Gas ejection device and producing method of titanium dioxide powder

Abstract

To provide a gas ejection device capable of increasing a specific surface area of titanium dioxide powder, with a relatively simple structure and, a producing method of titanium dioxide powder.SOLUTION: A gas ejection device 1 of this invention is used in a reaction to generate titanium oxide powder from titanium halide gas Gt in a gas phase, and is equipped with gas flow paths that individually allow multiple types of gases, including titanium halide gas Gt and reaction gas Gr, to flow inside. It includes a nozzle 3 that ejects the multiple types of gases from each ejection port 6, and has adjacent titanium halide gas flow path 4 and reaction gas flow path 5. At the ejection port 6 of the nozzle 3, a direction adjustment section 7 is provided to tilt the ejection direction of the reaction gas Gr towards the titanium halide gas Gt side.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a gas ejection device used in a reaction for producing titanium oxide powder from a titanium halide gas in a gas phase, and a method for producing titanium oxide powder using the same. [Background technology]

[0002] Titanium oxide powder has high whiteness and hiding power, and also exhibits catalytic action when irradiated with light, and also has excellent properties such as dispersibility, weather resistance, chemical stability, etc. For this reason, titanium oxide powder is not only used primarily as a white pigment and ultraviolet shielding filler, but is also widely used in a variety of other applications, including photocatalysis.

[0003] In recent years, titanium dioxide powder has been rapidly applied to the fields of electronic devices and components. For example, barium titanate made from titanium dioxide powder is used as a ferroelectric material in multilayer ceramic capacitors (MLCC, Multi-layer Ceramic Capacitors) and PTC thermistors (Positive Temperature Coefficient Thermistors).

[0004] Titanium oxide powder may be produced by a so-called gas phase method, in which titanium halide gas is mixed with water vapor, oxygen gas, an inert gas, or the like in a gas phase and reacted to produce titanium oxide. An example of this type of technology is described in Patent Document 1.

[0005] Patent Document 1 proposes a method for producing anatase-type titanium oxide powder, which is characterized in that "titanium tetrachloride, oxygen, hydrogen and water vapor are preheated to 450-650°C, and then the preheated titanium tetrachloride, oxygen, hydrogen and water vapor are reacted under gas-phase reaction conditions by supplying 60-90 L of oxygen gas, 60-90 L of hydrogen gas and 240-600 L of water vapor per 1 L of titanium tetrachloride," with the aim of "providing a titanium oxide powder having a large specific surface area and a lower rutilated ratio than titanium oxide powder, and a method for producing the same." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4739187 Summary of the Invention [Problem to be solved by the invention]

[0007] In the gas phase method as described above, multiple types of gases including titanium halide gas and reactive gases such as oxygen gas and water vapor are individually flowed inside the nozzle of the gas ejection device, and these gases are ejected from the ejection port at the tip side in the gas flow direction. At this time, the titanium halide gas ejected from the nozzle ejection port reacts with the reactive gas ejected together with it, and the reaction turns into titanium oxide powder.

[0008] However, for example, titanium oxide powder used in the fields of electronic devices and parts may be required to be fine and have a relatively large specific surface area. It is desirable to be able to produce titanium oxide powder with a large specific surface area without requiring significant changes to current equipment.

[0009] The present invention is intended to address these problems, and has as its object to provide a gas ejection device and a method for producing titanium oxide powder that have a relatively simple structure and are capable of increasing the specific surface area of ​​titanium oxide powder. [Means for solving the problem]

[0010] After extensive research, the inventors have found that narrowing the titanium halide gas flow path inside the nozzle of the gas ejection device makes it easier for the titanium halide gas ejected from the nozzle to mix with the reactive gas, increasing the reaction efficiency. However, narrowing the titanium halide gas flow path increases the internal pressure and increases the load on the equipment when the flow rate is increased to a certain extent for mass production. In response to this, the inventors have found that by ejecting the reactive gas at an angle toward the titanium halide gas at the nozzle outlet of the gas ejection device, the reaction efficiency with the reactive gas is increased and titanium oxide powder with a large specific surface area can be obtained without narrowing the titanium halide gas flow path that much.

