaction zone in the axial direction of the reaction tube [m], Ve _{2 and T} 2 are second combined gas temperature converted values [m / s] of the linear velocity of the second combined gas, Vo _{2. , T2} is the second combined gas temperature converted value [m ³ / s] of the second combined gas flow rate, S _2R is the cross-sectional area [m ² ] of the second reaction zone, Vo _{2 and 0 ° C.} are the second combined gas. The flow rate converted to 0 ° C., T ₂ is the second combined gas temperature, Vo ₁ , _{0 ° C.} is the first combined gas flow rate 0 ° C. converted value, Vo _{2G, 0 ° C.} is the second gas G 3 flow rate 0 ° C. The converted value, Vo _{R, 0 ° C.} is the 0 ° C. converted value of the metal chloride containing gas G1 flow rate, and Vo _{1G, 0 ° C.} is the 0 ° C. converted value of the first gas G2 flow rate.

  In order to suppress aggregation between particles on the downstream side of the heat insulating material 2, it is desirable to effectively cool the gas in the reaction tube. The methods include natural heat dissipation from the reaction tube wall surface, blowing cooling air from the outside of the reaction tube, and introducing cooling air into the reaction tube.

[Titanium tetrachloride concentration]
In the region 27 from the downstream end 4b of the first hollow inner cylinder 4 to the downstream end 4b of the second hollow inner cylinder 5, the metal chloride-containing gas G1 and the first gas G2 are merged at the first junction point. The concentration of titanium tetrachloride in the first combined gas is preferably 0.1 to 20% by volume, more preferably 0.5 to 10% by volume, and 0.5 to 5% by volume. Is more preferable. By setting the concentration of titanium tetrachloride in the first combined gas within the above range, decahedral titanium oxide particles having high photocatalytic activity can be obtained.

  Moreover, in the said area | region 27, the primary particle diameter of the titanium oxide particle which comprises the powder product finally obtained becomes small, so that the titanium tetrachloride density | concentration in the 1st combined gas which flows through a 1st zone is low, and a specific surface area. Will increase. By setting the titanium tetrachloride concentration in the first combined gas flowing in the first zone within the above range, a powder product having high photocatalytic activity can be obtained.

[Residence time]
The time that the first combined gas stays in the first zone (hereinafter referred to as “residence time”) is preferably in the range of 2 to 100 milliseconds, and preferably in the range of 2 to 75 milliseconds. More preferably, it is still more preferably in the range of 20 to 50 milliseconds.

By installing the second joining point away from the downstream side of the first joining point, the first zone is installed, and the first joining gas stays in the first zone.
At this time, a trace amount of the second gas (second combustion support gas) flows backward. Therefore, when the residence time exceeds 100 milliseconds, a titanium oxide fixed substance, a film-like product, and a deposit are generated on the inner surface of the second hollow inner cylinder (especially the edge of the downstream end 5b) in the first zone. It becomes easy, the yield of the powder product finally obtained falls, a flow path is obstruct | occluded, and quartz glass is damaged. In addition, the rutile ratio increases and the photocatalytic activity decreases.
On the other hand, when the residence time is less than 2 milliseconds, it is easy to generate a fixed amount of titanium oxide around the tip and the periphery of the first hollow inner quartz tube, and finally the channel is blocked, and the quartz glass Will be damaged. Although the rutile ratio is lowered, the photocatalytic activity of the finally obtained titanium oxide particles is lowered.

By setting the time in which the first combined gas stays in the first zone to be in the range of 2 to 100 milliseconds, the titanium oxide adhering matter, the on-film product, and the adhering matter to the first and second hollow inner quartz tubes Can be produced for a long time with a high yield of 95% or more.
Moreover, the rutile ratio of the finally obtained titanium oxide particles is low, the ratio of decahedral titanium oxide particles in the powder product is increased, and the photocatalytic activity is increased.

The first combined gas shows a method for calculating the time t ₁ staying in the first zone. t ₁ = L ₁ / Ve _{1, T 1} , Ve _{1, T 1} = Vo _{1, T 1} / S _1G , Vo _{1, T 1} = Vo _{1, 0 ° C.} × (273.15 + T ₁ ) /273.15, Vo _{1, 0} Calculated by the equation: _{° C} = Vo _{R, 0 ° C.} + Vo _{1G, 0 ° C.}
Here, L ₁ is the length of the first zone in the axial direction of the reaction tube [m], Ve _{1, T1} is the first combined gas temperature converted value [m / s] of the linear velocity of the first combined gas, Vo _{1, T1} is the first combined gas temperature conversion value [m ³ / s] of the first combined gas flow rate, S _1G is the cross-sectional area [m ² ] of the first zone, Vo ₁ , _{0 ° C.} is the first combined gas flow rate 0 ° C conversion value, T ₁ is the first combined gas temperature, Vo _{R, 0 ° C} is the metal chloride-containing gas G1 flow rate 0 ° C conversion value, Vo _{1G, 0 ° C} is the first gas G2 flow rate 0 ° C It is a converted value.

