Composite catalyst comprising carbon body and porous support coating for decomposing perfluorinated compounds

Abstract

The present invention relates to a composite catalyst for decomposing perfluorinated compounds, the composite catalyst comprising: a carbon body; and a porous support coating the surface of the carbon body, wherein the porous support comprises porous alumina.

Description

Composite catalyst for decomposing perfluorinated compounds comprising a carbon body and a porous support coating layer

[0001] The present invention relates to a composite catalyst for decomposing perfluorinated compounds, and relates to a composite catalyst having excellent catalytic activity and durability and capable of substantially rapidly decomposing all perfluorinated compound gases flowing at a high velocity.

[0002] The semiconductor manufacturing process, with its diverse sub-processes, emits a wide variety of hazardous waste gases. Most of these gases are highly volatile, harmful to the human body, and contain highly potent global warming components. Therefore, treatment is essential. Perfluorinated compounds (PFCs), particularly those emitted during the etching and CVD processes of semiconductor manufacturing, are chemically very stable and difficult to break down and dispose of. Their global warming potential is known to be over 7,000 times that of carbon dioxide.

[0003] Typically, perfluorinated compounds can be classified into carbon containing perfluorinated compounds, nitrogen containing perfluorinated compounds, and sulfur-containing perfluorinated compounds containing two or more fluorines (F). Specifically, perfluorinated carbons include CF4, C2F4, C2F6, C3F6, C3F8, C4F8, and C4F. 10 They can be classified into aliphatic compounds, alicyclic compounds, and aromatic perfluorocarbons. NF3 can be an example of perfluoronitrogen, and SF4, SF6 can be an example of perfluorosulfur.

[0004] PFCs are more stable than chlorofluorocarbons (CFCs), which are used as refrigerants, have a higher global warming potential, and take much longer to decompose, resulting in a significantly greater environmental impact. However, as semiconductor microfabrication becomes more precise, demand for PFCs is increasing year by year. Meanwhile, climate change due to global warming is accelerating, leading to progressively stronger environmental regulations on PFCs.

[0005] Catalytic decomposition technology is being utilized in industry as a desirable method for removing PFCs due to its advantages in terms of equipment miniaturization, reduced operating costs, and suppression of NOx production. However, catalytic decomposition technology requires operation at high temperatures of 700°C, and has the disadvantage of poor durability as the catalyst activity decreases over time. Meanwhile, a technology for decomposing PFCs using precious metal catalysts has been reported. However, despite the high cost of the catalyst, the activity of the precious metal catalyst particles decreases as the device is operated at high temperatures, resulting in poor durability. In addition, if the operating temperature is kept low to maintain catalyst activity, a follow-up process of physical adsorption, such as PSA, must be performed.

[0006] Accordingly, there is a need for the development of a catalyst system for PFC decomposition that can catalytically decompose PFCs close to 100% while maintaining constant catalytic activity, has excellent durability, and is economically operable.

[0007] The purpose of the present invention is to provide a composite catalyst for decomposing perfluorinated compounds and a method for removing perfluorinated compounds, which substantially completely decomposes PFCs while maintaining constant catalytic activity and having excellent durability.

[0008] Another object of the present invention is to provide a composite catalyst for decomposing perfluorinated compounds and a method for removing perfluorinated compounds, which can be operated economically by substantially completely decomposing PFCs even at low temperatures.

[0009] Another object of the present invention is to provide a perfluorinated compound removal filter having a very low gas diffusion resistance, which rapidly removes high-velocity perfluorinated compound gases at a high conversion rate, and which has excellent durability by having high coating properties for various types of carriers.

[0010] One aspect of the present invention provides a composite catalyst for decomposing perfluorinated compounds, comprising a carbon body and a porous support coating the surface of the carbon body, wherein the porous support comprises porous alumina.

[0011] According to one embodiment, the carbon body may include a one-dimensional carbon body.

[0012] According to one embodiment, the one-dimensional carbon body may include carbon nanotubes.

[0013] According to one embodiment, the porous alumina may include mesoporous γ-alumina.

[0014] According to one embodiment, in X-ray diffraction analysis (XRD) of the composite catalyst, the ratio of the FWHM1 of the diffraction peak due to the (400) crystal plane of γ-alumina observed in the range of 2θ of 45 to 48° to the FWHM2 of the diffraction peak due to the (440) crystal plane of γ-alumina observed in the range of 65 to 70° (FWHM2 / FWHM1) may be 0.9 to 1.35.

[0015] According to one embodiment, the γ-alumina may be phosphorus-doped.

[0016] According to one embodiment, the γ-alumina may be doped with one or more metals selected from the group consisting of Zn, Zr, Ni, Cr, Sn, Ce, and Co.

[0017] According to one embodiment, the composite catalyst further comprises gold nanoparticles, and the gold nanoparticles may be incorporated within the mesopores.

[0018] According to one embodiment, a plurality of gold nanoparticles may be supported and spaced apart in the longitudinal direction of the one-dimensional carbon body.

[0019] According to one embodiment, the porous support may be positioned conformally in the longitudinal direction of the one-dimensional carbon body and coated with the gold nanoparticles on the surface of the one-dimensional carbon body.

[0020] Another aspect of the present invention provides a perfluorinated compound removal filter comprising a ceramic carrier and a composite catalyst coated on the ceramic carrier, wherein the composite catalyst comprises the composite catalyst as described above.

[0021] Another aspect of the present invention provides a method for removing a hazardous gas, comprising the steps of: S1) heating a reactor including a reaction space filled with a composite catalyst for decomposing a perfluorinated compound; S2) supplying a hazardous gas stream containing a perfluorinated compound into the heated reactor; S3) contacting the hazardous gas stream with the composite catalyst for decomposing a perfluorinated compound to decompose the perfluorinated compound; and S4) discharging a gas stream in which the perfluorinated compound is decomposed; wherein the composite catalyst for decomposing a perfluorinated compound is the composite catalyst for decomposing a perfluorinated compound as described above.

[0022] According to one embodiment, the oxidizing step may be performed at 650°C to 750°C.

[0023] According to one embodiment, the step S2) may further include a step of supplying steam into the heated reactor.

[0024] The composite catalyst for decomposing perfluorinated compounds according to the present invention can substantially decompose PFCs while maintaining constant catalytic activity and thus have excellent durability.