[0011] The gas ejection device of the present invention is used for a reaction in which titanium oxide powder is produced from titanium halide gas in the gas phase, and is provided with gas flow paths within which multiple types of gases including titanium halide gas and reactive gas flow individually, and a nozzle for ejecting the multiple types of gases from each ejection port, the gas flow path having a titanium halide gas flow path and a reactive gas flow path positioned adjacent to each other, and a direction adjustment section is provided at the nozzle ejection port for tilting the ejection direction of the reactive gas toward the titanium halide gas side with respect to the ejection direction of the titanium halide gas.

[0012] In the above gas ejection device, at least the titanium halide gas flow path and the reactant gas flow path among the gas flow paths may be concentrically arranged in a cross section perpendicular to the flow direction of the titanium halide gas inside the nozzle.

[0013] In this case, in a cross section perpendicular to the flow direction of the titanium halide gas inside the nozzle, the titanium halide gas flow path may be located at the radial center of the gas flow path, and the reactant gas flow path may be located surrounding the titanium halide gas flow path.

[0014] In this case, it is preferable that the direction adjustment portion includes an inclined surface on the inner surface on the outer circumferential side that defines the reactive gas flow path, inclined in a direction approaching the titanium halide gas flow path as it moves toward the outlet side with respect to the direction of the titanium halide gas ejection.

[0015] The inclination angle of the inclined surface with respect to the ejection direction of the titanium halide gas is preferably 5° to 15° on the acute angle side.

[0016] In the above gas ejection device, the titanium halide gas passage may be a titanium tetrachloride gas passage, and the reactant gas passage may be a water vapor passage.

[0017] The method for producing titanium oxide powder of the present invention uses any one of the gas ejection devices described above. Effect of the Invention

[0018] According to the present invention, the specific surface area of ​​titanium oxide powder can be increased with a relatively simple structure. [Brief description of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view taken along a gas flow direction, showing a gas ejection device according to an embodiment of the present invention. [Diagram 2] 2 is an enlarged cross-sectional view showing a main part including a nozzle of the gas ejection device of FIG. 1. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] 3 is a cross-sectional view similar to FIG. 2, showing a modified example of the nozzle of the gas ejection device. [Diagram 5] 2 is a cross-sectional view similar to FIG. 1, showing a gas ejection device of a comparative example. [Figure 6] 1 is a graph showing the specific surface area at each dilution ratio of the titanium oxide powders obtained in the Examples and Comparative Examples. [Figure 7] 1 is a graph showing the rutilated ratio at each dilution ratio of the titanium oxide powders obtained in the Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0021] (Gas ejection device) The gas ejection device 1 shown in Fig. 1 ejects a plurality of gases including a titanium halide gas Gt and a reactive gas Gr at a predetermined high temperature, and then contacts the titanium halide gas Gt with the reactive gas Gr in the gas phase after ejection, thereby producing titanium oxide powder from the titanium halide gas Gt. The gas ejection device 1 may be called a combustion burner.

[0022] The gas ejection device 1 includes a main body 2 and a nozzle 3 through which multiple types of gases including a titanium halide gas Gt and a reactive gas Gr flow. Inside the main body 2 and the nozzle 3, gas flow paths are provided so that the multiple types of gases can flow individually, and the multiple types of gases are ejected to the outside from an ejection port 6 located at the most distal end (lower side in FIG. 1) in the flow direction of the titanium halide gas (also simply referred to as the "gas flow direction"), which corresponds to the vertical direction in FIG. 1, inside the nozzle 3. The ejection ports 6 are located at the most distal end of the nozzle 3, with the number and positions corresponding to the gas flow paths through which the multiple types of gases flow.

[0023] The gas flow passages include a titanium halide gas flow passage 4 through which a titanium halide gas Gt flows, and a reactant gas flow passage 5 through which a reactant gas Gr flows. The titanium halide gas flow passage 4 and the reactant gas flow passage 5 are provided inside the gas ejection device 1 at adjacent positions in a cross section perpendicular to the gas flow direction.