[Reynolds number]
The Reynolds number of the second combined gas is preferably in the range of 10 to 10,000, more preferably in the range of 1000 to 4000, and still more preferably in the range of 2100 to 3000.
When the Reynolds number exceeds 10,000, the turbulent state of the combined gas becomes remarkable, and the effect of the oxidizing gas that suppresses the diffusion of titanium tetrachloride vapor from the vicinity of the central axis of the reaction tube 11 to the inner wall surface side is lost. In other words, the amount of the film-like product fixed to the inner wall surface of the reaction tube 11 increases. When the Reynolds number of the second combined gas is less than 10 and the laminar flow has a minute flow rate condition, or a remarkable turbulent flow condition exceeding 10,000, the ratio of decahedral particles in the powder product decreases, The photocatalytic activity is also reduced. By setting the Reynolds number of the second combined gas in the range of 10 to 10,000, the ratio of decahedral particles in the powder product is increased, and the photocatalytic activity is increased.

The Reynolds number Re is calculated by the equation Re = D × u × ρ / μ. Here, D is the inner diameter (m) of the hollow outer cylinder 1, u is the linear velocity (m / s), ρ is the density (kg / m ³ ), μ is the viscosity [kg / (mx s)].
In the present embodiment, 126 (mm) is used as the value of the inner diameter D of the hollow outer cylinder 1. As the value of u, the linear velocity (converted value of the second combined gas temperature) of the combined gas (Cl ₂ + O ₂ ) after the reaction in the second reaction zone is used. As the value of ρ, the density of the combined gas (Cl ₂ + O ₂ ) after the reaction (second combined gas temperature converted value) is used. Further, as the value of μ, the viscosity of the combined gas after the reaction (second combined gas temperature converted value) is used.

[Linear velocity u of merged gas]
As the value of the linear velocity u of the combined gas (Cl ₂ + O ₂ + N ₂ ) after the reaction in the second reaction zone, the linear velocity u of the second combined gas (TiCl ₄ + O ₂ + N ₂ ) (converted value of the second combined gas temperature). ) Can be used.
When all of the TiCl ₄ contained in the metal chloride-containing gas G1 is consumed by the reaction of the reaction formula (1) described above, twice (flow) amount of Cl ₂ is generated as compared with TiCl _4. At the same time, O ₂ is consumed by the amount of TiCl ₄ and the O ₂ flow rate decreases. However, since the generated TiO ₂ is a particle and not a gas, the flow rate of the entire gas flowing before and after this reaction does not change.

[Merge gas density ρ]
In order to calculate the value of the density ρ of the combined gas (Cl ₂ + O ₂ + N ₂ ) after reaction in the second reaction zone, the flow rate of the combined gas flowing per unit time (that is, the flow rate of the second combined gas) ) Is used.
First, let X _2T (m ³ / h) be a flow rate obtained by converting the flow rate of the combined gas after the reaction in the second reaction zone with the second combined gas temperature. The mass flow rate Y _{0 ° C. and 1 atm} (kg / h) of the combined gas is obtained using the flow rate in the standard state (0 ° C., 1 atm) of the flow rate X _2T (m ³ / h) of the combined gas after the reaction. At this time, the density of the combined gas after reaction in the second reaction zone is ρ = Y _{0 ° C., 1 atm} (kg) / X _2T (m ³ ).

In calculating the viscosity μ of the combined gas (Cl ₂ + O ₂ + N ₂ ) after the reaction in the second reaction zone, a calculation formula of μ = exp {a + b × ln (t + 273)} is used. In the above calculation formula, t is a temperature (° C.), and here is the second combined gas temperature. Further, a, b are constants determined by the type of gas used, the Cl ₂ is a = 0.015, a b = 0.864, for _{O 2} is a = 1.289, b = 0.711 N ₂ has values of a = 1.388 and b = 0.668. These values of a and b are values obtained by solving simultaneous equations of a and b from the already known combinations of t and μ.

The viscosity μ of the combined gas (Cl ₂ + O ₂ + N ₂ ) after the reaction is averaged by the following formula to determine the viscosity μ (converted to the second combined gas temperature) of the combined gas after the reaction.
Viscosity μ of the combined gas after reaction (second converted gas temperature converted value) = {(second combined gas temperature converted value of Cl ₂ flow rate) × (Cl ₂ viscosity converted to second combined gas temperature) + (O ₂ Second combined gas temperature converted value of flow rate) × (O ₂ viscosity converted to second combined gas temperature) + (Second combined gas temperature converted value of N ₂ flow rate) × (N ₂ converted to second combined gas temperature) Viscosity)} / {Flow rate of combined gas (Cl ₂ + O ₂ + N ₂ ) after reaction}

  As described above, the titanium oxide particles have been described as an example of the metal oxide particles. However, the present invention is not limited to this. For example, the metal oxide particles may be silicon oxide particles, tin oxide particles, or the like. In producing these metal oxide particles, a metal chloride-containing gas containing silicon tetrachloride vapor and tin tetrachloride vapor is used.