[0025] The composite catalyst for decomposing perfluorinated compounds according to the present invention can substantially completely decompose PFCs even at low temperatures, thereby enabling economic operation of semiconductor manufacturing processes.

[0026] The composite catalyst for decomposing perfluorinated compounds according to the present invention has very low gas diffusion resistance, so it can rapidly remove high-velocity perfluorinated compound gases at a high conversion rate, and it has high coating properties for various types of carriers, so it can provide excellent durability. Specifically, a stable coating layer can be formed simply by immersing a binder-free composite catalyst slurry on a ceramic carrier, making the process very simple and economical, and it can provide a perfluorinated compound removal filter with excellent long-term stability.

[0027] Figure 1 shows a transmission electron microscope photograph of a composite catalyst according to Example 1.

[0028] FIG. 2 shows the FT-IR spectra of the composite catalyst according to Example 1 and γ-alumina according to Comparative Example 1.

[0029] Figure 3 shows the XRD spectra of the composite catalysts according to Examples 1 and 2 and γ-alumina according to Comparative Example 1.

[0030] Figure 4 shows the nitrogen adsorption / desorption isotherm of the composite catalyst according to Example 2.

[0031] Unless otherwise defined, the technical and scientific terms used in this specification have the meaning commonly understood by a person of ordinary skill in the art to which this invention pertains, and descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention are omitted in the following description and accompanying drawings.

[0032] Additionally, the singular forms used herein may be intended to include the plural forms as well, unless the context specifically indicates otherwise.

[0033] In addition, units used in this specification without special mention are based on weight, and for example, units of % or ratio mean weight% or weight ratio, and weight% means the weight% that any one component of the entire composition occupies in the composition unless otherwise defined.

[0034] Additionally, the numerical ranges used herein include lower and upper limits and all values ​​within that range, increments logically derived from the shape and width of the defined range, all doubly defined values, and all possible combinations of upper and lower limits of numerical ranges defined in different shapes. Unless otherwise specifically defined in the specification of the present invention, values ​​outside the numerical range that may arise due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0035] The term "includes" in this specification is an open-ended description equivalent to expressions such as "comprises," "contains," "has," or "characterizes," and does not exclude additional elements, materials, or processes not listed.

[0036] A composite catalyst for decomposing perfluorinated compounds according to the present invention comprises a carbon body and a porous support coating the surface of the carbon body, and the porous support is characterized in that it comprises porous alumina.

[0037] The carbon body may be included in an amount of 0.01 to 5 wt% of the total weight of the composite catalyst, and the porous support may be included in an amount of 95 to 99.99 wt%. Specifically, the carbon body may be included in an amount of 0.02 to 2 wt%, and the porous support may be included in an amount of 98 to 99.98 wt%.

[0038] The carbonaceous body is an inorganic material containing carbon as a main component, and may contain carbon atoms in an amount of 90 atom% or more, 92 atom% or more, 93 atom% or more, or 95 atom% or more, and may contain 100 atom% or less of carbon atoms among the total elements of the carbonaceous body. The carbonaceous body may optionally contain heteroatoms such as nitrogen, boron, phosphorus, or oxygen in an amount of 0 to 10 atom%, 0 to 8 atom%, 0 to 7 atom%, or 0 to 5 atom%. The carbonaceous body may be a one-dimensional carbonaceous body, a two-dimensional carbonaceous body, or a three-dimensional carbonaceous body, and specifically may be any one selected from the group consisting of graphite, graphene, carbon nanotubes, and diamond. Specifically, the carbonaceous body as exemplified may further contain heteroatoms in the amounts as described above.

[0039] According to one embodiment, the carbon body may include a one-dimensional carbon body. The one-dimensional carbon body may refer to a carbon body having an aspect ratio (L / D) of diameter (D) to length (L) of 2 or more, specifically 3 or more, 5 or more, 10,000 or less, 5,000 or less, and for example 2 to 10,000, or 3 to 5,000, but is not limited to a specific numerical range.

[0040] According to one embodiment, the one-dimensional carbon body may include a carbon nanotube. The carbon nanotube may be any one selected from the group consisting of a single-walled carbon nanotube, a double-walled carbon nanotube, and a multi-walled carbon nanotube, but is not limited to a specific material as long as it is a one-dimensional carbon nanotube having an aspect ratio of 2 or more.

[0041] According to one embodiment, the porous alumina may be γ-alumina, θ-alumina, aluminum trihydroxide, boehmite or pseudo-boehmite, and preferably may include γ-alumina.

[0042] According to one embodiment, the composite catalyst may have a structure in which a γ-alumina porous support coats the surface of the carbon nanotube, which is a one-dimensional carbon body, in the longitudinal direction. Accordingly, the specific surface area of ​​the composite catalyst can be significantly increased, and an effective electron transfer path can be provided even when a small amount of one-dimensional carbon body is included.

[0043] According to one embodiment, the γ-alumina may be doped with phosphorus. The phosphorus content may be 0.001 to 1 mol, specifically 0.01 to 0.1 mol, relative to 1 mol of γ-alumina. Alternatively, the phosphorus may be included in an amount of 0.01 to 35 wt%, 0.1 to 20 wt%, 0.2 to 10 wt%, specifically 0.5 to 5 wt%, relative to the total weight of the composite catalyst. When phosphorus is doped in the above amount, the phase change of γ-alumina may be suppressed, thereby improving the stability and durability of the composite catalyst. The phosphorus may be doped with an oxide, and may have, for example, a structure of SO3 or SO4, but is not limited thereto.

[0044] According to one embodiment, the γ-alumina may be further doped with a metal. The metal may be Zn, La, Ga, Zr, Ni, Cr, Sn, Ce, In, B, W, Mg, Ca, Mn, Cu, Ge, Pb, Li, Bi, TI or Co. As the metal is doped, the acid site is improved, so that the operating temperature of the composite catalyst for decomposing perfluorinated compounds is reduced, thereby enabling more economical operation. The metal may be included in an amount of 1 to 40 wt%, 2 to 35 wt%, 5 to 30 wt%, or specifically 10 to 25 wt%, based on the total weight of the composite catalyst.

