KR20090090585A - Method for decomposing volatile organic compound using novel titanium dioxide catalyst with the increased specific surface - Google Patents

Abstract

A method for decomposing VOC with a titandioxide catalyst is provided to improve light resolution ability per catalyst unit weight by adding a surfactant and offering a wide specific surface area in comparison to existing titanium dioxide. A method for decomposing VOC with a titandioxide catalyst includes a step for contacting a volatile organic matter and a titandioxide catalyst layer(20). The titandioxide catalyst layer includes a support and the titandioxide catalyst of which specific surface area is 100 ~ 300 m^2/g, and fixed on the top of the support. The support is optical fiber(4). A diameter of the optical fiber is 0.5 ~ 5mm. Thickness of the titandioxide catalyst layer is 2 ~ 15mum.

Description

Method for decomposing volatile organic compound using novel titanium dioxide catalyst with the increased specific surface}

The present invention relates to a method of decomposing VOC using a novel titanium dioxide catalyst having an increased specific surface area, and more particularly, to adding a surfactant in preparing a sol-gel method of titanium dioxide, to a conventional titanium dioxide catalyst. The present invention relates to a method of decomposing VOC using a titanium dioxide catalyst having a large specific surface area and high photodegradability per unit weight of the catalyst.

Currently, odor-causing substances are commonly referred to as VOCs (volatile organic matter), and are used for air degassing, hazardous waste incineration facilities, chemical product manufacturing, textile product manufacturing, fertilizer manufacturing facilities, biological wastewater treatment facilities, carbon regeneration facilities, urban landfill sites, and dry It occurs in cleaning facilities, degreasers, freon facilities, and food industry. Volatile organic substances such as toluene, acetone, and methyl ethyl ketone (MEK) emitted from factories cause discomfort and resistance even at low concentrations, causing conflicts and prolonged exposure to high concentrations can cause respiratory failure and carcinogenesis. Becomes The expansion of residential areas reduces the gap with factories, so the management of odor-causing substances is essential, and the efficient removal of volatile organics, which are inevitably released during the operation phase, is very important for producers in terms of reducing the environmental cost burden.

Methods used for removing volatile organics include adsorption, combustion, air dilution, and via filter. Adsorption methods are economically inexpensive and simple to use, but they are used a lot. However, the efficiency of the adsorbent drops within a short period of time. The combustion method has the advantage of simple removal process and easy management, but there is a possibility of harmful secondary by-products caused by rising power costs and combustion. The air dilution method is easy to use, but if it is applied in the long term, it may cause serious environmental problems. As the environmental regulations are strengthened, the benefits of using the air diminish gradually. The buyer filter method is limited in the target material and difficult to process at high concentration and high speed.

In order to solve these problems, techniques for removing organic materials using photochemical catalysts have been examined, and there are the following prior arts.

The photocatalyst research was mainly performed for the slurry type reaction (Korean Patent No. 0185179) in which powder photocatalyst was mixed with a reactant. However, the photocatalyst was limited in practical use due to problems such as deterioration of stability of solution due to precipitation of powder. Thereafter, there are two types of application of the photocatalyst solution. First is a dispersion using a photocatalyst powder. The film coated with this dispersion has the advantage of excellent photocatalyst performance such as crystallinity of particles and adsorption of organic matter, decomposition and hydrophilicity. However, since the transparency of the coating film and its adhesion (fixation) are weak, the coating film is easily detached even in a small impact, and thus many problems have appeared in practical use. Therefore, a method of immobilization using a binder using a silicon compound or the like has been mainly studied, but there is a problem in that the photocatalytic activity is lowered. For example, U.S. Patent No. 5,755,867 on photocatalytic immobilization using an adhesive improves adhesion by using a method of preparing a binder using a silicon compound and dispersing titanium oxide thereon to coat the substrate. There was a problem. Second, after preparing a coating solution by a sol-gel (Sol-Gel) process using a metal alkoxide as a starting material instead of a dispersion is to form a coating film using this. The solution according to the Sol-Gel process can prepare a solution having small particles (<10 nm), thereby obtaining excellent transparency by forming a coating film, and by including an excess of acid in stoichiometric amounts in the preparation By further increasing the bonding density, there is an advantage that the density or hardness of the coating film can be increased through heat treatment at room temperature or low temperature. However, the photocatalyst prepared by the general sol-gel method has a disadvantage in that the catalytic activity decreases because the specific surface area is only about 50 m 2 / g.