  When titanium oxide particles are produced as metal oxide particles, a mixed gas composed of titanium tetrachloride vapor and nitrogen is used as the metal chloride-containing gas, nitrogen gas is used as the first gas, and second gas G3 is used. Most preferably, oxygen gas is used. By using this combination, particles having high photocatalytic activity can be produced for a long time.

  According to the method for producing metal oxide particles according to the embodiment of the present invention, metal oxide particles having high photocatalytic activity can be produced for a long time. In particular, when titanium tetrachloride is used as the metal chloride and titanium oxide particles are produced as the metal oxide particles, the effect becomes remarkable.

  Since the method for producing metal oxide particles according to the embodiment of the present invention is a configuration in which the titanium oxide particles are decahedral titanium oxide particles, metal oxide particles having high photocatalytic activity can be produced for a long time.

  Since the method for producing metal oxide particles according to the embodiment of the present invention is configured such that the preheating temperature of the metal chloride-containing gas G1 is 600 ° C. or higher and 1000 ° C. or lower, metal oxide particles having high photocatalytic activity are produced for a long time. can do.

  In the method for producing metal oxide particles according to the embodiment of the present invention, since the temperature of the first combined gas is 800 ° C. or higher and 1050 ° C. or lower, metal oxide particles having high photocatalytic activity can be produced for a long time. it can.

  Since the method for producing metal oxide particles according to the embodiment of the present invention is configured such that the temperature of the second combined gas is 800 ° C. or higher and 1100 ° C. or lower, metal oxide particles having high photocatalytic activity can be produced for a long time. it can.

  Since the method for producing metal oxide particles according to the embodiment of the present invention is configured such that the preheating temperature of the first gas G2 is 800 ° C. or higher and 1050 ° C. or lower, metal oxide particles having high photocatalytic activity are produced for a long time. Can do.

  Since the method for producing metal oxide particles according to the embodiment of the present invention is configured such that the preheating temperature of the second gas G3 is 800 ° C. or higher and 1100 ° C. or lower, metal oxide particles having high photocatalytic activity are produced for a long time. Can do.

  The method for producing metal oxide particles according to an embodiment of the present invention is characterized in that the metal chloride-containing gas G1 contains nitrogen gas, and therefore, metal oxide particles having high photocatalytic activity are produced for a long time. be able to.

  In the method for producing metal oxide particles according to the embodiment of the present invention, since the first gas G2 includes one or more kinds of gases selected from the group consisting of nitrogen gas and argon, metal oxidation having high photocatalytic activity is performed. Product particles can be produced for a long time.

  In the method for producing metal oxide particles according to the embodiment of the present invention, since the second gas G3 includes one or more gases selected from the group consisting of oxygen gas, nitrogen gas, argon, and water vapor, a high photocatalyst Metal oxide particles having activity can be produced for a long time.

  Since the manufacturing method of the metal oxide particle which is embodiment of this invention is the structure which makes the density | concentration of the said titanium tetrachloride contained in 1st combined gas 0.1-20 volume%, the metal oxide which has high photocatalytic activity The particles can be produced for a long time.

  Since the method for producing metal oxide particles according to an embodiment of the present invention is configured such that the time during which the first combined gas stays in the first zone is 2 to 100 milliseconds, metal oxide particles having high photocatalytic activity are obtained. Can be manufactured for a long time.

  Since the method for producing metal oxide particles according to the embodiment of the present invention has a configuration in which the Reynolds number of the second combined gas is 10 to 10,000, metal oxide particles having high photocatalytic activity can be produced for a long time.

  The apparatus for producing metal oxide particles according to an embodiment of the present invention includes a reaction tube 11 and preheating sections X, Y, and Z that preheat the metal chloride-containing gas G1, the first gas, and the second gas, respectively. The reaction tube 11 includes a hollow outer cylinder 1, a second hollow inner cylinder 5 inserted from the upstream side 1a of the hollow outer cylinder 1 to the middle of the hollow outer cylinder 1, and the second hollow The first hollow inner cylinder 4 is inserted from the upstream side 5a of the inner cylinder 5 to the middle of the second hollow inner cylinder 5, and the second hollow inner cylinder 5 is preheated to the upstream side 5a. The hollow outer cylinder 1 is provided with a second conduit 16 for introducing the second gas preheated on the upstream side 1a thereof, and contains the preheated metal chloride. The gas G1 is introduced from the upstream side 4a of the first hollow inner cylinder 4, and the introduced metal chloride-containing gas G1 is the front The first gas preheated at the downstream end 4 b of the first hollow inner cylinder 4 merges, and the merged gas is further combined with the second gas preheated at the downstream end 5 b of the second hollow inner cylinder 5. Since it can be merged, metal oxide particles having high photocatalytic activity can be produced for a long time.

  Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited only to these examples. The present invention can be implemented with appropriate modifications within a range not changing the gist thereof.

Example 1
<Device preparation>
First, a quartz tube having an inner diameter of 126.0 mm is used as the hollow outer cylinder 1, and a quartz tube having an outer diameter of 27.0 mm, an inner diameter of 21.0 mm, and a thickness of 3.0 mm is used as the first hollow inner cylinder 4. 2 As the hollow inner cylinder 5, a quartz tube having an outer diameter of 61.0 mm, an inner diameter of 55.0 mm, and a thickness of 3.0 mm is used, and the hollow outer cylinder 1, the first hollow inner cylinder 4, and the second hollow inner cylinder 5 are The reaction tube 11 was produced by arranging it so as to be coaxial.

Next, a heat insulating material (ceramic fiber) 2 was wound around a part of the reaction tube 11 by 50 cm to set a second reaction zone A. On the downstream side of the heat insulating material 2, the temperature of the gas in the reaction tube 11 decreases due to heat radiation to the outside of the reaction tube 11. For this reason, the length of the 2nd reaction zone A was set by setting the length of a heat insulating material.
Next, the second hollow inner cylinder 5 was arranged so that the downstream end 5b of the second hollow inner cylinder 5 was positioned at the upstream end of the second reaction zone A. The second gas G3 preheated by the electric heater in the preheating region Z is introduced to the upstream side 1a of the hollow outer cylinder 1 upstream of the downstream end 5b of the second hollow inner cylinder 5.
Next, the 1st hollow inner cylinder 4 was arrange | positioned so that the downstream end 4b of the 1st hollow inner cylinder 4 may become a position upstream from the downstream end 5b of a 2nd hollow inner cylinder. The first gas G2 preheated by the electric heater in the preheating region Y is introduced to the upstream side 5a of the second hollow inner cylinder 5 upstream of the downstream end 4b of the first hollow inner cylinder 4. . The metal chloride-containing gas G1 preheated by the electric heater in the preheating region X is introduced into the upstream side 4a of the first hollow inner cylinder 4. The length of the first zone B was 14.0 cm. The length of the second reaction zone A was 50.0 cm.
The metal oxide particle manufacturing apparatus 101 shown in FIG. 1 was prepared as described above.

<Manufacturing process>
Next, the first gas G2 made of nitrogen (N ₂ ) gas is passed through the preheating region Y kept at 1010 ° C. by an electric heater to reach 1010 ° C., and then introduced from the upstream side 5a of the second hollow inner cylinder 5 did. The flow rate of the first gas G2 was set to 6.5 Nm ³ / h.
Next, the second gas G3 made of oxygen (O ₂ ) gas was passed through the preheating region Z kept at 1030 ° C. by an electric heater to reach 1030 ° C., and then introduced from the upstream side 1a of the hollow outer cylinder 1. The flow rate of the second gas G3 was 32 Nm ³ / h.
Next, a metal chloride-containing gas G1 composed of titanium tetrachloride (TiCl ₄ ) and nitrogen (N ₂ ) gas is passed through a preheating region X kept at 880 ° C. by an electric heater to reach 880 ° C., and then the first It was introduced from the upstream side 4 a of the hollow inner cylinder 4. The flow rate of the metal chloride-containing gas G1 was 1.3 Nm ³ / h.
The total flow rate (raw material gas flow rate) of the metal chloride-containing gas G1, the first gas G2, and the second gas G3 was 39.8 Nm ³ / h.

The residence time of the first combined gas in the first zone B was set to 32 milliseconds. The residence time of the second combined gas in the second reaction zone A was 118 milliseconds. The concentration of titanium tetrachloride in the first combined gas in the first zone B was 3.8% by volume (vol%). The first combined gas temperature was 979 ° C. The second combined gas temperature was 1020 ° C. The Reynolds number of the second combined gas in the second reaction zone A was 2800.
This Reynolds number is a value when it is assumed that the second combined gas is 1020 ° C. downstream of the downstream end 5 b of the second hollow inner cylinder 5. The residence time in the first zone is a value when it is assumed that the first combined gas is 979 ° C. downstream of the downstream end 4 b of the first hollow inner cylinder 4. The residence time in the second reaction zone assumes that the second combined gas is 1020 ° C. downstream from the downstream end 5 b of the second hollow inner cylinder 5, and the second combined gas is in the second hollow inner cylinder 5. This is a value obtained by calculating the residence time from the downstream end 5b to the downstream end of the heat insulating material 2.
Finally, metal oxide particles (Example 1) made of a powder product were recovered in the product recovery unit 3.