[0045] According to one embodiment, a composite catalyst comprising a metal and phosphorus in the above content range can have high catalytic activity toward perfluorinated compounds even at relatively low temperatures, and can have excellent durability by maintaining constant catalytic activity even at high temperatures. For example, the composite catalyst can have catalytic activity toward perfluorinated compounds even at temperatures below 550°C, and can maintain constant catalytic activity even at temperatures of 750°C.

[0046] According to one embodiment, the porous support may be a mesoporous support including mesopores, and specifically, may be a mesoporous γ-alumina support.

[0047] The BET specific surface area of ​​the above composite catalyst may be 100 to 500 m2 / g, 150 to 450 m2 / g, 170 to 400 m2 / g, 180 to 350 m2 / g, 180 to 300 m2 / g, 180 to 280 m2 / g or 200 to 250 m2 / g.

[0048] The pore volume of the above composite catalyst is 0.4 to 1.5 cm 3 / g, 0.44 to 1.2 cm 3 / g, 0.5 to 1.2 cm 3 / g, 0.5 to 1.1 cm3 / g, 0.6 to 1 cm 3 / g, 0.65 to 0.95 cm 3 / g, 0.7 to 0.9 cm 3 / g or 0.75 to 0.9 cm 3 / g may be.

[0049] The average pore size of the above composite catalyst may be 7 to 40 nm, 8 to 40 nm, 8 to 30 nm, 8 to 20 nm, 8 to 20 nm, 9 to 20 nm, 10 to 18 nm, or 12 to 18 nm. The BET specific surface area, pore volume, and average pore size may be measured through BET analysis by nitrogen adsorption / desorption. The porous support includes mesopores and has the pore structure described above, thereby providing abundant acid sites for the decomposition of perfluorinated compounds, thereby improving catalytic activity.

[0050] According to one embodiment, the composite catalyst has a BET specific surface area of ​​180 to 280 m2 / g, a BET specific surface area of ​​0.6 to 1 cm 3 / g pore volume, an average pore size of 10 to 18 nm, and more specifically a BET surface area of ​​200 to 250 m2 / g, and 0.7 to 0.9 cm 3 / g pore volume, and an average pore size of 12 to 18 nm.

[0051] The above mesoporous γ-alumina support can form a regular mesoporous structure by being synthesized from a precursor compound of the γ-alumina support in a bottom-up manner, and can provide a significantly higher specific surface area than a conventional porous γ-alumina support. In addition, when doping with phosphorus or a metal, phosphorus or a metal can be uniformly doped throughout the support by being introduced in a bottom-up manner.

[0052] The precursor compound of the above γ-alumina support may be an aluminum compound selected from the group consisting of Al(OR)3 (R is C1-C6 alkyl), AlX3 (X is halogen), and Al(OH)3, and specifically, may be AlX3, and X may be Br, Cl, or I.

[0053] According to one embodiment, the composite catalyst may further comprise gold nanoparticles, iron oxide (Fe3O4) nanoparticles, or zirconia (ZrO2) nanoparticles. Specifically, the composite catalyst may further comprise gold nanoparticles, and the gold nanoparticles may be incorporated within the mesopores. As the gold nanoparticles are supported on the composite catalyst, the acid sites are improved, effectively decomposing perfluorinated compounds at lower temperatures, thereby improving the conversion rate.

[0054] According to one embodiment, the one-dimensional carbon body may have a structure in which a plurality of gold nanoparticles are supported and spaced apart in the longitudinal direction. The gold nanoparticles may be positioned spaced apart from each other without being aggregated individually, and may have a structure in which they are supported on the surface in the longitudinal direction of the one-dimensional carbon body. Accordingly, the one-dimensional carbon body may have a structure in which the surface of the carbon body and the surfaces of the gold nanoparticles are simultaneously exposed.

[0055] According to one embodiment, the porous support may be positioned conformally in the longitudinal direction of the one-dimensional carbon body, and the gold nanoparticles may be coated on the surface of the carbon body. The porous support may function as a coating layer coating the surface of the one-dimensional carbon body. As described above, since the surface of the one-dimensional carbon body and the surface of the gold nanoparticles are simultaneously exposed, the porous support can simultaneously coat the surface of the one-dimensional carbon body and the surface of the gold nanoparticles. By forming such a coating layer, the gold nanoparticles can be stably supported without being separated from the surface of the one-dimensional carbon body.

[0056] According to one embodiment, the porous support may be positioned conformally in the longitudinal direction of the one-dimensional carbon body, and may form a coating layer on the one-dimensional carbon body with the thickness of a thin film. The porous support simultaneously coats the surface of the one-dimensional carbon body and the surface of the gold nanoparticles, and by forming the coating layer with the thickness of a thin film, the diffusion distance for the reactant to diffuse into the gold nanoparticles may be very short and the diffusion resistance may be very low. Accordingly, the composite catalyst according to one embodiment may induce a rapid catalytic reaction of the reactant gas, particularly due to a very low gas diffusion resistance, and the converted product gas may quickly diffuse to the outside, thereby converting the reactant gas with a high flow rate into the product gas at a high conversion rate.

[0057] According to one embodiment, the porous support includes mesopores as described above, and may optionally further include micropores. As used herein, micropores mean that the average diameter of the internal pores is less than 2 nm, and mesopores mean that the average diameter of the internal pores is from 2 nm to 50 nm. The volume of the mesopores of the porous support may be 50% by volume or more, 60% by volume or more, or 70% by volume or more, and the upper limit is not limited, but may be, for example, 100% by volume or less, 95% by volume or less, or 90% by volume or less, or may be 50 to 100% by volume, specifically 60 to 90% by volume, but this is only an example and is not limited thereto.

[0058] In a non-limiting embodiment, the porous support may have a hierarchical porous structure, including a structure in which micropores are regularly present and interconnected between mesopores. However, since the micropores are merely an optional element, the porous support is not limited to a hierarchical porous structure.

[0059] According to a non-limiting embodiment, the porous support may further include macropores, and it may be preferable to include macropores in a certain volume fraction or more, thereby significantly reducing the diffusion resistance of the gas.

[0060] According to one embodiment, the nitrogen adsorption / desorption isotherm of the composite catalyst may have hysteresis. In addition, the closing point of the relative pressure (P / P0) where the adsorption curve and the desorption curve meet may be located between 0.45 and 0.65, specifically between 0.48 and 0.6 or between 0.5 and 0.55.

