KR100991754B1 - Preparation method of nano-sized TiO2 powder during the decomposition of CO2 by thermal plasma - Google Patents

Abstract

The present invention comprises the steps of injecting carbon dioxide and vaporized titanium tetrachloride as a reaction gas into the reaction tube of the thermal plasma jet apparatus (step 1); Decomposing the injected carbon dioxide into a thermal plasma jet generated using argon gas to react with titanium tetrachloride carried by the carrier gas (step 2); And a method for producing titanium dioxide nanoparticles simultaneously with the decomposition of carbon dioxide by thermal plasma, which comprises the step of preparing titanium dioxide nanoparticles by cooling the produced titanium dioxide nanoparticles, and the titanium dioxide nanoparticles produced thereby. As the method according to the present invention decomposes carbon dioxide as a reaction gas, it may help to alleviate global warming, and there is no need to consider a post-treatment process by using a thermal plasma having characteristics such as high temperature and high activity. However, there is no fear of the generation of secondary pollutants, and it can decompose carbon dioxide in a short time, and thus the efficiency is also superior to other methods, and titanium dioxide synthesized by the method according to the present invention is simply reacted with oxygen, and thus, It has excellent photocatalytic activity in the ultraviolet / visible region and is 20 ~ 50 nm Since it has a high specific surface area and anatase phase as a knock, it can be usefully used as a photocatalyst.

Thermal Plasma, Carbon Dioxide, Titanium Dioxide Synthesis

Description

Method for preparing titanium dioxide nanoparticles simultaneously with carbon dioxide decomposition by thermal plasma {Preparation method of nano-sized TiO2 powder during the decomposition of CO2 by thermal plasma}

The present invention relates to a method for producing titanium dioxide nanoparticles simultaneously with the decomposition of carbon dioxide by thermal plasma.

Increasing CO2 emissions are considered to be a major factor in global warming. This has a major impact on rising atmospheric temperatures, climate change, and ecosystem impacts, so the treatment of carbon dioxide remains an important challenge in mitigating global warming.

On the other hand, titanium dioxide (TiO ₂ ) is very stable chemically and photochemically, has been attracting attention as an environmentally friendly material due to strong oxidation and harmlessness. The titanium dioxide is generally used as a photocatalyst for removing environmental pollutants, a raw material of pigments, a plastic additive, or a multi-coating agent for glasses, and has two crystal phases, an anatase phase and a rutile phase.

Titanium dioxide on anatase is used as a photocatalyst in systems such as photolysis of acetone, phenol and trichloroethylene, or oxidation of nitrogen oxides such as nitrogen monoxide or nitrogen dioxide and solar energy conversion systems.

Rutile titanium dioxide is widely used as a material for white pigments because of its excellent UV-scattering effect.It has higher dielectric constant and refractive index than other materials, as well as excellent adsorption and coloring ability of oil, and chemicals in strong acidity and strong basicity. It has been used in optical coatings, beam splitters, anti-reflective coatings, and the like. In addition, since titanium dioxide has a wide chemical stability and a non-stoichiometric phase region, and shows various electrical characteristics according to oxygen partial pressure, it is being studied as a component of humidity sensor and high temperature oxygen sensor, and its application field is gradually expanding.

Common methods for producing titanium dioxide reported so far include the chloride process (gas phase method) and the sulfate process (sulfate process).

The chloride process was industrialized by Du Pont in the US in 1956. The chloride process is based on titanium tetrachloride (TiCl ₄ ), which reacts with moisture in the air to cause severe hydrolysis reactions. It is made, the obtained titanium dioxide particles are fine but coarse, and the production cost of the product is high due to the need for an auxiliary protection device equipment due to corrosive gases (HCl, Cl ₂ ) generated during the reaction.

The sulfate process uses titanium sulfate (TiSO ₄ ), commercialized by Titan Co., Norway, in 1916 as a starting material.The amorphous hydroxide obtained after hydrolysis is calcined, and then crushed to obtain titanium dioxide powder. Because of this, there is a problem that the quality of the final product is greatly degraded due to the incorporation of many impurities in this process.