[0024] Here, the illustrated gas ejection device 1 is provided with a direction adjustment unit 7 at the ejection port 6 of the nozzle 3, which tilts the ejection direction of the reactive gas Gr toward the titanium halide gas Gt with respect to the ejection direction of the titanium halide gas Gt, as shown by the arrow in Fig. 2. The direction adjustment unit 7 causes the reactive gas Gr ejected from the ejection port 6 to flow in a direction tilted toward the adjacent titanium halide gas Gt.

[0025] This is believed to sufficiently mix the reactive gas Gr with the titanium halide gas Gt, increasing the reaction efficiency between the titanium halide gas Gt and the reactive gas Gr. As a result, fine titanium oxide powder with a large specific surface area can be produced in the reaction region in front of the nozzle 3.

[0026] In addition, in order to obtain titanium oxide powder with a large specific surface area by the gas phase method, it is also possible to flow titanium halide gas diluted with an inert gas such as nitrogen gas into the inside of the nozzle and eject it from the nozzle outlet, thereby reducing the chance of grain growth when reacting with the reactive gas. However, if the titanium halide gas is too diluted, it is necessary to greatly increase the flow rate of the titanium halide gas in order to realize mass production of titanium oxide powder, which may lead to an increase in the size of the equipment and a possibility of an increase in the load on the processing equipment after the production of the titanium oxide powder. In contrast, in this embodiment, as described above, it is possible to obtain titanium oxide powder with a large specific surface area with a relatively simple structure in which the direction adjustment unit 7 is provided at the nozzle outlet 6 of the nozzle 3 to tilt the ejection direction of the reactive gas Gr toward the titanium halide gas Gt side. The titanium halide gas may be diluted, but it is not necessary to dilute it at a very high dilution rate, and the specific surface area of ​​the titanium oxide powder can be increased.

[0027] In addition, when the reaction efficiency is increased by injecting the reactive gas Gr toward the titanium halide gas Gt using the direction adjustment unit 7, the titanium oxide powder containing TiO2 has a low rutilated ratio, although the reason is not necessarily clear. Therefore, this embodiment is suitable for producing titanium oxide powder with a low rutilated ratio.

[0028] In the illustrated embodiment, the titanium halide gas flow passage 4 and the reactive gas flow passage 5 are concentrically arranged inside the nozzle 3 of the gas ejection device 1 as shown in Fig. 3 in a cross section perpendicular to the gas flow direction. In particular, in this embodiment, the titanium halide gas flow passage 4 is located at the radial center of the gas flow passage in a cross section perpendicular to the gas flow direction, and the reactive gas flow passage 5 is a cylindrical space that surrounds the titanium halide gas flow passage 4 and is located adjacent to the outer periphery of the titanium halide gas flow passage 4.

[0029] In order to realize the above-mentioned arrangement of the titanium halide gas flow passage 4 and the reactive gas flow passage 5, the gas ejection device 1 is configured by concentrically arranging an inner cylinder 8 and an outer cylinder 9, which have different outer diameters, on the inner and outer circumferential sides, respectively. The titanium halide gas flow passage 4 is defined by the inner peripheral surface of the inner cylinder 8, and the reactive gas flow passage 5 is defined between the outer peripheral surface of the inner cylinder 8 (the inner surface on the inner peripheral side as viewed from the reactive gas flow passage 5) and the inner peripheral surface of the outer cylinder 9 (the inner surface on the outer peripheral side as viewed from the reactive gas flow passage 5).

[0030] However, although not shown in the figures, it is also possible to provide a gas flow path for another gas in the center of the concentric titanium halide gas flow path and the reactant gas flow path or between them. Also, although not shown in the figures, a titanium halide gas flow path and a non-cylindrical reactant gas flow path may be provided in parallel. Even in such an arrangement of the gas flow paths, by providing the above-mentioned direction adjustment unit, it is expected that the reaction efficiency between the titanium halide gas and the reactant gas will be improved, and the titanium oxide powder will be finer as a result.