[0061] According to one embodiment, in X-ray diffraction analysis (XRD) of the composite catalyst, the ratio (FWHM2 / FWHM1) of the diffraction peak due to the (400) crystal plane of γ-alumina observed in the range of 2θ of 45 to 48°, specifically around 46°, to the FWHM2 of the diffraction peak due to the (440) crystal plane of γ-alumina observed in the range of 65 to 70°, specifically around 67°, may be 0.9 to 1.35. More specifically, the ratio (FWHM2 / FWHM1) may be 0.95 to 1.3, 0.95 to 1.25, 0.95 to 1.2, 0.95 to 1.15, 0.95 to 1.1, or 0.98 to 1.1. As the above (400) and (440) crystal planes satisfy the above ratio, the composite catalyst can maintain constant catalytic activity at higher temperatures and have excellent durability.

[0062] According to one embodiment, in the infrared spectroscopy analysis of the composite catalyst, 400 to 1250 cm -1 It may have an absorption halo peak that is not observed as multiple peaks in the range of 400 to 1250 cm -1In the range of Al-O, the absorption due to stretching can be significantly reduced, and in contrast, γ-alumina without carbon can have a very strong and broad halo peak in the same wavenumber range. Meanwhile, in the infrared spectroscopy (FT-IR) analysis of the γ-alumina particles, the halo peak at 1630 cm -1 It can have an absorption peak due to Al-O symmetrical bending.

[0063] The above gold nanoparticles can be manufactured by a method known in the art or can use commercially available materials. Specifically, the gold nanoparticles can be manufactured by reducing a gold precursor present in a solution to gold according to a known method (Natan et al., Anal. Chem. 67, 735 (1995)). Examples of the gold precursor include, but are not limited to, gold-containing halides, nitrates, acetates, acetylacetonates, or ammonium salts. Specifically, the gold precursor can be, but is not limited to, HAuCl4 or HAuBr4.

[0064] The diameter of the above gold nanoparticles may be 1 to 20 nm, specifically 1 to 15 nm, and more specifically 1 to 12 nm. A preferred diameter of the gold nanoparticles may be 1 to 10 nm, and more preferably 1 to 8 nm.

[0065] According to one embodiment, the gold nanoparticles may be incorporated into all or part of the mesopores of the porous support, and according to a preferred embodiment, the gold nanoparticles may be incorporated into part of the mesopores of the porous support. More specifically, the nanoparticles may be irregularly incorporated into part of the mesopores of the porous support.

[0066] At this time, the structure embedded in all of the mesopores of the porous support means a superlattice structure, and specifically, means a highly ordered superlattice structure having face-centered cubic (FCC) symmetry. The form in which gold nanoparticles are irregularly embedded in some of the mesopores means that the gold nanoparticles are embedded in some of the mesopores of the porous support in a random form, and has the advantage of allowing gas diffusion to occur more effectively compared to the superlattice structure.

[0067] According to one embodiment, the gold nanoparticles are incorporated into a portion of the mesopores of the porous support, and the mesopores in which the gold nanoparticles are not incorporated may be interconnected by open pores. Since the composite catalyst has the gold nanoparticles incorporated only into a portion of the pores of the porous support, the diffusion of harmful gases may be more effectively achieved through the pores in which the nanoparticles are not incorporated and are interconnected by open pores. For example, the gold nanoparticles may be incorporated in an amount of 50% by volume or less, 50% by volume or less, 40% by volume or less, 30% by volume or less, 20% by volume or less, or 10% by volume or less, based on the total volume of the mesopores of the porous support, and may also be incorporated in an amount of 0.01% by volume or more, 0.05% by volume or more, 0.1% by volume or more, 0.5% by volume or more, or 1% by volume or more, but is not limited thereto. Alternatively, the gold nanoparticles may be included in an amount of 0.01 to 50% by volume, 0.05 to 40% by volume, 0.1 to 30% by volume, 0.5 to 20% by volume, or 1 to 10% by volume relative to the total volume of the mesopores of the porous support, but is not limited thereto.

[0068] According to one embodiment, the composite catalyst may have an average particle diameter of, but is not limited to, 0.01 ㎛ to 20 mm, specifically, 0.05 ㎛ to 10 mm, and more specifically, 0.1 ㎛ to 5 mm. The average diameter refers to an average value calculated by measuring the major axis length of individual particles in a microscope photograph, adding up the major axis diameters, and dividing by the number of particles. The number of particles for calculating the average value may be 50 to 200, and for example, the average diameter may be an average value measured after randomly selecting 100 particles. The shape of the composite catalyst is not limited to a specific shape, and examples thereof include, but are not limited to, powder formation, bead shape, cylinder shape, ring shape, plate shape, or fiber shape.

[0069] In one embodiment, the composite catalyst can decompose perfluorinated compounds, but can also decompose substantially all of perfluorocarbon, perfluoronitrogen and perfluorosulfur to convert them into products such as carbon dioxide and HF or fluorine gas.

[0070] In addition, the present invention provides a perfluorinated compound removal filter, wherein the perfluorinated compound removal filter comprises a ceramic carrier and a composite catalyst coated on the ceramic carrier, wherein the composite catalyst comprises the composite catalyst as described above.

[0071] According to one embodiment, the ceramic carrier may have various shapes such as spherical, cylindrical or polygonal, but may be selected without being limited to a specific shape.

[0072] According to one embodiment, the ceramic carrier may be a porous ceramic carrier, and the porous carrier may have channels through which gas may pass therethrough. The ceramic carrier may be a monolithic honeycomb ceramic carrier. The honeycomb ceramic structure may be a structure having a plurality of gas flow channels, and the cross-section of the flow channels may have various shapes such as a polygon such as a square or a hexagon, a circle, etc., but is not limited to a specific shape and may be selected. The honeycomb ceramic structure may be one or two or more selected from the group consisting of a metal oxide, a metalloid oxide, a metal carbide, and a metalloid carbide. Specific examples include, but are not limited to, alumina, silica, silicon carbide, etc.

