KR20010069372A - The manufacturing method of titanium oxide photocatalyst by CVD - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a titanium oxide photocatalyst using the Chemical Vapor Deposition (CVD) method, comprising a titanium oxide film having anatase type crystals with a low content of impurities and a large specific surface area. It is an object of the present invention to provide a method for producing a titanium oxide photocatalyst using a chemical vapor deposition method that is formed on the surface of the substrate to maximize the photocatalyst properties. To achieve the above object, the present invention provides a heating furnace by volatilizing an organic titanium compound. In the process of decomposing at high temperature to form a titanium oxide film on the surface of the substrate by transporting to the reactor in the reactor, the organic titanium compound evaporated separately through the bypass line before reaching the set reaction condition of the reactor and lowering the temperature during the reaction is completed. Trapping and return to the reactor only when the set reaction conditions are reached. It can achieve by providing the manufacturing method of a titanium oxide photocatalyst using the chemical vapor deposition method characterized by sending.

Description

The manufacturing method of titanium oxide photocatalyst by CVD}

The present invention relates to a method for producing a titanium oxide photocatalyst by using a chemical vapor deposition (CVD) method, and more specifically, impurities by forming a titanium oxide film on the photocatalyst substrate by CVD. The present invention relates to a method for producing a titanium oxide photocatalyst using a chemical vapor deposition method in which the anatase type crystal having a small content and a large specific surface area has a large crystal surface, thereby maximizing photocatalytic properties.

Generally, titanium oxide (TiO ₂ ) has a bandgap energy (Eg) corresponding to about 3.0 eV, and when excited with light having a wavelength above the bandgap, electrons in the valence band are excited as conduction bands. Holes are formed in the film and move to the surface of the photocatalyst layer. At this time, when the hole or the water or OH group on the surface of the photocatalytic layer reacts, OH radicals having strong oxidizing power are produced. It is well known that this OH radical exhibits bactericidal properties by decomposing organic substances adsorbed on the surface into harmless compounds or by oxidizing pathogens.

Due to the above characteristics, studies using titanium oxide photocatalysts are being actively conducted. In general, the photolysis reaction occurs on the surface of the photocatalyst. When a predetermined amount of titanium oxide is in contact with the decomposition material, the photolysis reaction is inhibited and the purification ability is lowered. Therefore, coating the titanium oxide of the fine particles on the porous carrier to improve the photolysis characteristics is recommended. It is desperately required. In particular, in the case of titanium oxide, the crystal structure is anatase (anatase) phase, when the fine particles and the specific surface area is excellent in the photocatalyst properties, many photocatalyst manufacturing methods for satisfying these properties are being studied.

Various methods are known as the photocatalyst manufacturing method, that is, a method of fixing the titanium oxide powder to a substrate.

First, a method of mixing titanium oxide powder in an adhesive or a binder and applying it to a substrate to fix it is known. However, this method is simple, but the surface area of titanium oxide which exhibits catalytic reaction activity by adhesive or binder decreases, and the performance decreases, and the adhesive or binder is deteriorated by the strong oxidant produced by the photocatalytic action of titanium oxide. The catalyst is damaged as it is desorbed.

Second, a method of oxidizing a surface of a substrate to titanium oxide by heating or anodizing metal titanium in air is known. However, this method is disadvantageous in that the price of metal titanium is expensive and a large specific surface area cannot be obtained.

Third, a method is known in which a sol obtained by hydrolyzing a metal alkoxide compound is applied to a substrate and calcined. This method is the most widely used method. However, the resolving phenomenon of electrons and holes, which contain acid or organic substances in the sol, cannot obtain pure titanium oxide film, and the resultant titanium oxide has many crystal defects and degrades catalytic activity. This has a problem that arises.

Separately, a CVD method is known in which a metal oxide film or halide is volatilized in a semiconductor manufacturing process and decomposed in a heating furnace to form a titanium oxide film on a substrate. However, in this case, since the organometallic compound or halide cannot be completely decomposed after the initial reaction and the reaction, a titanium oxide film containing a large amount of organic material is formed on the surface of the substrate, making it difficult to use as a photocatalyst, and crystals having a small specific surface area are precipitated. There is a disadvantage that the activity is reduced.

Accordingly, the present inventors have completed the present invention by studying a method of forming a titanium oxide film of high purity on a substrate using the CVD method and simultaneously forming a titanium oxide film having a large specific surface area and excellent photocatalytic properties.