<Characteristic evaluation>
The characteristics of the metal oxide particles (Example 1) were evaluated as follows.
First, the yield of the powder product with respect to the raw material was 97%. The obtained powder product was titanium oxide particles.
“Yield of the powder product” refers to the mass of the titanium oxide product when all of the titanium tetrachloride used is converted to the titanium oxide product by the reaction of reaction formula (1) described above. , The proportion of mass of the powder product actually produced, ie titanium oxide particles.

Next, by observing with a scanning electron microscope, it was found that the proportion of decahedral titanium oxide in the powder product was 70%.
The ratio of decahedral titanium oxide particles (hereinafter referred to as “decahedron ratio”) is determined by observing titanium oxide particles (arbitrarily sampled powder product) with a scanning electron microscope in five or more fields of view. The ratio of decahedral titanium oxide particles contained in the titanium particles is calculated.
FIG. 2 is a scanning electron micrograph obtained by enlarging the metal oxide particles (titanium oxide particles) of Example 1 by 100 k times.
Moreover, it turned out that the specific surface area (BET) of the obtained particle | grains is 14 m < ² > / g.

  Next, it was found by X-ray diffraction measurement that the rutile ratio was 4%. This numerical value of the rutile ratio is a result obtained by estimating the ratio (%) of titanium oxide particles having a rutile crystal structure from the peak intensity obtained by X-ray diffraction measurement.

Next, the photocatalytic activity of the produced titanium oxide was evaluated using a gas chromatography method.
First, 10 mg of titanium oxide powder was placed in a petri dish having an inner diameter of 27 mm, dispersed by adding water, and then dried at 110 ° C.
Next, this petri dish was placed in a 500 ml chamber, the interior was replaced with synthetic air, and then xenon light source with 500 ppm acetaldehyde equivalent and 5.8 μl water (corresponding to 50% relative humidity at 25 ° C.). The amount of carbon dioxide (CO ₂ ) generated per hour was quantified by gas chromatography by irradiation with 0.2 mW / cm ² of light. As a result, the amount of carbon dioxide (CO ₂ ) generated as photocatalytic activity was 120 ppm / h.

(Examples 2 to 4)
The flow rate of the first gas G2, the concentration of titanium tetrachloride in the first combined gas, the residence time of the first combined gas in the first zone B, the residence time of the second combined gas in the second reaction zone A, the first combined gas temperature The second combined gas temperature and the metals of Examples 2 to 4 are the same as Example 1 except that the Reynolds number of the second combined gas in the second reaction zone A is changed as shown in Tables 1 and 2. Oxide particles were produced.

(Examples 5-7)
Titanium tetrachloride supply amount, titanium tetrachloride concentration in the first combined gas, residence time of the first combined gas in the first zone B, residence time of the second combined gas in the second reaction zone A, first combined gas temperature, Except for changing the second combined gas temperature and the Reynolds number of the second combined gas in the second reaction zone A as shown in Tables 1 and 2, the metal oxidation of Examples 5 to 7 was performed in the same manner as in Example 1. Product particles were produced.

(Example 8)
Preheating temperature of the first gas G2, residence time of the first joined gas in the first zone B, residence time of the second joined gas in the second reaction zone A, first joined gas temperature, second joined gas temperature, second reaction Example 8 metal oxide particles of Example 8 were produced in the same manner as in Example 1 except that the Reynolds number of the second combined gas in Zone A was changed as shown in Tables 1 and 2.

Example 9
The preheating temperature of the first gas G2, the preheating temperature of the second gas G3, the residence time of the first combined gas in the first zone B, the residence time of the second combined gas in the second reaction zone A, the first combined gas temperature, the first 2 except that the combined gas temperature and the Reynolds number of the second combined gas in the second reaction zone A are changed as shown in Tables 1 and 2, and the metal oxide particles of Example 9 were used in the same manner as in Example 1. Manufactured.

(Example 10)
Tables 1 and 2 show the preheating temperature of the second gas G3, the residence time of the second combined gas in the second reaction zone A, the second combined gas temperature, and the Reynolds number of the second combined gas in the second reaction zone A. The metal oxide particles of Example 10 were produced in the same manner as in Example 1 except that the above changes were made.

(Example 11)
Except for changing the preheating temperature of the metal chloride-containing gas G1, the first combined gas temperature, the second combined gas temperature, and the Reynolds number of the second combined gas in the second reaction zone A as shown in Tables 1 and 2. In the same manner as in Example 1, metal oxide particles of Example 11 were produced.

Example 12
The preheating temperature of the metal chloride-containing gas G1, the residence time of the first combined gas in the first zone B, the residence time of the second combined gas in the second reaction zone A, the first combined gas temperature, the second combined gas temperature, The metal oxide particles of Example 12 were produced in the same manner as in Example 1 except that the Reynolds number of the second combined gas in the two reaction zones A was changed as shown in Tables 1 and 2.