[0073] According to one embodiment, the composite catalyst coated on the ceramic carrier may be manufactured from a step of forming a coating layer by coating an aqueous slurry containing a composite catalyst powder on a porous substrate and a step of sintering the porous substrate on which the coating layer is formed.

[0074] The above aqueous slurry may have a weak acidity of pH 2 to 6, but is not limited thereto.

[0075] According to a non-limiting embodiment, the aqueous slurry may further comprise one or more binders selected from the group consisting of an inorganic sol binder and a water-soluble polymer binder. The inorganic sol binder may have an average particle diameter of 1 to 50 nm, and may be included in an amount of 1 to 20 parts by weight based on dry weight relative to 100 parts by weight of the composite catalyst powder, but is not limited thereto. The inorganic sol binder may be, but is not limited to, silica sol, titania sol, or alumina sol.

[0076] The water-soluble polymer binder may be one or more selected from the group consisting of polyethylene glycol, polyvinyl alcohol, and poly(N-vinyl pyrrolidone). The water-soluble polymer binder may be included in the aqueous slurry in an amount of 1 to 5 wt%, but is not limited thereto. The weight average molecular weight of the water-soluble polymer binder may be 10,000 to 1,000,000 g / mol, but is not limited thereto.

[0077] The composite catalyst as described above has high coating properties for various types of ceramic carriers and can have excellent durability that does not easily peel off from the ceramic carrier.

[0078] According to one embodiment, the composite catalyst may be mixed with a solvent and provided as a slurry composition for coating. A coating layer of the composite catalyst can be formed on the surface of the ceramic carrier simply by immersing the ceramic carrier in the coating slurry composition and drying it. As an advantageous effect, the coating slurry composition can form a stable coating layer on the ceramic carrier even without containing the binder described above, so that it has excellent long-term stability and can provide an advantage in the process in that it does not require an additional calcination or heat treatment step. That is, it can have the advantage that a stable coating layer can be formed only by the step of coating an aqueous slurry composed of a composite catalyst powder on a ceramic carrier to form a coating layer and the step of drying the ceramic carrier on which the coating layer has been formed.

[0079] The present invention provides a system for removing a hazardous gas, comprising: a gas inlet through which a hazardous gas stream containing a perfluorinated compound is introduced; a gas outlet through which a gas stream from which a perfluorinated compound has been removed is discharged; and a catalytic reaction unit having the gas inlet and the gas outlet connected to their respective ends and including a reaction space in which a composite catalyst for decomposing a perfluorinated compound is accommodated, wherein the composite catalyst for decomposing a perfluorinated compound is characterized in that it is a composite catalyst for decomposing a perfluorinated compound according to one embodiment described above.

[0080] The shape of the above catalytic reaction unit is not limited to a specific shape, and may have a tubular shape, for example. The catalytic reaction unit is provided with a duct through which a gas stream flowing from a sealed space can pass, and the duct is provided with a reaction space, and a complex catalyst for decomposing perfluorinated compounds is filled in the reaction space. Since the complex catalyst for decomposing perfluorinated compounds is hermetically filled in the reaction space, the gas stream flowing into the duct comes into contact with the complex catalyst particles and passes through the reaction space. Accordingly, the perfluorinated compound contained in the gas stream comes into contact with the complex catalyst for decomposing perfluorinated compounds, and is converted into gases such as carbon dioxide and HF, and can be removed from the gas stream.

[0081] According to one embodiment, the toxic gas removal system may further include a heat source that supplies thermal energy. The thermal energy may be supplied to the catalytic reaction unit to heat and maintain the temperature of the reaction space at a constant temperature. In addition, the toxic gas stream containing the perfluorinated compound may also be heated by the heat source before flowing into the catalytic reaction unit, and brought into contact with the composite catalyst for decomposing the perfluorinated compound in the catalytic reaction unit at a set temperature.

[0082] According to one embodiment, the gas inlet may further include water vapor in the hazardous gas stream containing the perfluorinated compound. Through one gas inlet, the perfluorinated compound and water vapor are mixed and introduced into the catalytic reaction unit, where the perfluorinated compound can be removed by hydrolysis within the catalytic reaction unit.

[0083] According to another embodiment, the toxic gas removal system may further include a gas inlet through which water vapor may be introduced at one end of the catalytic reaction section. The gas inlet through which the water vapor is introduced may be introduced into the catalytic reaction section in the same direction as the gas inlet through which the toxic gas stream containing the perfluorinated compound is introduced, and the two gas inlets may be positioned in a direction opposite to the gas outlet with respect to the catalytic reaction section.

[0084] According to one embodiment, a post-treatment unit may be further included at one end of the gas outlet. The post-treatment unit can trap HF gas removed by decomposition of the perfluorinated compound to prevent it from being discharged to the outside. The post-treatment unit may be selected without limitation as long as it is a means capable of removing HF gas by physically or chemically adsorbing, absorbing, or chemically converting it. For example, the post-treatment unit may be an adsorbent including a solid adsorbent capable of physically or chemically adsorbing HF gas in a gas stream from which the perfluorinated compound has been removed; an absorbent including a neutral or basic aqueous solution capable of dissolving HF gas; or a reactant including a solid reactant capable of chemically reacting with HF gas. For a more specific example, the post-treatment unit may be a column filled with calcium oxide (CaO) as a solid reactant, and the calcium oxide may chemically react with the HF gas included in the exhaust gas stream to remove it. Alternatively, the post-treatment unit may be an aqueous solution containing an alkali metal hydroxide as a liquid absorbent. Examples of the alkali metal hydroxide include, but are not limited to, LiOH, KOH, or NaOH. The aqueous solution containing the alkali metal hydroxide chemically reacts with the HF gas contained in the exhaust gas stream to produce an alkali metal fluoride salt, thereby removing the HF gas.

[0085] According to one embodiment, the gas inlet may further include a pretreatment unit for pretreating a gas stream containing a perfluorinated compound, located upstream or downstream of the gas inlet. The pretreatment unit can remove various impurities contained in the gas stream containing the perfluorinated compound, particularly substances that can reduce the activity of the composite catalyst or poison the catalyst. Specific examples of the pretreatment unit include a filter capable of physically removing the impurities; or an absorbent containing a neutral or basic aqueous solution capable of dissolving the impurities.