Accordingly, an object of the present invention is to provide a method for producing a titanium oxide photocatalyst using a chemical vapor deposition method in which a titanium oxide film having a small amount of impurities and a specific surface area of anatase type crystals can be formed on a substrate for photocatalyst by CVD technique. To provide.

1 is a view schematically showing a device of the manufacturing process of the titanium oxide photocatalyst using the chemical vapor deposition method according to the present invention.

Figure 2 shows the results of the FT-IR analysis of the titanium oxide film formed according to the temperature change.

Figure 3 is a view showing the X-ray diffraction analysis of the titanium oxide film formed according to the temperature change.

4 is a view showing the absorbance of methylene blue over time for comparing the properties of the photocatalyst prepared according to the temperature change.

5 is a view showing the absorbance of methylene blue over time for the comparison of the properties of the photocatalyst according to the present invention and the photocatalyst prepared by the conventional sol-gel method.

<Explanation of symbols for the main parts of the drawings>

1: evaporator 2: electric furnace 3: reactor

4: temperature sensor 5: bypass line

The present invention to achieve the above object

In the method for producing a titanium oxide photocatalyst using a chemical vapor deposition method in which the organic titanium compound is volatilized, transferred to a reactor in a heating furnace, decomposed at high temperature to form a titanium oxide film on the surface of the substrate, and the organic titanium compound is reacted with a predetermined reaction condition of the reactor. Before the reaction is completed and the reaction is completed and the temperature is lowered during the period of trapping separately through the bypass line, the method of producing a titanium oxide photocatalyst using the chemical vapor deposition method characterized in that the transfer to the reactor only when the set reaction conditions of the reactor is reached. It can be achieved by providing a.

In addition, in the present invention, 20% to 50% of the oxidant gas is included with respect to the total flow rate flowing into the reactor, and the film forming temperature is 300 ° C to 500 ° C. Provide a method.

Hereinafter, a method of preparing a titanium oxide photocatalyst using a chemical vapor deposition method will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the present invention. .

1 is a view schematically showing the configuration of the manufacturing process of the titanium oxide photocatalyst using the chemical vapor deposition method according to the present invention, with reference to the drawings the manufacturing configuration of the titanium oxide photocatalyst using the chemical vapor deposition method according to the present invention Looking at it, the evaporator (1) for receiving an organic titanium compound; A reactor (3) formed in an external heating type electric furnace (2) for decomposing the organic titanium compound at a high temperature to form a titanium oxide film on a substrate; An argon gas supply pipe formed to transfer the organic titanium compound evaporated in the evaporator 1 to the reactor 3; Oxygen supply pipe for oxidation of raw materials; And a bypass line for separately trapping the organic titanium compound evaporated before reaching the reaction condition set in the process of volatilizing the organic titanium compound and transferring to the reactor 3 and during the period of lowering the temperature after the reaction is completed ( 5) and nitrogen trap and vacuum pump. In the drawing, reference numeral 4 denotes a temperature sensor.

In order to form a titanium oxide film on a substrate in the device having the above configuration, the present invention first heats and evaporates the organic titanium compound contained in the evaporator 1, and the evaporated compound is a carrier gas by argon gas (3). Is transferred to). The organic titanium compound transferred to the reactor 3 is decomposed at a high temperature in the reactor 3 to form a titanium oxide film on the surface of the substrate placed in the reaction vessel.

In this case, various types of organic titanium compounds may be used as the organic titanium compound, but in the present invention, titanium isopropylate (Ti [OCH (CH3) ₂ ] ₄ ) was used, and the bubbler evaporator (1) Was supplied to the reactor (3). At this time, argon gas was used as a carrier gas for supplying the evaporated titanium tetraisopropylate to the reactor (3).

The titanium tetraisopropylate transferred to the reactor 3 is decomposed by the high temperature in the reactor 3 to form a titanium film on the surface of the substrate, wherein the reaction conditions in the reactor 3 have a total flow rate of 500 sccm to 1500 sccm, The pressure was 10 tortor to 100torr and the film formation temperature was 200 to 500C.