[0031] Here, of the inner surface on the inner periphery side and the inner surface on the outer periphery side which define the reactive gas flow passage 5, the part of the inner surface on the outer periphery side (the inner surface of the outer cylinder 9) on the side of the nozzle 6 is formed as an inclined surface 10 which is inclined in a direction approaching the titanium halide gas flow passage 4 as it approaches the nozzle 6 side over the entire circumference with respect to the ejection direction of the titanium halide gas Gt. The direction adjustment unit 7 is mainly configured to include this inclined surface 10. The inclined surface 10 guides the reactive gas Gr ejected from the ejection port 6 so that it is ejected at an incline toward the titanium halide gas Gt side, so that the ejection direction of the reactive gas Gr can be effectively adjusted.

[0032] The inclination angle θ of the inclined surface 10 with respect to the ejection direction of the titanium halide gas Gt is preferably 5° to 15° on the acute angle side. By not making the inclination angle θ of the inclined surface 10 too large, the distance that the gas flows along the inclined surface 10 can be secured, and the direction of the gas can be reliably changed. Also, by not making the inclination angle θ of the inclined surface 10 too small, the reactive gas Gr can be quickly distributed to the center portion.

[0033] 2, the outer peripheral surface of the outer cylinder 9 is similarly inclined to match the inclined surface 10 on the inner peripheral surface of the outer cylinder 9 to form an inclined wall portion 11, and the thickness of the outer cylinder 9 is substantially constant over almost the entirety in the gas flow direction. On the other hand, as shown in FIG. 4(a), the inner peripheral surface of the outer cylinder 9 may be inclined while the outer peripheral surface is not inclined, for example, by making the outer diameter of the outer cylinder 9 constant.

[0034] The inclined surface 10 may be linearly inclined in cross section along the gas flow direction as in the illustrated example, or may be curved or stepped inclined, although not shown.

[0035] Furthermore, the length Le of the inclined surface 10 of the outer cylinder 9 along the gas flow direction can be, for example, 1.8 to 2.0 times the inner diameter of the outer cylinder 9 at the nozzle 6. The length Le of the inclined surface 10 of the outer cylinder 9 along the gas flow direction may be determined so that the flow path cross-sectional area of ​​the reactant gas flow path 5 at the tip side portion having the inclined surface 10 is about 1 / 3 of that at the upper portion not having the inclined surface 10.

[0036] In the illustrated example, following the above-mentioned inclined surface 10 of the outer cylinder 9, the inner and outer circumferential surfaces of the inner cylinder 8 at the nozzle outlet 6 side of the nozzle 3 are also inclined toward the center in the radial direction, and an inclined wall portion 12 is also provided on the inner cylinder 8. Providing the inclined wall portion 12 on the inner cylinder 8 in this manner is preferable because the width or diameter of the titanium halide gas Gt ejected from the nozzle outlet 6 becomes smaller, and the titanium halide gas Gt can be sufficiently reacted with the reactive gas Gr even in the vicinity of the center in the radial direction.

[0037] The inclination angle of the inclined wall portion 12 of the inner cylinder 8 can be substantially the same as the inclination angle θ of the above-mentioned inclined surface 10. The length Li of the inclined wall portion 12 of the inner cylinder 8 along the gas flow direction can be, for example, 2.1 to 2.2 times the inner diameter of the inner cylinder 8 at the nozzle 6. The length Li of the inclined wall portion 12 of the inner cylinder 8 along the gas flow direction can be determined so that the flow path cross-sectional area of ​​the titanium halide gas flow path 4 at the tip side portion having the inclined wall portion 12 is about 1 / 3 of the upper portion not having the inclined wall portion 12.

[0038] However, as shown in FIG. 4(b), the inner cylinder 8 may not have an inclined wall portion, and the inner and outer diameters at the nozzle 3 may be constant.

[0039] Also, instead of or in addition to providing the inclined surface 10 on the inner surface on the outer circumferential side of the reactive gas flow passage 5 in the nozzle 3 itself as described above, a separate cylindrical tapered member 13 for guiding the reactive gas Gr ejected from the ejection port 6 to the titanium halide gas Gt side may be attached to the ejection port 6 of the nozzle 3 as shown in Fig. 4(c). In Fig. 4(c), the inner peripheral surface of the cylindrical tapered member 13 is formed as the inclined surface 10, and although not shown, if the cylindrical tapered member has an inner diameter smaller than the inner diameter of the outer cylinder 9, the reactive gas Gr ejected from the ejection port 6 can be directed to the titanium halide gas Gt side even if the inner diameter of the cylindrical tapered member is constant in the gas flow direction.