Meanwhile, related technologies for removing VOCs are as follows. In Korean Patent No. 0324541, a VOC such as trichloroethylene (TCE) was removed using a tubular photochemical reactor filled with a photocatalyst-coated filler. The patent is a system of a photochemical reaction apparatus which coats a conventional titanium dioxide catalyst on the packed bed surface and decomposes the organic material in contact with the packed bed. Korean Patent No. 0469005 describes a technique for enhancing photolysis efficiency by attaching a VOC to a reactor inner wall using a photoreactor having a photocatalyst sol-coated carrier attached on a metal plate. The patent is similar to the technical elements of the packed layer of Korean Patent No. 0324541 in that the VOC is removed by using a photocatalyst coated carrier. In addition, in Korean Patent No. 0714849, titanium dioxide was fixed in a reactor using silane to remove VOC. When silane is used as a binder to fix titanium dioxide, the adhesion is excellent, but if it is subjected to high heat for a long time, the silane may be transformed into a material having a double bond and ultimately decreases the photolysis efficiency of titanium dioxide.

Therefore, there is a need for a highly active photocatalyst capable of efficiently removing volatile organic substances generated in industrial sites that are distinguished from the prior art.

An object of the present invention is to solve the problems of the prior art as described above, and to provide a method for decomposing volatile organic matter (VOC) using a titanium dioxide photocatalyst having an increased specific surface area.

In order to achieve the above object, the present invention

A method of decomposing a volatile organic substance (VOC), comprising contacting a volatile organic substance (VOC) with a support layer and a titanium dioxide catalyst layer fixed on the support and containing a titanium dioxide catalyst having a specific surface area of 100 to 300 m ² / g. To provide.

The titanium dioxide catalyst according to the present invention has fine surface pores, and thus has a high surface resolution per unit weight of the catalyst since the specific surface area is more than twice as wide as that of the existing titanium dioxide.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated concretely.

The present invention

A method of decomposing a volatile organic substance (VOC), comprising contacting a volatile organic substance (VOC) with a support layer and a titanium dioxide catalyst layer fixed on the support and containing a titanium dioxide catalyst having a specific surface area of 100 to 300 m ² / g. It is about.

The titanium dioxide catalyst has a specific surface area of 100 to 300 m ² / g, more preferably 120 to 300 m ² / g, most preferably 150 to 300 m ² / g. If the specific surface area of the titanium dioxide catalyst is less than 100 m 2 / g, the treatment efficiency of harmful substances is lowered. If it exceeds 300 m 2 / g, the synthesis of the titanium dioxide catalyst may be difficult.

The type of the support is not particularly limited, and includes glass, metal plates, ceramic plates, various polymers or optical fibers. In particular, an optical fiber is preferable in view of efficient use of light. The type of optical fiber is not particularly limited, but a glass-based optical fiber or a plastic-based optical fiber may be used, but considering the sintering temperature, it is preferable to use an optical fiber made of quartz.

The diameter of the optical fiber is not particularly limited, but is preferably 0.5 to 5 mm. When the diameter of the optical fiber is less than 0.5mm, it is difficult to maintain the durability of the photocatalyst layer, and when the diameter of the optical fiber exceeds 5mm, partial light source deviation occurs, so that it is difficult to maintain constant photo resolution.

The fixed titanium dioxide catalyst layer preferably has a thickness of 2 to 15 µm, more preferably 5 to 10 µm. If the thickness is less than 2 μm, the light resolution is lowered. If the thickness is more than 15 μm, the light resolution may be lost (absorption, reflection, etc.), thereby degrading the light resolution.

Titanium dioxide catalyst according to the present invention

A first step of reacting by adding titanium alkoxide to a mixture of a solvent and a surfactant;

A second step of fixing the reactant to a support;

Extracting a surfactant from the reactant immobilized on the support; And

The surfactant may be prepared by a fourth step of sintering the extracted reactant.