(Comparative Example 1)
The manufacturing apparatus of Comparative Example 1 has the same configuration as the manufacturing apparatus 101 of Example 1. Comparison was made in the same manner as in Example 1 except that the type of the first gas G2, the first combined gas temperature, and the Reynolds number of the second combined gas in the second reaction zone A were changed as shown in Tables 1 and 2. The metal oxide particles of Example 1 were produced.

(Comparative Example 2)
The manufacturing apparatus of Comparative Example 2 also has the same configuration as the manufacturing apparatus 101 of Example 1. Supply amount of titanium tetrachloride, type of first gas G2, concentration of titanium tetrachloride in the first combined gas, residence time of the first combined gas in the first zone B, residence time of the second combined gas in the second reaction zone A The first combined gas temperature, the second combined gas temperature, and the Reynolds number of the second combined gas in the second reaction zone A are compared in the same manner as in Example 1 except that they are changed as shown in Tables 1 and 2. The metal oxide particles of Example 2 were produced.

(Comparative Example 3)
The manufacturing apparatus of Comparative Example 3 also has the same configuration as the manufacturing apparatus 101 of Example 1. Type of first gas G2, residence time of first combined gas in first zone B, residence time of second combined gas in second reaction zone A, first combined gas temperature, second combined gas temperature, second reaction zone Metal oxide particles of Comparative Example 3 were produced in the same manner as in Example 1 except that the Reynolds number of the second combined gas at A was changed as shown in Tables 1 and 2.

(Comparative Example 4)
The manufacturing apparatus of Comparative Example 4 has the same configuration as the manufacturing apparatus 101 of Example 1. The flow rate of the first gas G2, the concentration of titanium tetrachloride in the first combined gas, the residence time of the first combined gas in the first zone B, the residence time of the second combined gas in the second reaction zone A, the first combined gas temperature The metal oxide of Comparative Example 4 was the same as Example 1 except that the second combined gas temperature and the Reynolds number of the second combined gas in the second reaction zone A were changed as shown in Tables 1 and 2. Particles were produced.

(Comparative Example 5)
For comparison of properties, commercially available titanium oxide particles for photocatalyst were purchased. The titanium oxide particles (Comparative Example 5) were particles synthesized by a flame method, and as a result of observation using an electron microscope, the particle shape was indefinite and the primary particle diameter was 20 to 60 nm. Further, from the results of X-ray diffraction measurement, it was found that the particles were a mixture of anatase and rutile.

Moreover, in Table 3, the yield of the powder product of Examples 1-12 and Comparative Examples 1-5, the decahedral ratio in a powder product, a photocatalytic activity, a specific surface area (BET measurement value, m < ² > / g), The rutile ratio is summarized.

In Comparative Examples 1 to 3 in which oxygen flows into the first combustion-supporting gas, although the titanium oxide deposit on the first and second hollow inner cylindrical quartz tubes is hardly generated at the initial stage of production, the production is continued. Over time, the titanium oxide deposit gradually accumulated, the flow path was blocked within the total production time of 5 to 20 hours, and the quartz glass was broken. For this reason, it turned out that production for a long time cannot be performed.
Comparative Example 3 was a production method according to the description in Patent Document 3 (Japanese Patent Laid-Open No. 2011-184235), and the photocatalytic activity and the yield of the powder product were high.
In Comparative Examples 1 and 2, the temperature of the first combustion-supporting gas was higher than that of the production method disclosed in JP2011-184235A, and thus the rutile ratio was high and the photocatalytic activity was low.
In Comparative Example 4, since the first combustion support gas does not flow at all, part of the oxygen of the second combustion support gas easily flows back into the second hollow inner cylinder opening 27 and flows into the first and second combustion support gas. Titanium oxide deposits were generated on the hollow inner quartz tube, and quartz glass was damaged by the blockage of the flow path.
On the other hand, in Examples 1 to 12 in which the preheated titanium tetrachloride-containing gas and the first gas G2 do not contain oxygen and water vapor, titanium oxide deposits on the first and second hollow inner quartz tubes are generated. Thus, it was found that production with a high yield of 95% or more was possible for a long time, at least 100 hours in total.

In Examples 1 to 4, the characteristics of the titanium oxide particles obtained were compared by changing the flow rate of the first gas G2 to change the residence time of the first combined gas in the first zone B.
When the length was increased from 47 milliseconds to 47 milliseconds (Example 3) and 75 milliseconds (Example 4) to 32 milliseconds in Example 1, the rutile ratio slightly increased from 4% to 6% to increase the photocatalytic activity. Decreased slightly. On the contrary, when it was shortened to 27 milliseconds (Example 2), the photocatalytic activity was slightly lowered although the rutile ratio was slightly lowered.
In Examples 1 and 5 to 7, the characteristics of titanium oxide particles obtained by changing the titanium tetrachloride concentration (volume%) in the first combined gas by changing the flow rate of titanium tetrachloride were compared. In Example 5 in which the concentration of titanium tetrachloride in the first combined gas was 0.6% compared to 3.8% in Example 1, the BET value increased and the photocatalytic activity slightly increased. When the concentration of titanium tetrachloride in the first combined gas is increased to 5.9% (Example 6) and 13.6% (Example 7) with respect to 3.8% of Example 1, The BET value decreased from 14 m ² / g to 9 m ² / g and the rutile ratio increased from 4% to 8%. As a result, the photocatalytic activity decreased. Accordingly, the titanium tetrachloride concentration in the first combined gas is preferably 0.1 to 20% by volume, more preferably 0.5 to 10% by volume, and 0.5 to 5% by volume. More preferably.
In Examples 1 and 8, the characteristics of titanium oxide particles obtained by changing the preheating temperature of the first gas G2 were compared. In Example 8 where the preheating temperature of the first gas G2 was 1010 ° C., in Example 8 where the preheating temperature was 900 ° C., the rutile ratio was the same as in Example 1, and the photocatalytic activity was relatively high.

