KR100402430B1 - Catalyst for decomposition of toxic pollutants and producing process thereof - Google Patents

Abstract

The present invention relates to a catalyst for simultaneously decomposing toxic contaminants including chlorine-based compounds and nitrogen oxides emitted from a combustion process, wherein titanium dioxide (TiO ₂ ) and alumina (Al ₂ O ₃ ) are coated on the cordialite surface. The vanadium (V) is supported as a catalytically active component on the cordialite-titanium dioxide-alumina support, and the crystallinity of the titanium dioxide measured by the X-ray diffraction method is 10 to 20%.

Description

Catalyst for decomposition of toxic pollutants and its preparation method {Catalyst for decomposition of toxic pollutants and producing process}

The present invention relates to a catalyst for decomposing toxic pollutants and a method for manufacturing the same, and more particularly, a catalyst capable of decomposing chlorine-based compounds and nitrogen oxides such as dioxins discharged from incineration or combustion processes into less toxic or harmless substances, and It relates to a manufacturing method.

The gas emitted from incineration or combustion processes such as thermal power plants, industrial incinerators, municipal waste incinerators, hospital waste incinerators, furnaces, boilers, etc. Dibenzo-p-dioxin / polychlorinated dibenzofuran, polychlorinated biphenyl (PCB), benzene chloride, phenol chloride, volatile organic compound (VOC), etc. In recent years, as the operation of combustion and incineration processes that produce a large amount of such toxic compounds increases, serious environmental pollution problems are raised.

In addition, a large amount of nitrogen oxides are generated in the combustion and incineration processes due to fuel components and high flame temperatures. These nitrogen oxides are known to cause acid rain to destroy environmental ecosystems.

Adsorption, thermal incineration, and scrubbing have been used to treat existing chlorine compounds, and selective catalytic reduction (SCR) is most commonly used to decompose nitrogen oxides.

Adsorption is a method of adsorbing and removing combustion exhaust gas through an adsorbent layer such as activated carbon or coke, zeolite, etc., but it is not applicable to the treatment of toxic compounds contained at low concentrations with low removal efficiency. In addition, the continuous use of the adsorbent is not only possible, but incineration of the discarded adsorbent has a problem that the toxic compounds are regenerated, and when the landfill is buried has a big problem of contaminating groundwater.

The cleaning method is a method of contacting the exhaust gas with a chemical solution, which is effective for removing acidic gas and particulate matter contained in the exhaust gas, but a large amount of chemical wastewater is generated, which causes pollution and does not remove toxic compounds having low solubility.

On the other hand, decomposition of nitrogen oxides can be removed with high efficiency by selective catalytic reduction. Catalytic reduction is a method of injecting ammonia and decomposing it into nitrogen by reduction of nitrogen oxides in the catalyst. Specific examples include TiO ₂ and Al ₂ O ₃ , SiO ₂ , V ₂ O ₅ , WO ₃ , Pt, Pd, etc. in US Pat. Nos. 4,085,193, Formulations 4,018,706, 4,059,675, 4,059,676 and 4,059,683. A method of treating nitrogen oxides at high efficiency using a constructed catalyst is disclosed.

US Pat. No. 5,512,259 relates to a process using a catalyst capable of simultaneously removing dioxins and nitrogen oxides, which have 70 to 80 weight percent TiO ₂ , 0 to 10 weight percent WO ₃ , 0.5 to 3 A process for decomposing halogen compounds under oxidation reaction conditions and reducing nitrogen oxides under reduction reaction conditions in which ammonia is injected is carried out using a honeycomb catalyst comprising a wt% of V ₂ O ₅ and 0 to 5 wt% of MoO ₃ . Doing. However, the patent is similar to the catalyst used in the selective catalytic reduction process (SCR), which is a modification of the catalyst used for removing nitrogen oxide as it is or by adding a donor metal. Therefore, the catalyst has a disadvantage in that chlorine-based aromatic compounds such as dioxin are converted into organic compounds having low efficiency and low efficiency from being decomposed into carbon monoxide, carbon dioxide, water, hydrochloric acid, and chlorine gas. In addition, since the BET surface area is small to 20 to 100 m ² / g, sintering of the metal particles easily occurs, so that there is a disadvantage in that the decomposition activity greatly decreases when used for a long time.

US Pat. Nos. 5,387,734 and 5,276,250 also disclose processes for removing dioxins with high efficiency using catalysts in which Zn, Ni, Cr, Cu, Fe, Pt, Rh or their oxides are supported on silica-alumina carriers. U.S. Patent No. 5,260,044 describes a process for decomposing dioxins (PCDDs / PCDFs) using a honeycomb shaped catalyst in which platinum is supported on a 60% by weight TiO ₂ -Mulite (3Al ₂ O _{3 ·} 2SiO ₂ ) support. It is starting. However, the catalyst has a disadvantage in that a large space velocity (SV) is required because the decomposition activity is low due to poor dispersibility of the metal supported on the carrier and sintering of the metal component during the thermal firing of the catalyst. have.

Accordingly, the technical problem to be achieved by the present invention is to provide a catalyst capable of maintaining a high efficiency for a long time without providing a suitable surface area for decomposition of toxic compounds and at the same time does not decrease the decomposition efficiency due to the sintering of metal components.

In addition, another technical problem to be achieved by the present invention is to provide a method for producing the catalyst.

In order to achieve the above technical problem of the present invention

A vanadium (V) is supported as a catalytically active component on a cordialite-titanium dioxide-alumina carrier formed by coating titanium dioxide (TiO ₂ ) and alumina (Al ₂ O ₃ ) on the cordialite surface. It provides a catalyst for the decomposition of toxic pollutants, characterized in that the crystallinity of the titanium dioxide measured by 10 to 20%.