[0086] In addition, the present invention provides a method for removing a toxic gas, comprising the steps of: S1) heating a reactor including a reaction space filled with a composite catalyst for decomposing a perfluorinated compound; S2) supplying a toxic gas stream containing a perfluorinated compound into the heated reactor; S3) contacting the toxic gas stream with the composite catalyst for decomposing a perfluorinated compound to decompose the perfluorinated compound; and S4) discharging a gas stream in which the perfluorinated compound is decomposed; wherein the composite catalyst for decomposing a perfluorinated compound is the same composite catalyst for decomposing a perfluorinated compound as described above.

[0087] The method for removing the above perfluorinated compound can more effectively cause the oxidation reaction of the perfluorinated compound in a high-velocity gas stream by using a composite catalyst exhibiting remarkably excellent catalytic activity as described above.

[0088] The above-mentioned hazardous gases may be generated during semiconductor or LCD manufacturing processes. The removal method according to the present invention is advantageous in that it substantially decomposes perfluorinated compound gases generated during semiconductor or LCD manufacturing processes, thereby suppressing the acceleration of global warming.

[0089] According to one embodiment, the temperature of the step S3) may be performed at 500°C to 900°C, specifically 600°C to 800°C, and more specifically 650°C to 750°C, but is not necessarily limited thereto.

[0090] According to one embodiment, in the step S4), a post-treatment step may be further included at one end of the gas outlet. In the post-treatment step, HF gas removed by the decomposition of the perfluorinated compound may be trapped to prevent its discharge to the outside. Since the post-treatment step is identical to the technical characteristics of the post-treatment unit described above, a detailed description thereof will be omitted.

[0091] According to one embodiment, the step S2) may further include a pretreatment step for pretreating a gas stream from which perfluorinated compounds have been removed, at a front or rear end of the gas inlet. In the pretreatment step, various impurities contained in the gas stream from which perfluorinated compounds have been removed, particularly substances that may lower the activity of the catalyst or poison the catalyst, can be removed. Since the pretreatment step is identical to the technical features of the pretreatment unit described above, a detailed description thereof will be omitted.

[0092] According to one embodiment, the perfluorinated compound can be removed with a removal rate of 90% or more, specifically 95% or more, and more specifically 99% or more, under a flow rate condition of 1,000 ml / min by the method for removing a hazardous gas as described above. Specifically, the perfluorinated compound can be removed with a removal rate in the above-described range at the above-described temperature range.

[0093] Hereinafter, the present invention will be described in more detail using examples. However, the following examples are provided only to help understand the present invention, and the technical idea of ​​the present invention is not limited to the following examples.

[0094]

[0095] (Example 1) Preparation of composite catalyst 1

[0096] [Step 1]: Preparation of carbon nanotube (CNT) dispersion

[0097] A CNT dispersion was prepared by adding 0.3 g of CNT and 10.9 g of Pluronic F127 to 100 ml of distilled water, mixing, and irradiating with ultrasound for 1 hour.

[0098] [Step 2]: Preparation of porous boehmite-CNT composite

[0099] A mixed dispersion was prepared by adding 0.13 g of phosphoric acid, 0.08 g of disodium phosphate, and 5.5 g of aluminum sec-butoxide to 60 ml of the CNT dispersion prepared in the above [Step 2]. The mixed dispersion was stirred at room temperature for 2 hours to prepare a precipitate. The precipitate corresponds to a porous boehmite-CNT composite.

[0100] [Step 3]: Preparation of composite catalyst

[0101] The precipitate prepared in the above [Step 3] was washed with water, dried, and calcined at 500°C for 4 hours to remove the Pluronic F127 polymer, thereby preparing composite catalyst 1, which is a porous γ-alumina-CNT composite.

[0102] (Example 2) Preparation of composite catalyst 2

[0103] The same procedure as in Example 1 was followed, except that 3 g of AlCl3 was used instead of aluminum sec-butoxide in step 2 of Example 1, and a porous γ-alumina-CNT composite was prepared by calcining at 500°C for 4 hours in step 3.

[0104] (Example 3) Preparation of composite catalyst 3

[0105] P was doped into the composite catalyst 2 manufactured in Example 2 above. The specific manufacturing method is as follows.

[0106] A mixture was prepared by adding 20 ml of an aqueous solution containing 0.1 g of phosphoric acid to 4 g of the complex catalyst 2 and mixing uniformly for 1 hour. Thereafter, the mixture was dried in an oven at 120°C for 2 hours and calcined at 500°C for 4 hours to prepare a zinc- and phosphorus-doped complex catalyst.

[0107] (Example 4) Preparation of composite catalyst 4

[0108] [Step 1]: Preparation of polymer-functionalized gold nanoparticles

[0109] [Step 1-1]: Gold nanoparticles stabilized with oleylamine are synthesized according to the following procedure.

[0110] First, olein amine was selected as a stabilizer, and a solution composed of 60 ml of toluene, 60 ml of oleylamine, and 0.6 g of HAuCl·3H2O was prepared by stirring at room temperature for 10 minutes. 6 mmol of tetrabutylamine borane complex, 6 ml of toluene, and 6 ml of oleylamine were mixed by ultrasonication and quickly added to the solution. The solution was stirred at room temperature for another hour, ethanol was added, and centrifuged to precipitate gold nanoparticles. The gold nanoparticle precipitate was redispersed in toluene, ethanol was added, and centrifuged. The prepared gold nanoparticles exhibited an average particle diameter of 4 nm, and the prepared gold nanoparticles were dispersed in 100 ml of toluene as formed.

[0111] [Step 1-2]: The surface of gold nanoparticles is functionalized with thiolated PEG using the following method.

[0112] In the above step 1-1, the gold nanoparticles dispersed in toluene were diluted by adding an additional 100 ml of tetrahydrofuran, and a thiolated polymer was selected to functionalize the surface of the gold nanoparticles by binding the polymer to the surface, and 1 g of monofunctional polyethylene glycol (aSH-PEG, weight average molecular weight: 1 kDa) with a thiol group substituted at the terminal was added. After stirring, hexane was added, and centrifugation was performed to precipitate gold nanoparticles (Au-PEG) functionalized with PEG. The Au-PEG obtained by precipitation was dried and dispersed in water.