  In order to obtain higher photocatalytic activity than in Examples 1 and 8, the preheating temperature of the first gas G2 is preferably in the range of 800 ° C. or higher and 1050 ° C. or lower, and more preferably in the range of 850 ° C. or higher and 1050 ° C. or lower. preferable.

Using Examples 1 and 8 to 10, the characteristics of titanium oxide particles obtained by changing the preheating temperature of the second gas G3 were compared. In contrast to Example 8 in which the preheating temperature of the first gas G2 is 900 ° C. and the preheating temperature of the second gas G3 is 1030 ° C., the preheating temperature of the first gas G2 is 900 ° C., and the preheating temperature of the second gas G3 is 950. In Example 9, which was set to ° C., the photocatalytic activity was slightly reduced, although the rutile ratio was slightly decreased. In Example 10 in which the preheating temperature of the second gas G3 was 1100 ° C., the rutile ratio was higher as compared to Example 1 in which the preheating temperature was 1030 ° C. As a result, the decahedral ratio was reduced and the photocatalytic activity was reduced.
Accordingly, the preheating temperature of the second gas G3 is preferably in the range of 900 ° C. or higher and 1100 ° C. or lower, and more preferably in the range of 950 ° C. or higher and 1050 ° C. or lower.

Using Examples 1, 11, and 12, the characteristics of titanium oxide particles obtained by changing the temperature of the metal chloride-containing gas G1 were compared. When the temperature was raised to 980 ° C. (Example 11) with respect to 880 ° C. in Example 1, the rutile ratio slightly increased from 4% to 5%, and the photocatalytic activity was lowered.
Conversely, when the temperature was lowered to 650 ° C., the rutile ratio decreased from 4% to 3%, and the photocatalytic activity was relatively high.
Accordingly, the preheating temperature of the metal chloride-containing gas G1 is preferably in the range of 600 ° C. or higher and 1000 ° C. or lower, more preferably in the range of 600 ° C. or higher and 950 ° C. or lower, and 800 ° C. or higher and 950 ° C. or lower. More preferably, it is in the range.

  Using Examples 1, 8, 11, and 12, the characteristics of the titanium oxide particles obtained by changing the temperature of the first combined gas were compared.

  In Example 8, the temperature of the first combined gas was lowered by lowering the preheating temperature of the first gas G2 than in Example 1. Specifically, the temperature of the first combined gas in Example 1 was 979 ° C., whereas the temperature of the first combined gas was lowered to 895 ° C. in Example 8, but a relatively high photocatalytic activity was obtained. It was.

  In Example 12, the temperature of the first combined gas was lowered by lowering the preheating temperature of the metal chloride-containing gas G1 than in Example 1. Specifically, the temperature of the first combined gas in Example 1 was 979 ° C., whereas the temperature of the first combined gas was lowered to 925 ° C. in Example 12, but a relatively high photocatalytic activity was obtained. It was.

In Example 11, the temperature of the first combined gas was raised by raising the preheating temperature of the metal chloride-containing gas G1 than in Example 1. In Example 1, the rutile ratio was 4% when the temperature of the first combined gas was 979 ° C., whereas the rutile ratio was increased in Example 11 when the temperature of the first combined gas was increased to 1003 ° C. The photocatalytic activity decreased to 5%.
Accordingly, the temperature of the first combined gas is preferably in the temperature range of 800 ° C. or higher and 1050 ° C. or lower, more preferably in the temperature range of 850 ° C. or higher and 1000 ° C. or lower, and still more preferably 900 ° C. or higher and 1000 ° C. or lower. .

In Examples 1, 9, and 10, characteristics of titanium oxide particles obtained by changing the temperature of the second combined gas were compared. In Example 1, the temperature of the second combined gas was set to 1020 ° C., whereas in Example 9, the temperature of the second combined gas was lowered to 939 ° C., but the photocatalytic activity was only slightly reduced.
In Example 1, the rutile ratio was 4% when the temperature of the second combined gas was 1020 ° C., whereas in Example 10, the temperature of the second combined gas was increased to 1076 ° C. The rutile ratio increased to 12%, and the photocatalytic activity decreased significantly.
Accordingly, the temperature of the second combined gas is preferably in the temperature range of 800 ° C. or higher and 1100 ° C. or lower, more preferably in the temperature range of 800 ° C. or higher and 1050 ° C. or lower, and still more preferably 850 ° C. or higher and 1050 ° C. or lower. .