As one of the new liquid phase methods recently introduced, it is described in Russian Patent SU-1398321, and hydrolyzed titanium dioxide is hydrolyzed by heating by adding an appropriate amount of anatase phase precipitate to a titanium tetrachloride solution. Titanium dioxide is prepared by precipitation and post-treatment process of high temperature heat treatment. This process is relatively simple, whereas additional high temperature heat treatment at 600-650 ° C. is required to obtain anatase-like titanium dioxide, and the rutile phase In order to obtain titanium dioxide, there is a disadvantage that a higher temperature heat treatment is required.

In addition, Japanese Patent Application No. Hei 9-124320 discloses one of various kinds of acetate, carbonate, oxalate, and citrate containing alkali metal or alkaline earth metal in a titanium tetrachloride solution dissolved in alcohol such as butanol. After adding together to make a gel, a method of producing titanium dioxide through a high temperature heat treatment process is produced, which uses a third additive such as an ultra-fine titanium dioxide with good physical properties, but expensive organic acid And, there is a problem that a high temperature heat treatment process for removing the added organic acids after the gel production is required again.

In addition to the above-described methods, studies are being actively conducted to control characteristics of the raw material powder of titanium dioxide such as particle shape, particle size, and particle size distribution by sol-gel method, hydrothermal synthesis method, and the like. In order to prepare spherical titanium dioxide powder having a uniform size, a method using a metal alkoxide is mainly used. This sol-gel method forms a powder having a fine spherical uniform size of 1.0 μm or less, but starting materials Phosphorus alkoxide itself causes violent hydrolysis reactions in the air, so the reaction conditions must be strictly controlled. Since alkoxide is expensive, it is currently not commercialized and is progressing to a laboratory scale. In addition, the hydrothermal synthesis method has a good state of the powder obtained by this method, but it is disadvantageous in that the continuous process is not possible because an autoclave that maintains high temperature and high pressure conditions is mainly used.

Therefore, the present inventors have studied to solve the problems in the process of effectively treating the carbon dioxide which is the main factor of global warming and manufacturing the conventional titanium dioxide powder, as a result of decomposing the carbon dioxide using thermal plasma at the same time anatase titanium dioxide nano It was found that the particles could be produced and the present invention was completed.

An object of the present invention is to provide a method for producing anatase type titanium dioxide nanoparticles using thermal plasma.

Another object of the present invention to provide anatase type titanium dioxide nanoparticles prepared by the above method.

In order to achieve the above object, the present invention comprises the steps of injecting carbon dioxide and vaporized titanium tetrachloride as a reaction gas into a reaction tube of the thermal plasma jet apparatus (step 1); Decomposing the injected carbon dioxide into a thermal plasma jet generated using argon gas to react with titanium tetrachloride carried by the carrier gas (step 2); And it provides a method for producing titanium dioxide nanoparticles using a thermal plasma comprising the step (step 3) of cooling the produced titanium dioxide nanoparticles.

The present invention also provides anatase titanium dioxide nanoparticles prepared by the above method.

Since the method according to the present invention decomposes carbon dioxide as a reaction gas, it may help to alleviate global warming, and it is not necessary to consider the post-treatment process by using thermal plasma having characteristics such as high temperature and high activity. There is no concern about the generation of secondary pollutants, and it can decompose carbon dioxide in a short time, so the efficiency is superior to other methods. In addition, titanium dioxide synthesized by the method according to the present invention has superior photocatalytic activity in the ultraviolet / visible region than titanium dioxide synthesized by simply reacting with oxygen, and has a high specific surface area with a nano size of 20 to 50 nm. Since it has an anatase phase, it can be usefully used as a photocatalyst.

Hereinafter, the present invention will be described in more detail.

The present invention comprises the steps of injecting carbon dioxide and vaporized titanium tetrachloride as a reaction gas into a reaction tube of a thermal plasma jet apparatus (step 1);

Decomposing the injected carbon dioxide into a thermal plasma jet generated using argon gas to react with titanium tetrachloride carried by the carrier gas (step 2); And

It provides a method for producing titanium dioxide nanoparticles using thermal plasma comprising the step (step 3) of cooling the produced titanium dioxide nanoparticles.