[0113] [Step 2]: Preparation of carbon nanotube (CNT) dispersion

[0114] A CNT dispersion was prepared by adding 0.3 g of CNT and 10.9 g of Pluronic F127 to 100 ml of distilled water, mixing, and irradiating with ultrasound for 1 hour.

[0115] [Step 3]: Preparation of porous boehmite-CNT composites encapsulating gold nanoparticles.

[0116] A uniform dispersion was prepared by mixing 1 g of the Au-PEG prepared in [Step 1-2] and 3.7 g of the activator Pluronic F127 in 100 ml of distilled water. To the dispersion, 60 ml of the CNT dispersion prepared in [Step 2], 0.13 g of phosphoric acid, 0.08 g of disodium phosphate, and 5.5 g of aluminum sec-butoxide were added to prepare a mixed dispersion. The mixed dispersion was stirred at room temperature for 2 hours to prepare a precipitate. The precipitate corresponds to a porous boehmite-CNT composite in which gold nanoparticles are captured.

[0117] [Step 4]: Preparation of composite catalyst

[0118] The precipitate prepared in the above [Step 3] was washed with water, dried, and calcined at 500°C for 4 hours to remove PEG and Pluronic F127 polymers, thereby preparing composite catalyst 4.

[0119] (Example 5) Preparation of composite catalyst 5

[0120] Composite catalyst 5 was manufactured by performing the same steps as in [Step 1-1] of the above Example 2, except that gold nanoparticles having an average particle size of 10 nm were manufactured by adjusting the molar ratio of oleylamine and HAuCl·3H2O.

[0121] (Example 6) Manufacturing of a harmful gas removal filter

[0122] The composite catalyst 1 prepared in Example 1 was mixed in an aqueous solution to make 10 wt% and milled to prepare a coating slurry. The average particle diameter of the milled composite catalyst powder was 1.13 μm. The inorganic binder silica sol was mixed into the slurry to make 1 wt% of the dispersion.

[0123] The surface of gamma alumina balls with an average diameter of 4 mm was dip-coated with the above coating slurry for 5 minutes, and then the excess slurry was removed by blowing air and then thoroughly dried. The dipping and drying process was repeated 10 times. The coated gamma alumina balls were placed in a vacuum oven and dried at 150°C for 1 hour to finally manufacture a harmful gas removal filter.

[0124] (Comparative Example 1)

[0125] The same procedure as Example 1 was followed, except that porous γ-alumina was prepared without including a CNT dispersion.

[0126] (Comparative Example 2)

[0127] The same procedure as Example 6 was followed, except that the composite catalyst 1 prepared in Example 1 was not used in Example 6, but the composite catalyst of Comparative Example 1 was used.

[0128] (Experimental Example 1) Fourier transform infrared spectroscopy (FT-IR) analysis

[0129] To obtain FT-IR spectra, the composite catalysts according to the examples and comparative examples were pulverized and then measured using an FT-IR spectrometer (Nicolet iS50, Thermo Fisher Scientific Instrument).

[0130] Referring to Figure 2, in infrared spectroscopy analysis, 400 to 1250 cm -1 In the wavelength range of , the composite catalyst according to Example 1 can be observed to have a broad and weak absorption halo peak that is not observed as multiple peaks. Conventional γ-alumina has a broad absorption halo peak in the range of 400 to 1250 cm -1 It is known that the absorption due to stretching of Al-O in the wavenumber range is very strong and has a broad absorption halo peak. However, the composite catalyst according to Example 1 has a peak at 1630 cm -1It was found that the absorption intensity was similar to the absorption peak due to the symmetrical bending of γ-alumina observed in . Meanwhile, the γ-alumina according to Comparative Example 1 had an absorption intensity of 400 to 1250 cm -1 It was found that the composite catalyst according to the example has very strong and broad halo peaks in the range of . From the above results, it is understood that the composite catalyst according to the example has different chemical properties compared to the γ-alumina of comparative example 1.

[0131] (Experimental Example 2) X-ray diffraction (XRD) analysis

[0132] After crushing the composite catalyst according to the examples and comparative examples, X-ray diffraction (XRD, Rigaku D / MAX-2500 / PC, 40 kV, 15 mA, 4° min -1 , Cu-Kα radiation, λ = 0.15406 nm) to confirm the structure. The composite catalysts according to each example and comparative example were heat-treated in air at 700°C for 4 hours to remove CNTs and measured to accurately confirm the phase of γ-alumina. The Full Width at Half-Maximum (FWHM) of the Bragg peaks of the (400) and (440) crystal planes, where 2q appears at approximately 46° and 67°, were calculated and designated as FWHM1 and FWHM2, respectively. The calculation results are shown in Table 1.

[0133] (400) FWHM1 (440) FWHM2 FWHM2 / FWHM1 Example 12.02 92.15 61.062 Example 23.08 23.13 31.016 Comparative Example 11.70 62.53 21.442

[0134] Referring to Table 1 and FIG. 3, both Examples 1 and 2 have a ratio of the full width at half maximum (FWHM2 / FWHM1) of around 1, indicating that the grain sizes along the (400) and (440) crystal planes of γ-alumina are substantially the same. In contrast, the γ-alumina according to Comparative Example 1 has a ratio of the full width at half maximum that greatly exceeds 1. This means that the grain size along the (440) crystal plane is larger than the grain size along the (400) crystal plane. Although the exact mechanism is not known, it appears that maintaining the grain sizes along the (400) and (440) crystal planes to be substantially the same has a significant effect on the catalytic activity and durability of the composite catalyst.

[0135] (Experimental Example 3) Pore Characteristics Analysis

[0136] To determine the specific surface area and pore structure of the composite catalysts according to the examples and comparative examples, nitrogen adsorption experiments were performed using a TriStar II 3020 (Micromeritics). Prior to nitrogen adsorption analysis, the samples were pretreated for 8 hours in a vacuum at 150°C, and then nitrogen adsorption and desorption were performed to calculate the BET (Brunauer-Emmett-Teller) specific surface area, pore volume, average pore size, and BJH specific surface area. The calculation results are shown in Table 2.