In the above, the flow rate and the pressure were determined in a conventional range, wherein the film formation temperature was performed in the range of 250 ° C to 500 ° C. When the film is formed within the temperature range, the crystal of the titanium oxide film formed on the surface of the substrate has an anatase crystal. In this case, when the film formation temperature is less than 250 ° C., an amorphous titanium oxide film is synthesized. When the temperature exceeds 500 ° C., a titanium oxide film having a rutile structure is synthesized. Therefore, it is preferable to form a film at a temperature within the above range. In the present invention, oxygen gas as an oxidant was injected into the reactor 3 at 20% to 50% of the total supply gas flow rate in order to promote oxidation of the organotitanium compound. In other words, when oxygen is supplied, it is possible to form a homogeneous titanium oxide film by promoting the oxidation of titanium when the titanium oxide film is formed. At this time, if the supply flow rate of oxygen gas is less than 20% of the total flow rate, crystals with oxygen defects are formed when TiO ₂ is formed, and catalyst activity is lowered. Particles are formed by the reaction, which lowers the film formation, so it is preferable to supply oxygen within the above range.

Under such pressure, titanium tetraisopropylate is evaporated at 30 ° C. to 50 ° C. and is sent to the reactor 3, where the titanium tetraisopropylate is evaporated and transferred to the reactor 3 as the temperature increases. At this time, the titanium tetraisopropylate transferred before the temperature of the reactor 3 reaches the set temperature condition is not completely decomposed, thereby forming a titanium oxide film containing an organic material on the surface of the substrate. Therefore, there is a problem that the catalytic activity of the prepared photocatalyst is lowered by not forming a pure titanium oxide film. In addition, after the reaction is completed, the titanium tetraisopropylate supplied in the process of lowering the temperature of the reactor 3 is not completely decomposed to form an incomplete titanium oxide film. That is, since titanium tetraisopropylate is not sufficiently decomposed, a titanium oxide film containing an organic material is formed, which causes a problem of lowering catalytic activity. Accordingly, in the present invention, in order to solve the above problems, the titanium tetraisopropylate is volatilized and transferred to the reactor 3 before the reaction condition set by the reactor 3 is reached and the reaction is completed to lower the temperature. The titanium tetraisopropylate was trapped using a bypass line 5 and a nitrogen trap formed separately during the period.

In addition, in the present invention, the organic titanium compound was decomposed at high temperature in the reactor (3) to filter particles formed in the process of forming a titanium oxide film on the surface of the substrate was filtered with a membrane filter of 10㎛ size.

When the titanium oxide film is manufactured by chemical vapor deposition as described above, a pure titanium oxide film free of impurities can be prepared, and excellent titanium oxide crystals free of crystal defects can be prepared to produce a titanium oxide photocatalyst having excellent photocatalytic performance. can do. In particular, using the chemical vapor deposition method can not only form a large area of the titanium oxide film with a small amount of raw material, but also can produce a titanium oxide film in a short time, it is possible to produce a titanium oxide film excellent in adhesion with the substrate. In addition, there is an advantage that a separate heat treatment process is not required after film production.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are only presented to aid the understanding of the present invention, but the present invention is not limited thereto.

<Example 1>

Using the apparatus shown in Fig. 1, alumina balls having a diameter of 8 mm were mounted in a reactor 3 formed in an externally heated electric furnace 2, and the temperature in the reactor 3 was maintained at 200 deg. The evaporator 1 containing the rate is slowly heated to maintain 40 ± 10 ° C., and the evaporated titanium isopropylate is transferred to the reactor 3 using argon gas to form a titanium oxide film on the alumina ball surface to form a photocatalyst. Prepared. At this time, the titanium tetraisopropylate was trapped using a bypass line 5 and a nitrogen trap formed separately before the reaction condition set by the reactor 3 and the reaction was completed to lower the temperature. Titanium tetraisopropylate was fed when the reactor 3 reached the set reaction conditions. The flow rate in the reactor 3 at this time was 1000 sccm (argon gas: oxygen gas 7: 3), and the pressure was fixed at 10 torr.

<Example 2>

The photocatalyst was prepared in the same manner as in Example 1 except that a titanium oxide film was formed on the surface of the alumina ball at a temperature of 500 ° C. in the reactor 3.

<Example 3>

The photocatalyst was prepared in the same manner as in Example 1 except that a titanium oxide film was formed on the surface of the alumina ball at a temperature of 800 ° C. in the reactor 3.

Experimental Example 1

In order to confirm whether the organic material is contained in the titanium oxide thin film on the surface of the alumina balls of the photocatalysts prepared in Examples 1 to 3, the results were shown by FT-IR.

As shown in FIG. 2, all of the titanium oxide films prepared in Examples 1 to 3 did not have organic peaks observed in all regions, and the peak observed at about 2380 cm −1 was a CO 2 peak. Therefore, it can be seen that all the titanium oxide films prepared using the experimental apparatus, that is, the bypass line, are pure titanium oxide films of high quality without organic substances remaining.