In one embodiment of the invention, the thermal plasma jet system to be used is 1, the plasma Sat tooth (1) for supplying a heat source for the decomposition of carbon dioxide and; Carbon dioxide and titanium tetrachloride are injected, the reaction tube (2) and cooling tube (3) in which carbon dioxide is decomposed and reacted with titanium tetrachloride, the exhaust section (4) and the torch section (1) for discharging the waste gas generated after the reaction. It consists of a power supply (5) for supplying a power supply, using a direct current as a power source, the voltage is 40 V, the current is used in the range of 150 ~ 200 A. The torch unit 1 uses a tungsten cathode rod and an anode nozzle, and generates a plasma jet by flowing argon gas between the anode nozzle and the cathode rod. In addition, in order to protect the torch part 1 from heat, both electrodes are cooled by water. The reaction tube 2 is a stainless double tube with a window. The gas discharged to the exhaust part 4 is processed through the scrubber 41 and then the decomposition rate of carbon dioxide is measured using the gas chromatography 42.

First, step 1 is a step of injecting carbon dioxide and titanium tetrachloride into the reaction tube of the thermal plasma jet apparatus.

The carbon dioxide is a major factor of global warming, and since the carbon dioxide has a great influence on atmospheric temperature, climate change, and ecosystem destruction, the decomposition of carbon dioxide can help to alleviate global warming, and the decomposed oxygen is titanium dioxide It is a good material to synthesize. At this time, it is preferable to install a mass flow controller (MFC) in the carbon dioxide inlet to check the decomposition rate of carbon dioxide according to the flow rate of the carbon dioxide.

The titanium tetrachloride serves to prevent the recombination of oxygen and carbon in the process of dissociation and recombination of carbon dioxide, and serves as a reactant in the synthesis of titanium dioxide. At this time, since titanium tetrachloride has a low boiling point, since it is easily vaporized even at room temperature, titanium tetrachloride is preferably injected using argon as a carrier gas. At this time, in order to inject a predetermined amount of titanium tetrachloride, it is preferable to maintain the thermostat at about 30 ~ 35 ℃.

In the method according to the invention, the carbon dioxide and titanium tetrachloride may be injected sequentially, or may be injected at the same time. However, in order to improve the decomposition rate of carbon dioxide, it is preferable to simultaneously inject the carbon dioxide and titanium tetrachloride.

In the method according to the invention, the carbon dioxide and titanium tetrachloride are preferably injected in a direction parallel to the plasma jet generation direction. This is because titanium tetrachloride is effectively decomposed in a high temperature plasma region to facilitate the coupling with oxygen atoms.

In the method according to the invention, the carbon dioxide and titanium tetrachloride are preferably injected to a position within 2 mm from the plasma jet nozzle to facilitate decomposition and reaction. If the injection position is out of 2 mm there is a problem that decomposition and reaction according to the plasma does not occur preferably.

Next, step 2 is a step of decomposing and reacting carbon dioxide and titanium tetrachloride in the thermal plasma jet apparatus.

The heat source used in this step is a thermal plasma by a direct current thermal plasma jet device. Thermal plasma is an ionizing gas composed of electrons, ions, atoms and molecules generated from a plasma torch using a direct current arc or a high frequency inductively coupled discharge. It is a form of high speed jet flame with ultra high temperature and high heat capacity ranging from thousands to tens of thousands of K. It is a state of a fourth material which has extreme physicochemical properties that are completely different from solids, liquids and gases.

In the thermal plasma jet apparatus of the present invention, argon gas, air, and nitrogen gas can be used as the heat plasma generating gas, and in particular, argon gas is preferably used. Since argon is a group 8 element, it is easy to emit electrons with relatively little energy and is most widely used for generating thermal plasma because it is an inert gas and has little effect on chemical reactions. An arc is formed by the electrical energy of the cathode and anode of the power supply device of the thermal plasma jet apparatus, and an ultra high temperature plasma of about 10,000 K is generated by argon gas used as the thermal plasma generator gas. The ultra high temperature generated by the thermal plasma is much higher than the temperature generated by the heat treatment method or the combustion method. In addition, argon gas does not react with other reaction gases and does not emit by-products.