  The present invention relates to a method for producing metal oxide particles and an apparatus for producing the same, and more particularly to a method for producing titanium oxide particles capable of producing titanium oxide having high photocatalytic activity for a long time. Therefore, it can be used in the photocatalyst industry.

DESCRIPTION OF SYMBOLS 1 ... Hollow outer cylinder, 1a ... Upstream side, 1b ... Downstream side, 2 ... Heat insulation material (ceramic fiber), 3 ... Product recovery part, 3a ... Exhaust pump, 3b ... Pressure adjustment valve, 4 ... 1st hollow inner cylinder 4a ... upstream side, 4b ... downstream end (first joining point), 5 ... second hollow inner cylinder, 5a ... upstream side, 5b ... downstream end (second joining point), 6 ... discharge pipe, 11 ... reaction pipe 15 ... 1st conduit, 16 ... 2nd conduit, 24 ... 1st hollow inner cylinder opening part, 25, 26 ... Ring-shaped opening part, 27 ... 2nd hollow inner cylinder opening part, 28 ... Hollow outer cylinder opening part, DESCRIPTION OF SYMBOLS 101 ... Manufacturing apparatus of metal oxide particle, A ... 2nd reaction zone, B ... 1st zone, G1 ... Metal chloride containing gas, G2 ... 1st gas, G3 ... 2nd gas, X ... Preheating area | region, Y ... Preheating area, Z ... Preheating area.

Claims (14)

In the reaction tube, the preheated metal chloride-containing gas is joined with the preheated first gas not containing the metal chloride at the first joining point to form a first joining gas, and the first joining gas includes A method for producing metal oxide particles, comprising the step of joining a preheated second gas that does not contain metal chloride at a second joining point that is further downstream than the first joining point to form a second joining gas. Because
Both the metal chloride-containing gas and the first gas do not contain oxygen or water vapor,
The second gas contains at least oxygen;
From the first joining point to the second joining point, the preheating temperature of the first gas is set to a temperature equal to or higher than the preheating temperature of the metal chloride-containing gas, and the first gas is joined at the first joining point. (Referred to as the first zone), the preheated metal chloride-containing gas is further heated, and the preheating temperature of the second gas is set to a temperature equal to or higher than the temperature of the first combined gas. The first combined gas is further heated on the downstream side from the second joining point by joining together with the metal oxide particle manufacturing method.   2. The method for producing metal oxide particles according to claim 1, wherein the metal chloride is titanium tetrachloride, and the metal oxide particles are titanium oxide particles.   The method for producing metal oxide particles according to claim 2, wherein the titanium oxide particles are decahedral titanium oxide particles.   The method for producing metal oxide particles according to any one of claims 1 to 3, wherein a preheating temperature of the metal chloride-containing gas is 600 ° C or higher and 1000 ° C or lower.   The temperature of the said 1st combined gas is 800 degreeC or more and 1050 degrees C or less, The manufacturing method of the metal oxide particle of any one of Claims 1-3 characterized by the above-mentioned.   The method for producing metal oxide particles according to claim 1, wherein the temperature of the second combined gas is 800 ° C. or higher and 1100 ° C. or lower.   The method for producing metal oxide particles according to any one of claims 1 to 3, wherein a preheating temperature of the first gas is 800 ° C or higher and 1050 ° C or lower.   The method for producing metal oxide particles according to any one of claims 1 to 3, wherein a preheating temperature of the second gas is 900 ° C or higher and 1100 ° C or lower.   The said metal chloride containing gas contains nitrogen gas, The manufacturing method of the metal oxide particle of any one of Claims 1-3 characterized by the above-mentioned.   The said 1st gas contains 1 or more types of gas chosen from the group which consists of nitrogen gas and argon, The manufacturing method of the metal oxide particle of any one of Claims 1-3 characterized by the above-mentioned.   The metal oxide according to any one of claims 1 to 3, wherein the second gas contains one or more gases selected from the group consisting of nitrogen gas, argon and water vapor together with oxygen gas. Method for producing product particles.   4. The method for producing metal oxide particles according to claim 2, wherein the concentration of the titanium tetrachloride contained in the first combined gas is 0.1 to 20% by volume. 5.   The method for producing metal oxide particles according to any one of claims 1 to 3, wherein a time during which the first combined gas stays in the first zone is 2 to 100 milliseconds.   The method for producing metal oxide particles according to any one of claims 1 to 3, wherein the Reynolds number of the second combined gas is 10 to 10,000.