The first step is to synthesize titanium dioxide by the sol-gel method. The solvent of the first step is preferably used one or more selected from the group consisting of water, alcohol, and cellosolve. Methanol, ethanol, propanol, butanol, isopropanol, or diacetyl alcohol may be used as the alcohol, and methyl cellosolve, ethyl cellosolve, butyl cellosolve, or cellosolve acetate may be used as the cellosolve. Can be.

In addition, the surfactant is preferably at least one selected from the group consisting of alkylhaloids, alkylamines, and alkylphosphates. As for carbon number of the surfactant which has the said alkyl group, it is more preferable that it is 10-20. If the carbon number of the alkyl is less than 10, the specific surface area improvement effect is inferior, and if it exceeds 20, it is difficult to control the shape and size of the pores.

The alkyl-based surfactant is preferably contained in 2 to 25 parts by weight, more preferably 3 to 23 parts by weight, most preferably 5 to 20 parts by weight based on 100 parts by weight of the organic solvent. If the content is less than 2 parts by weight, the pore-forming effect is lowered, and if it exceeds 20 parts by weight, the shape and size uniformity of the pores is inferior.

The titanium alkoxide is preferably a compound represented by the following formula (1).

Ti (OR) ₄

In the formula, R represents an alkyl group having 1 to 6 carbon atoms.

The titanium alkoxide includes titanium propoxide (titanium (IV) propoxide), titanium isopropoxide (titanium (IV) isopropoxide), titanium diisopropoxide (titanium (IV) diisopropoxide) and titanium butoxide (IV titanium (IV) ) butoxide), titanium ethoxide (Titanium (IV) ethooxide), and titanium methoxide (Titanium (IV) methoopoxide) may be used.

The titanium alkoxide is preferably included in 1 to 10 parts by weight based on 100 parts by weight of the organic solvent. If the content is less than 1 part by weight, the photolysis effect is lowered. If the content is more than 10 parts by weight, the photocatalyst concentration may be too high, thereby reducing the photolysis effect due to light loss.

In addition, the solvent of the first step may further use an inorganic binder for fixing the photocatalyst.

The inorganic binder may be a titanium-based inorganic binder such as titanium tetraisopropoxide, titanium tetraethoxide, titanium tetrapropoxide, or titanium tetrabutoxide, zirconium tetraethoxide, zirconium tetrapropoxide, or zirconium tetra Zirconium-based inorganic binders such as butoxide, aluminum tetraethoxide, aluminum tetrapropoxide, aluminum-based inorganic binders such as aluminum tetrabutoxide, or tungsten-based inorganic binders such as tungsten hexaethoxide alone or two kinds It can use above, It is preferable to use a titanium type inorganic binder especially.

The inorganic binder is preferably added in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the organic solvent. If the content of the inorganic binder is less than 0.01 parts by weight, the photocatalyst may fall due to the external environment, and if it exceeds 0.5 parts by weight, the photocatalytic effect of the photocatalyst may be lowered.

Meanwhile, the solvent of the first step may use an acid or a base catalyst for controlling pH and reaction rate, and for storage stability and dispersibility of an anatase type titanium dioxide sol. The acid or base catalyst may be used alone depending on the storage stability and physical properties of the photocatalyst sol, or two or more catalysts may be used in combination. Acid catalysts include acetic acid, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, chlorosulphonic acid, para-toluenesulphonic acid, trichloroacetic acid, polyphosphoric acid, iodixic acid, or iodic anhydride perchloric acid, and the like. Base catalysts include caustic soda, potassium hydroxide, normal butylamine, imidazole, ammonium perchlorate and the like.

The first step is preferably performed as follows, but is not particularly limited thereto.

1 part by weight to 10 parts by weight of Ti (OR) ₄ (wherein R represents an alkyl group having 1 to 6 carbon atoms) and 2 to 25 parts by weight of an alkyl-based surfactant, followed by stirring for 0.5 to 1.5 hours. , TTIP (titanium tetraisopropoxide) is added to 0.01 to 0.5 parts by weight and reacted with sufficient stirring for 0.2 to 1 hour.