In this step, the carbon dioxide and titanium tetrachloride injected in step 1 are decomposed by the thermal plasma generated in the thermal plasma jet apparatus, so that carbon dioxide is ionized to oxygen and carbon, and titanium tetrachloride to chlorine and titanium. At this time, in order to improve the decomposition rate of carbon dioxide decomposed by the thermal plasma, it is preferable to adjust the flow rate of carbon dioxide to 1 ~ 3L / min.

Thus, ionized oxygen and titanium combine to form titanium dioxide.

Next, step 3 is a step of preparing the titanium dioxide nanoparticles by cooling the produced titanium dioxide.

Oxygen element generated by the decomposition of carbon dioxide in step 2 is combined with titanium ionized by thermal plasma, and formed as titanium dioxide nanoparticles by cooling in a cooling tube.

At this time, the cooling process is a step taken in order to affect the crystallization of the titanium dioxide to be formed to produce nano-sized nanoparticles. That is, when the synthesized titanium dioxide is slowly cooled (hereinafter referred to as slow cooling), the particle size of titanium dioxide is increased to more than nano size. Therefore, in the present invention, a step of quenching the synthesized titanium dioxide with cooling water (hereinafter referred to as water cooling) is preferable. At this time, it is necessary to maintain the temperature of the cooling water at 15 to 25 ° C. to rapidly lower the temperature of the vaporized titanium dioxide.

The present invention also provides titanium dioxide prepared according to the above method.

Titanium dioxide prepared according to the above method was found to be nanoparticles of 20 to 50 nm as observed by scanning electron microscope (see FIG. 3 ). As a result of measurement through X-ray diffraction analysis, most of them were found to be anatase phase. (See FIG. 4 ).

Therefore, the titanium dioxide prepared according to the present invention has excellent photocatalytic activity as the anatase phase, and because it is a nano-sized particle, the surface area can be increased to increase the photoactivity, and can be applied as a new function. For example, it can be applied as a conductive material or sensor material by using electrical properties, and can be applied to light absorbers, optical filters, photocatalysts, optical fibers, and infrared sensors by using optical properties.

Hereinafter, the present invention will be described in detail with reference to examples.

However, the following examples are illustrative of the present invention and are not intended to limit the scope of the present invention.

< Example > Thermal Plasma  Used Nanoscale  Synthesis of Titanium Dioxide

Titanium dioxide was synthesized using the direct current thermal plasma jet apparatus of FIG. 1 .

Specifically, a reaction gas inlet was installed in the reaction tube of the thermal plasma jet apparatus at a distance of 2 mm next to the plasma jet nozzle, and carbon dioxide and titanium tetrachloride were injected as a reaction gas in a direction parallel to the plasma jet generation direction. The flow rate of carbon dioxide was controlled using a mass flow controller, and argon gas was used as a carrier gas of vaporized titanium tetrachloride to fix the injection amount of titanium tetrachloride. The carrier gas flow rate was fixed at 2 L / min, and the temperature of the thermostat was maintained at 30 ° C to fix the temperature of titanium tetrachloride. In this case, the DC thermal plasma jet device used a direct current, a voltage of 40V, a current of 150A, and argon gas was used as a thermal plasma generating gas.

In the reaction tube, argon gas is flowed between the anode nozzle and the cathode rod of the torch unit to generate a plasma jet, and the carbon dioxide and titanium tetrachloride are decomposed using the plasma, and then moved to a cooling tube to supply cooling water around the cooling tube. By quenching, nanosized titanium dioxide was synthesized. After the reaction, the gas passed through the scrubber, and then confirmed the decomposition rate of carbon dioxide through gas chromatography.

<Analysis>

After observing the synthesized titanium dioxide nanoparticles by using a scanning electron microscope, the results are shown in Fig.

As shown in FIG . 3 , it was confirmed that the produced particles were well dispersed in a spherical shape and had an average particle diameter of 30 to 40 nm.