[0040] As another direction adjustment part, although not shown, it is possible to adopt a gas injection part that is arranged outside the width direction or radial direction of the nozzle outlet of the reactive gas and injects a gas such as an inert gas inward in the width direction or radial direction toward the reactive gas. The reactive gas ejected from the nozzle outlet is expected to be blown from its side by the gas injected inward from the gas injection part, so that it flows inclined toward the titanium halide gas adjacent to the inside. However, if gas is injected from the above gas injection part, the reactive gas may be diluted by the gas and the reactivity with the titanium halide gas may decrease. From this point of view, it is preferable to configure the direction adjustment part 7 with an inclined surface 10 as described above.

[0041] Typically, the titanium halide gas flow passage 4 can be a titanium tetrachloride gas flow passage that flows titanium tetrachloride gas among titanium halide gas Gt. Titanium tetrafluoride (TiF4), titanium tetrabromide (TiBr4), titanium tetraiodide (TiI4), etc. can also be used as the titanium halide gas Gt. The reactive gas flow passage 5 is preferably a water vapor flow passage that flows highly reactive water vapor among oxygen gas, water vapor, etc. In the gas ejection device 1 shown in FIG. 1, the reactive gas Gr is supplied to the reactive gas flow passage 5 from a supply pipe 14 connected to the outer cylinder 9 from the outer periphery at the base end side (upper side in FIG. 1) in the gas flow direction. The base end side portion of the outer cylinder 9 to which the supply pipe 14 is connected is shaped so that the inner and outer diameters gradually decrease toward the base end side. However, such detailed shapes are not limited to those shown in the figures.

[0042] (Method of manufacturing titanium oxide powder) The above-mentioned gas ejection device 1 can be used to produce titanium oxide powder mainly containing TiO2 from titanium chlorides such as titanium tetrachloride (TiCl4) or other titanium halide gases Gt by a gas phase method.

[0043] More specifically, a plurality of gases including titanium halide gas Gt and reactive gas Gr such as oxygen gas and water vapor are preheated and then supplied to each gas flow path of the gas ejection device 1 in the reactor. In addition to the titanium halide gas Gt and reactive gas Gr, hydrogen gas and / or an inert gas may also be supplied. Titanium halide gas Gt diluted with an inert gas may also be used.

[0044] After passing through each gas passage, the multiple gases are ejected from the ejection port 6 of the nozzle 3. At this time, the multiple gases are mixed in the flame at a predetermined high temperature, and the titanium halide gas Gt comes into contact with the reactive gas Gr.

[0045] Here, titanium oxide powder containing TiO2 is produced by the reaction between titanium halide gas Gt and reactive gas Gr. When titanium tetrachloride gas is used as the titanium halide gas Gt and oxygen gas or water vapor is used as the reactive gas Gr, the reactions represented by the reaction formulas TiCl4+O2→TiO2+2Cl2 and TiCl4+2H2O→TiO2+4HCl occur.

[0046] The reaction temperature may be any temperature at which TiO2 is produced, and may be, for example, 600°C to 1100°C.

[0047] The titanium oxide powder produced by the above reaction is cooled by contacting it with a cooling gas such as air, and then separated from the gas and collected.

[0048] Thereafter, if necessary, a treatment for removing chlorine, crushing, and classification such as sieving can be carried out to produce titanium oxide powder. EXAMPLES

[0049] Next, a gas ejection device according to the present invention was prototyped and its effects were confirmed, which will be described below. However, the description here is merely for illustrative purposes and is not intended to be limiting.

[0050] 1 to 3 was fabricated as an example, and titanium oxide powder was produced using this. In this gas ejection device, the inclination angle θ of the inclined surface was set to 10°, the length Le of the inclined surface of the outer cylinder along the gas flow direction was set to 31.5 mm, and the length Li of the inclined wall of the inner cylinder along the gas flow direction was set to 17.4 mm.