Experimental Example 2

CuKα, Ni filter, 30kV, 20mA using an X-ray diffraction analyzer (Philips. Co. Pw1720, Holland) to check the titanium oxide crystal structure formed on the surface of the alumina ball of the photocatalyst prepared in Examples 1 to 3 It measured on condition and the result is shown in FIG.

As shown in FIG. 3, in the case of Example 2, in which the temperature in the reactor was set at 200 ° C., which is less than the range of the present invention, it can be seen that the titanium oxide crystals exhibited an amorphous phase. In Example 2 it can be seen that anatase type crystals were formed. In addition, in the case of Example 3 performed at a temperature of 800 ° C., it can be seen that rutile crystals were formed.

Experimental Example 3

In order to examine the characteristics of the photocatalysts prepared in Examples 1 to 3, 10 ^-5 mol / l methylene blue solution and the photocatalysts prepared above were filled in a petri dish, respectively, and the absorbance of the solution according to time change was measured. Observation was carried out with an absorbance spectrometer (580 nm), and the results are shown in FIG. 4. In this case, the absorbance of the pure solution (Ref.) Without the photocatalyst is shown together for easy comparison.

As shown in FIG. 4, it can be seen that there is almost no change in absorbance in the case of the pure solution without the photocatalyst, but it can be seen that the change in the absorbance appears when the photocatalyst is used. That is, it can be seen that the methylene blue is decomposed and the absorbance gradually decreases. In particular, it can be seen from FIG. 4 that the photocatalyst of Example 2 according to the present invention has superior characteristics as compared to the photocatalysts prepared in Examples 1 and 3.

Based on Experimental Examples 1 to 3, it can be seen that the photocatalyst of Example 2 prepared within the preferred temperature range of the present invention has the highest catalytic activity.

Experimental Example 4

In order to compare the photocatalytic properties of the photocatalyst prepared in Example 2 with the photocatalyst prepared by the conventional sol-gel method, 10 ^-5 mol / l methylene blue solution and the photocatalyst prepared by the photocatalyst and sol-gel method of Example 2 were petri dishes. Filled in a petri dish to observe the absorbance of the solution according to time change with an absorbance photometer (360 nm), and the results are shown in FIG. 5. In this case, the photocatalyst by the sol-gel method is prepared by mixing titanium tetraisopropoxide with water and nitric acid to prepare a titania sol by a conventional method, repeating the alumina ball in the titania sol three times, and then drying and calcining it. A titanium oxide photocatalyst of anatase crystal structure obtained by heat treatment at a temperature of 500 ° C. for 24 hours was used.

As shown in FIG. 5, it can be seen that the absorbance decreases as the reaction time elapses. In particular, the photocatalyst prepared by chemical vapor deposition according to the present invention has a low absorbance at a very fast time compared with the photocatalyst prepared by the sol-gel method. It can be seen that the photocatalyst properties are excellent.

As described above, the present invention uses a CVD technique to form a titanium oxide film having anatase-type crystals with a low impurity content and a large specific surface area using a CVD technique, thereby maximizing photocatalytic properties. It is a useful invention to provide a method for producing a titanium oxide photocatalyst using vapor deposition.

Claims (5)

In the method for producing a titanium oxide photocatalyst using a chemical vapor deposition method of evaporating an organic titanium compound and transporting it to a reactor in a heating furnace to decompose to high temperature to form a titanium oxide film on the surface of the substrate, The organic titanium compound is trapped separately through a bypass line before reaching the set reaction conditions of the reactor and during the period of lowering the temperature, and transported to the reactor only when the set reaction conditions of the reactor are reached. Method for producing titanium oxide photocatalyst using vapor deposition method. The method of claim 1, wherein the organic titanium compound is decomposed under a high temperature in a reactor to filter particles formed in a process of forming a titanium oxide film on the surface of the substrate by filtering with a membrane filter having a size of 10㎛ size. Method for producing titanium oxide photocatalyst by vapor deposition. The method for producing a titanium oxide photocatalyst according to claim 1 or 2, wherein the film forming temperature of the reactor is 300 ° C to 500 ° C. The method of claim 3, wherein the oxidant gas is included in an amount of 20% to 50% with respect to the total flow rate flowing into the reactor. The method for producing a titanium oxide photocatalyst according to claim 4, wherein the organotitanium compound is titanium tetraisopropoxide.