Further, after the titanium dioxide nanoparticles by X-ray diffraction analysis, the results are shown in Fig.

As shown in FIG . 4 , it was confirmed that the synthesized titanium dioxide nanoparticles mostly had an anatase phase.

Furthermore, the specific surface area of the titanium dioxide nanoparticles was measured by the BET method.

As a result, the specific surface area of the synthesized titanium dioxide nanoparticles ranged from 78 to 81 m ² / g. From this, it can be seen that the titanium dioxide nanoparticles prepared according to the present invention can have high efficiency in view of catalytic properties by having a large specific surface area.

< Experimental Example > Decomposition rate of carbon dioxide according to the flow rate of carbon dioxide

After the synthesis of titanium dioxide nanoparticles while changing the flow rate of carbon dioxide to 1 ~ 4L / min, the decomposition rate of carbon dioxide was measured using gas chromatography through the discharged gas.

In addition, the decomposition rate of carbon dioxide when only carbon dioxide was injected into the reaction gas and carbon dioxide and titanium tetrachloride were also measured.

The measurement results are shown in FIG. 2 and Table 1.

Carbon dioxide
Flow rate (L / min) CO2 decomposition rate (%) carbon dioxide Carbon dioxide + titanium tetrachloride One 90 95 2 81 87 3 76 84 4 67 72

As shown in FIG . 2 and Table 1, it can be seen that the decomposition rate decreases as the flow rate of carbon dioxide increases, and when the carbon dioxide and titanium tetrachloride are injected together, the decomposition rate of carbon dioxide increases by 5.5 to 9%. I can see that.

1 is a perspective view showing an apparatus used for the production of titanium dioxide according to an embodiment of the present invention.

2 is a graph showing the decomposition rate of carbon dioxide according to the flow rate of carbon dioxide using the thermal plasma according to an embodiment of the present invention.

Figure 3 is a scanning micrograph of the titanium dioxide nanoparticles synthesized in accordance with an embodiment of the present invention.

4 is an X-ray diffraction graph of titanium dioxide nanoparticles synthesized according to an embodiment of the present invention.

<Short description of drawing symbols>

1: torch part 2: reaction tube

3: cooling tube 4: exhaust

5: power supply 41: scrubber

42: gas chromatography 43: aspirator

Claims (9)

Injecting carbon dioxide and vaporized titanium tetrachloride as a reaction gas into a reaction tube of a thermal plasma jet apparatus (step 1); Decomposing the injected carbon dioxide into a thermal plasma jet generated using argon gas to react with titanium tetrachloride carried by the carrier gas (step 2); And Method for producing titanium dioxide nanoparticles using thermal plasma comprising the step (step 3) of cooling the produced titanium dioxide nanoparticles. The method of claim 1, wherein the carbon dioxide and titanium tetrachloride are injected to a position within 2 mm from the plasma jet nozzle in a direction parallel to the plasma jet generation direction. The method of claim 1, wherein argon gas is used as a carrier gas to maintain a constant injection amount of titanium tetrachloride, and the temperature of the thermostat is maintained at 30 to 35 ° C. of the titanium dioxide nanoparticles using thermal plasma. Manufacturing method. The method of claim 1, wherein the cooling of the step 3 is a method of producing nanoparticles of titanium dioxide using thermal plasma, characterized in that using a water cooling method of quenching with cooling water of 15 to 25 ℃. The method of claim 1, wherein the production method of titanium dioxide nanoparticles using thermal plasma, characterized in that for adjusting the flow rate of carbon dioxide in the range of 1 ~ 3L / min to improve the decomposition rate of carbon dioxide decomposed by thermal plasma Manufacturing method. Titanium dioxide nanoparticles prepared by the method of claim 1. The titanium dioxide nanoparticles of claim 6, wherein the titanium dioxide nanoparticles have an average particle diameter of 20 to 50 nm. The titanium dioxide nanoparticles according to claim 6, wherein the titanium dioxide nanoparticles have an anatase phase. The titanium dioxide nanoparticles according to claim 6, wherein the titanium dioxide nanoparticles have a large specific surface area of 78 to 81 m ² / g.

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