[0051] In the production of titanium oxide powder, titanium tetrachloride gas was diluted with nitrogen gas and preheated to 900°C, and then this was supplied to the gas ejection device in the reactor together with steam preheated to 900°C. The mixed gas ejected from the nozzle of the gas ejection device reached a reaction temperature of approximately 1000°C in the reactor, and titanium oxide powder was obtained by the reaction. The titanium oxide powder obtained in the reactor was then collected and cooled, and the chlorine was removed before being crushed and sieved.

[0052] Here, multiple tests were conducted by changing the flow rates of titanium tetrachloride gas and nitrogen gas to change the dilution rate of titanium tetrachloride with nitrogen gas (the ratio of the amount of nitrogen gas to the amount of titanium tetrachloride gas).

[0053] In the comparative example, titanium oxide powder was produced under substantially the same conditions as in the example, except that a gas ejection device was used in which the inner and outer cylinders of the nozzle did not have inclined walls and their inner and outer diameters were constant, as shown in Figure 5.

[0054] The specific surface area and rutilated ratio of the titanium oxide powders obtained in the Examples and Comparative Examples were confirmed. The specific surface area was measured by the BET method, and the rutilated ratio was measured by the X-ray diffraction method. The results are shown in Figures 6 and 7.

[0055] It can be seen from Fig. 6 that, regardless of the dilution ratio, the titanium oxide powder obtained in the Examples had a larger specific surface area than the Comparative Examples. Moreover, as shown in Fig. 7, regardless of the dilution ratio, the titanium oxide powder obtained in the Examples had a lower rutilated ratio than the titanium oxide powder obtained in the Comparative Examples.

[0056] From the above, it was found that according to the present invention, titanium oxide powder having a relatively large specific surface area can be obtained. [Explanation of symbols]

[0057] 1 Gas ejection device 2 Main unit 3 Nozzles 4. Titanium halide gas flow path 5. Reaction gas flow path 6 spout 7 direction adjustment section 8 Inner cylinder 9 Outer cylinder 10 Slope 11 Slanted wall section 12 Slanted wall section 13 Cylindrical tapered member 14 Supply pipe Gr reaction gas Gt Titanium halide gas θ Tilt angle

Claims

1. A gas ejection device used in a reaction for producing titanium oxide powder from a titanium halide gas in a gas phase, comprising: a gas passage for passing a plurality of types of gases including a titanium halide gas and a reactive gas therethrough, and a nozzle for ejecting the plurality of types of gases from each of the ejection ports; the gas flow passage has a titanium halide gas flow passage and a reactant gas flow passage positioned adjacent to each other; The gas ejection device has a direction adjusting section at the nozzle outlet for tilting the ejection direction of the reactive gas toward the titanium halide gas with respect to the ejection direction of the titanium halide gas.

2. 2. The gas ejection device according to claim 1, wherein at least the titanium halide gas flow passage and the reactant gas flow passage are concentrically arranged in a cross section perpendicular to the flow direction of the titanium halide gas inside the nozzle.

3. 3. The gas ejection device according to claim 2, wherein in a cross section perpendicular to the flow direction of the titanium halide gas inside the nozzle, the titanium halide gas flow passage is located at the radial center of the gas flow passage, and the reactant gas flow passage is located surrounding the titanium halide gas flow passage.

4. 3. The gas ejection device according to claim 2, wherein the direction adjustment portion includes an inclined surface on an inner surface on an outer circumferential side that defines the reactant gas flow path, the inclined surface being inclined in a direction approaching the titanium halide gas flow path as it approaches the ejection port side with respect to the ejection direction of the titanium halide gas.

5. 5. The gas ejection device according to claim 4, wherein the inclination angle of the inclined surface with respect to the ejection direction of the titanium halide gas is 5° to 15° on the acute angle side.

6. 2. The gas ejection device according to claim 1, wherein the titanium halide gas passage is a titanium tetrachloride gas passage, and the reactant gas passage is a water vapor passage.

7. A method for producing titanium oxide powder, using the gas ejection device according to any one of claims 1 to 6.

Images