[0137] BET surface area (m 2 / g)BJH specific surface area (m 2 / g) pore volume (cm) 3 / g)Average pore size (nm)Closed pointExample 1245.12302.110.8914.550.53Example 2230.92281.320.8715.090.52Example 3172.52218.740.6916.280.51Comparative example 1191.49258.610.428.820.45

[0138] Referring to Table 2 and Figure 4, both Examples 1 and 2 are 200 m 2BET surface area of ​​more than / g, 270 m 2 BJH surface area of ​​more than / g, 0.5 cm 3 / g or more of pore volume. In particular, the significant increase in pore volume due to the inclusion of CNTs was an unexpected result, suggesting that the reactants can easily diffuse into the composite catalyst due to the very high pore volume. Although mesoporosity is common to both the examples and comparative examples, the significant increase in the average pore size to more than 14 nm in the examples appears to be a very advantageous factor for increasing catalytic activity in the same sense as the pore volume.

[0139] (Experimental Example 4) Durability test of a harmful gas removal filter

[0140] An accelerated durability test was performed to compare the catalyst residue rate before and after ultrasonic cleaning by sufficiently submerging the harmful gas removal filter of Example 6 in water and applying 400 W of ultrasonic waves for 60 minutes. The accelerated durability test results showed that the catalyst residue rate was 96%, but in the case of Comparative Example 2, the catalyst residue rate was 68%. From this, it was shown that the harmful gas removal filter of Example 6 had excellent durability.

[0141] (Experimental Example 5) Evaluation of removal of perfluorinated compounds

[0142] 10g of the composite catalyst according to the examples and comparative examples was filled into an Inconel reaction tube with an outer diameter of 1", and CF was placed on one side of the reaction tube. 4　 The gas was supplied as 3,000 ppm, water vapor (H2O) 20 vol%, and air balance, and the other side of the reaction tube was connected to an IR analyzer to measure the concentration of CF4 discharged from the other side of the reaction tube. Specifically, water vapor was 100 ㎖ / min, air 400 ㎖ / min, CF 4　 It is supplied to the reaction tube at a flow rate of 1.5 ml / min, and the space velocity is 2,100 h -1The reaction tube was heated to 700 ℃, and the discharged CF 4　 The concentration of CF was measured. 4　 The conversion rate was calculated as follows.

[0143] CF 4　 Conversion (%) = (1-C out / C in ) x 100

[0144] C in is the incoming CF4 concentration, C out is the CF4 concentration after passing through the reaction tube. The concentration of CH2F2 discharged every hour for 10 hours was measured while maintaining the reaction tube at 700℃. The conversion rate is shown in Table 3.

[0145] Conversion rate (%) 1h2h4h6h8h10hExample 198%97%95%92%89%83%Example 299%99%97%94%91%88%Example 391%92%91%91%90%91%Example 499%98%96%94%91%86%Comparative example 195%94%91%86%79%70%

[0146] Referring to Table 3, it was confirmed that the composite catalyst according to the example maintained excellent catalytic activity. On the other hand, it was confirmed that the catalytic activity of Comparative Example 1 rapidly decreased. As described above, the present invention has been described by specific matters and limited examples and drawings, but these are provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations from these descriptions.

[0147] Therefore, the idea of ​​the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the following claims as well as the claims are considered to fall within the scope of the idea of ​​the present invention.

Claims

1. Contains a carbon body and a porous support coating the surface of the carbon body, A composite catalyst for decomposing perfluorinated compounds, characterized in that the porous support comprises porous alumina.

2. In paragraph 1, The above carbon body is a composite catalyst for decomposing perfluorinated compounds, comprising a one-dimensional carbon body.

3. In paragraph 2, The above one-dimensional carbon body is a composite catalyst for decomposing perfluorinated compounds, comprising carbon nanotubes.

4. In paragraph 1, The above porous alumina is a composite catalyst for decomposing perfluorinated compounds, comprising mesoporous γ-alumina.

5. In paragraph 4, A composite catalyst for decomposing perfluorinated compounds, wherein the ratio (FWHM2 / FWHM1) of the diffraction peak due to the (400) crystal plane of γ-alumina observed in the range of 2θ of 45 to 48° and the FWHM2 of the diffraction peak due to the (440) crystal plane of γ-alumina observed in the range of 65 to 70° in X-ray diffraction analysis (XRD) of the above composite catalyst is 0.9 to 1.

35.

6. In paragraph 1, The above γ-alumina is a composite catalyst for decomposing perfluorinated compounds, wherein the composite catalyst is phosphorus-doped.

7. In paragraph 1, A composite catalyst for decomposing perfluorinated compounds, wherein the above γ-alumina is doped with one or more metals selected from the group consisting of Zn, Zr, Ni, Cr, Sn, Ce, and Co.

8. In paragraph 1, A composite catalyst for decomposing perfluorinated compounds, wherein the composite catalyst further comprises gold nanoparticles, and the gold nanoparticles are incorporated within the mesopores.

9. In paragraph 8, A composite catalyst for decomposing perfluorinated compounds, wherein a plurality of gold nanoparticles are supported and spaced apart in the longitudinal direction of the one-dimensional carbon body.

10. In paragraph 8, A composite catalyst for decomposing perfluorinated compounds, wherein the porous support is positioned conformally in the longitudinal direction of the one-dimensional carbon body and the gold nanoparticles are coated on the surface of the one-dimensional carbon body.

11. Comprising a ceramic carrier and a composite catalyst coated on the ceramic carrier, A filter for removing perfluorinated compounds, characterized in that the complex catalyst comprises a complex catalyst according to any one of claims 1 to 10. 12.S1) A step of heating a reactor including a reaction space filled with a complex catalyst for decomposing a perfluorinated compound; S2) A step of supplying a hazardous gas stream containing a perfluorinated compound into the heated reactor; S3) a step of contacting the hazardous gas stream with the complex catalyst for decomposing the perfluorinated compound to decompose the perfluorinated compound; and S4) A step of discharging a gas stream in which the above perfluorinated compound is decomposed; including; A method for removing a hazardous gas, wherein the complex catalyst for decomposing a perfluorinated compound is a complex catalyst for decomposing a perfluorinated compound according to any one of claims 1 to 10.

13. In paragraph 12, A method for removing a harmful gas, wherein the above oxidation step is performed at 650°C to 750°C.

14. In paragraph 12, A method for removing a harmful gas, further comprising, in the step S2), a step of supplying steam into the heated reactor.

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