In the method for producing titanium dioxide according to the present invention, the second step is to fix the reactant prepared in the above step to the support.

The method of fixing the reactant prepared from the first step to the support is not particularly limited, but is preferably fixed according to the wet coating method. More preferably, the wet coating method is a dip coating method in which the photocatalyst is applied to the surface of the support by being put in a liquid state.

In addition, the reactant fixed by the dip coating is preferably dried at room temperature for 1 hour or more.

In the method for producing titanium dioxide according to the present invention, the third step is to extract the surfactant from the immobilized reactant.

It is preferable to use the inorganic acid aqueous solution or the supercritical extraction method for the extraction of the surfactant.

In the case of using an aqueous inorganic acid solution, the surfactant may be extracted by precipitating the reactant fixed to the support in the aqueous inorganic acid solution. The inorganic acid aqueous solution includes hydrochloric acid, nitric acid, sulfuric acid, and the like. The concentration of the inorganic acid aqueous solution is not particularly limited, but is preferably 1 to 20 ml / L. If the concentration is less than 1 ml / L, the extraction amount of the surfactant may be small, and the specific surface area of the titanium dioxide catalyst may be lowered. If the concentration is more than 20 ml / L, the extraction capacity may be constant even under conditions above the concentration, and only the production cost may be increased. In addition, the extraction time is not particularly limited, but is preferably precipitated for 3 to 5 hours.

In addition, when the supercritical extraction is used, the carbon dioxide supercritical fluid is mainly used, and it is preferable to proceed for 10 to 60 minutes at a pressure of 8 to 15 MPa and a temperature of 30 to 50 ° C.

In the method for producing titanium dioxide according to the present invention, the fourth step is to sinter the photocatalyst having pores to form a photocatalyst layer.

The catalyst in which the pores are formed is preferably sintered at 80 ° C. to 110 ° C. for 30 minutes to 2 hours, and then secondarily sintered at 400 ° C. to 700 ° C. for 30 minutes to 2 hours to obtain a photocatalyst having crystalline characteristics.

In the decomposition method of VOC according to the present invention, the decomposition apparatus of VOC is not particularly limited, but it is preferable to use the photolysis apparatus shown in FIG.

The photolysis device comprises a reaction unit (5) equipped with one or more optical fibers (4) on which a photocatalyst layer (20) is formed; An ultraviolet light supply unit 1 for transmitting the ultraviolet light to the optical fiber of the reaction unit; And a mixing unit 6 for supplying contaminants and moisture to the reaction unit 5, wherein the photocatalytic layer 20 includes the titanium dioxide photocatalyst of the present invention having a specific surface area of 100 to 300 m ² / g. .

In more detail with reference to FIG. 1, the ultraviolet light collected by the ultraviolet light supply unit 1 is transmitted into the reaction unit 5 through the optical fiber 4.

The reaction unit 5 is preferably a hollow tube member capable of installing a plurality of optical fibers 4, but the shape thereof is not necessarily limited thereto, and the characteristics of the target material, initial and discharge supply concentrations, treatment costs, and the like. Subject to change.

In the optical fiber 4 constituting the reaction unit 5, the photocatalyst 20 is fixed to the surface from which the coating is removed.

The ultraviolet light supply unit 1 is composed of an artificial lamp 2 and a condenser 3 that emit ultraviolet light, and the ultraviolet light emitted from the lamp 2 is condensed by the condenser 3 and transmitted to the optical fiber. The artificial lamp is not particularly limited, but a BLB lamp (6 W, 365 nm wavelength) may be used to increase the photo resolution of titanium dioxide or a photocatalyst having a bandgap energy of 3.0 eV or less. In order to increase the light collecting efficiency of the light collector, a concave lens is attached. Preferably, a reflection plate is installed on the inner wall of the ultraviolet light supply unit to minimize the loss of the light source. In case of connecting tube in contact with optical fiber in UV supply unit, it may be heated with long term use.

In the photolysis apparatus, water is supplied from a water supply unit 100, and the water supply unit 100 includes an air compressor 9, a flow meter 8, and a moisture generator 7. Air supplied from the air compressor 9 is introduced into the moisture generator 7 at a constant flow rate through the flow meter 8 and then supplied to the mixing unit 6 in a state of being mixed with a predetermined amount of water.

In the mixing unit 6, harmful substances, air and moisture supplied from the external device 10 are constantly stirred, and then supplied into the reaction unit 5 through the inlet 11. The purification material produced by the catalytic reaction in the reaction unit 5 is discharged to the outside through the outlet 12.

In addition, the titanium dioxide photocatalyst of the present invention, which is fixed to the photolysis device, generates high-oxidation hydroxyl radical (· OH) capable of receiving energy from ultraviolet light and decomposing organic matter, based on a mixed gas supplied to the reaction unit 25 to 55. At vol% moisture, this reaction is more active. In the condition below 25 vol%, the photodegradation is not only degraded, but only the outer chain (methyl group, etc.) is decomposed while maintaining the cyclo structure of the volatile organic matter, and when it is supplied in excess of 55 vol%, water droplet agglomeration occurs inside the reactor. Brings loss.

Hereinafter, the above-described invention will be described in detail based on the following examples. However, the following examples are only for illustrating the present invention, and the present invention is not limited thereto. Analysis of the samples prepared in Examples and Comparative Examples of the present invention was performed by the following method.

(1) photo resolution

Photodegradation was tested by measuring the concentration of organics present in the gas using gas chromatography-mass spectrometry and UV / VIS spectroscopy. The GC-mass spectrometer used HP-6890 from Hewlett-Packard, USA and the UV-VIS spectrometer used UV-160A from Shimadzu, Japan. Photo resolution was calculated according to the following equation (1).

Resolution (%) = concentration of organic compound removed / concentration of initial organic compound

(2) Specific surface area of photocatalyst

Specific surface area of titanium dioxide was used SA3100 Plus of Beckman Coulter, USA, and the sample was measured after fixing for 40 minutes at 200 ℃.

(3) thickness of the photocatalyst layer

The thickness of the photocatalyst film fixed to the glass tube surface was measured by scanning electron microscopy (SEM), XL30 ESEM-FEG, FEI Co., N.Y., U.S.A.

Example 1 Preparation and Fixation of Titanium Dioxide Catalyst with Increased Specific Surface Area

100 parts of alcohol was mixed with 8 parts by weight of nonadecaamine (C ₁₉ H ₄₁ N, KK, Japan, molecular weight 283.54) consisting of 3 parts by weight of Ti (OC ₄ H ₉ ) ₄ and 19 carbon atoms, followed by stirring for 60 minutes. Next, 0.1 parts by weight of TTIP (titanium tetraisopropoxide) was added and reacted with sufficient stirring for 0.5 hour.

The reactants were fixed by dip coating on a 1.5 mm diameter optical fiber made of quartz, dried at room temperature for 2 hours, and the dried photocatalyst was precipitated in 9 mL / L aqueous nitric acid solution for 4 hours to produce nonadecaamine. The components of were sufficiently extracted to form pores. The photocatalyst in which the pores were formed was first sintered at 100 ° C. for 1 hour, and then sintered at 600 ° C. for 1 hour to have crystallinity of titanium dioxide (TiO ₂ ).

At this time, the specific surface area of titanium dioxide was 175 m 2 / g and the thickness of the fixed layer was 6.9 μm.

Experimental Example 1 Degradation Test of Hazardous Substances Using the Photocatalyst of Example 1

The photolysis test of gaseous acetone was performed using the photolysis apparatus shown in FIG. 1. In FIG. 1, the reaction unit 5 uses a cylindrical reactor having a diameter of 50 mm and a length of 1 m, in which 15 titanium dioxide-fixed optical fibers manufactured in Example 1 are embedded, and the UV supply unit 1 As a light source, BLB lamp (6W, dominant wavelength 365nm) was used. Based on the mixed gas supplied through the mixing unit 6, a mixed gas consisting of 30 vol% of water and 100 ppm of acetone is supplied to the reaction unit 5 at a flow rate of 300 mL / sec, and acetone of the off-gas collected after 30 seconds of residence time. The concentration of was 0.5 ppm.

Example 2 Preparation and Fixation of Titanium Dioxide with Increased Specific Surface Area

3 parts by weight of Ti (OC ₄ H ₉ ) ₄ 3 parts by weight of alcohol and 4 parts by weight of nonadecaamine (C ₁₉ H ₄₁ N, KK, Japan, molecular weight 283.54) were mixed and stirred for 60 minutes. Next, 0.1 parts by weight of TTIP was added and reacted with sufficient stirring for 0.5 hour.

The reactants were fixed by dip coating on an optical fiber having a diameter of 1.5 mm made of quartz and then dried at room temperature for 2 hours. The dried photocatalyst was precipitated in 12 mL / L aqueous nitric acid solution for 4 hours to sufficiently extract the components of nonadecaamine to form pores. The photocatalyst in which the pores were formed was first sintered at 95 ° C. for 1 hour, and then sintered at 500 ° C. for 1 hour to have crystallinity of titanium dioxide (TiO ₂ ).

At this time, the specific surface area of titanium dioxide is 125 m 2 / g and the thickness of the fixed layer is 5.7 μm.

Experimental Example 2 Degradation Test of Hazardous Substances Using the Photocatalyst of Example 2

Photolysis test of gaseous MEK was performed using the photolysis apparatus shown in FIG. 1. In FIG. 1, the reaction unit 5 uses a cylindrical reactor having a diameter of 50 mm and a length of 1 m, in which 15 titanium dioxide-fixed optical fibers manufactured in Example 2 are embedded, and a light source of the ultraviolet light supply unit 1. A silver BLB lamp (6 W, dominant wavelength 365 nm) was used. The concentration of MEK (Methyl Ethyl Ketone) in the off-gas collected after 30 seconds of residence gas was supplied to the reaction unit 5 at a flow rate of 300 mL / sec. Is 0.8 ppm.

<Examples 3 to 5 and Comparative Examples 1 to 5>

Titanium dioxide photocatalyst was prepared according to the composition of Table 1, and gas phase organic photodegradation experiments were conducted in the same manner as in Examples 1 and 2, and the results were compared while changing the experimental conditions as shown in Table 1, respectively.

As shown in Table 1, the titanium dioxide photocatalyst layer prepared according to Examples 1 to 5 exhibited an excellent effect of almost entirely decomposing the target material. In addition, it can be seen that the photodegradation of the catalyst is further increased when an appropriate amount of water is included.

From the above results, it was confirmed that the conditions such as the specific surface area of the titanium dioxide photocatalyst, the thickness of the photocatalyst layer, and the like are variables that affect the removal of volatile organics.

1 is a schematic diagram of a photolysis apparatus including a moisture supply apparatus and forming a titanium dioxide catalyst layer having an increased specific surface area according to an embodiment of the present invention.

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

1: UV supply unit 2: UV light artificial lamp

3: condenser 4: optical fiber

5: reaction unit 6: contaminant and moisture supply mixing unit

7: Moisture generating device 8: Flow meter

9: air compressor 10: external device

11: inlet 12: outlet

20: photocatalyst layer 100: moisture supply unit

Claims (8)

A method of decomposing a volatile organic substance (VOC), comprising contacting a volatile organic substance (VOC) with a support layer and a titanium dioxide catalyst layer fixed on the support and containing a titanium dioxide catalyst having a specific surface area of 100 to 300 m ² / g. . The method of claim 1, The support is a method of decomposing volatile organics (VOC), characterized in that the optical fiber. The method of claim 2, Decomposition method of volatile organic compounds (VOC), characterized in that the diameter of the optical fiber is 0.5 to 5mm. The method of claim 1, The thickness of the titanium dioxide catalyst layer is 2 to 15㎛ characterized in that the decomposition method of volatile organics (VOC). The method of claim 1, A method for decomposing volatile organic matter (VOC), characterized in that the volatile organic matter is photodegraded using ultraviolet light. The method of claim 5, Decomposition method of volatile organic matter (VOC), characterized in that additional water is supplied when the photolysis. The method of claim 6, The method of decomposition of volatile organics (VOC), characterized in that the water is supplied mixed with air. The method of claim 6, Decomposition of volatile organics (VOC), characterized in that the water is 25 to 55 vol%.

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