According to an embodiment of the present invention, the content of the titanium dioxide is preferably 6 to 12% by weight based on the total weight of the catalyst.

According to an embodiment of the present invention, the content of the alumina is preferably 10 to 30% by weight based on the total weight of the catalyst.

According to an embodiment of the present invention, it is preferable that the content of vanadium is 1 to 6% by weight based on the weight of titanium dioxide.

According to another embodiment of the present invention, the catalytically active ingredient further comprises at least one metal or metal oxide selected from the group consisting of molybdenum (Mo), tungsten (W), palladium (Pd) and oxides thereof. It is preferable.

According to another embodiment of the present invention, the content of the metal or metal oxide is preferably 9% by weight or less based on the weight of titanium dioxide.

In addition, the present invention to achieve another technical problem,

(a) thermosetting the titanium dioxide at 400 to 600 ° C. to adjust the crystallinity to be 10 to 20% as measured by X-ray diffraction;

(b) impregnating the aqueous solution of vanadium precursor to the titanium dioxide prepared in step (a);

(c) drying the resultant of step (b) at 100 to 300 ° C. and calcining at 400 to 600 ° C. for 1 to 5 hours; And

(d) providing a catalyst for the decomposition of toxic contaminants comprising coating the result of step (c) on the cordialite surface with alumina.

According to an embodiment of the present invention, prior to performing the step (b), an aqueous solution of a precursor of one or more metals selected from molybdenum (Mo), tungsten (W), palladium (Pd), and oxides thereof (a It is preferable to further include a step of impregnating the result of the step) and drying and firing the resultant at 100 to 300 ℃.

In addition, the present invention decomposes polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), polychlorinated biphenyl (PCB) and chlorobenzene, chlorine-based volatile compounds and nitrogen oxides using the catalyst. Provide a way to.

According to an embodiment of the present invention, the decomposition reaction is preferably carried out under an atmosphere of maintaining an oxygen concentration of 5% by volume to 21% by volume.

According to an embodiment of the present invention, the decomposition reaction is preferably carried out at 200 ℃ to 350 ℃.

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

Supported catalysts in the form of metals or metal oxides supported on other porous metal oxides generally promote catalysis by the interaction of a porous support or carrier with the metal or metal oxide, Porous oxides are used as carriers to enhance thermal stability. In other words, it is important to increase the reaction activity of the catalyst by providing a thin surface of the catalyst metal in a porous material having a large surface area and excellent thermal and mechanical stability.

At this time, the type and content of the metal component used, the composition ratio of the metal component is an important factor of the catalytic efficiency. In addition, the type and composition of the carrier is also an important factor influencing the catalyst efficiency because it interacts with the metal components and greatly affects the catalyst performance.

In the present invention, considering the factors as described above, titanium dioxide (TiO ₂ ) or titanium dioxide (TiO ₂ ) -alumina (Al ₂ O ₃ ) is used as a carrier on a cordierite surface that provides a honeycomb shape. In addition, vanadium is basically used as a metal component.

Titanium dioxide (TiO ₂ ) is an oxide that can be partially reduced, and is known to not only disperse active metal components well, but also to have high thermal stability and to strongly interact with metals. In addition, depending on the conditions of the reduction treatment, the + 3-valent and + 2-valent states are possible, and there is a characteristic that shows strong metal-carrier interaction after reduction treatment.

In addition, alumina used in the present invention is a metal oxide having a large surface area and is a porous material having excellent mechanical stability.

That is, the present invention increases the thermal and mechanical stability by using titanium dioxide (TiO ₂ ) or titanium dioxide (TiO ₂ ) -alumina (Al ₂ O ₃ ) as a support on the cordierite surface providing a honeycomb shape, By appropriately adjusting the crystallinity of the surface to maximize the surface area, the active metal particles are dispersed well, so that the sintering of the metal particles does not occur at the use temperature and the decomposition of the exhaust gas is high.

Therefore, the honeycomb cordialite-titanium dioxide (TiO ₂ ) or cordialite-titanium dioxide (TiO ₂ ) -alumina (Al ₂ O ₃ ) used as a carrier in the catalyst for decomposition of toxic pollutants according to the present invention is It provides a large surface area and thermal and mechanical stability, acid resistance and serves to cause strong interaction with the catalyst metal particles, the content is preferably 85 to 99% by weight based on the total weight of the catalyst.

On the other hand, vanadium oxide serves to provide high decomposition activity at low temperatures due to low temperature reducibility, the content is preferably 1 to 6% by weight based on the weight of titanium dioxide.

According to one embodiment of the present invention, in addition to vanadium, which is a metal active component of the catalyst according to the present invention, molybdenum (Mo), tungsten (W), palladium (Pd) or an oxide thereof may be added. Stabilization of the vanadium, improves the dispersion degree and serves to improve the efficiency, the content is preferably 0 to 9% by weight based on the weight of titanium dioxide.

In particular, palladium provides an active site exhibiting high activity in the decomposition of toxic compounds by strong interaction with vanadium, the content of which is preferably 0 to 1% by weight based on the weight of titanium dioxide.

The catalyst according to the present invention may be prepared by a method generally used in the art to prepare a metal supported catalyst. Specifically, the catalyst according to the present invention is preferably prepared in the following process sequence.

(a) thermally calcining titanium dioxide at 400 to 600 ° C. to adjust the crystallinity to be 20% or less as measured by X-ray diffraction;

(b) impregnating the aqueous solution of vanadium precursor to the titanium dioxide prepared in step (a);

(c) drying the resultant of step (b) at 100 to 300 ° C. and calcining at 400 to 600 ° C. for 1 to 5 hours; And

(d) providing a catalyst for the decomposition of toxic contaminants comprising coating the result of step (c) on the cordialite surface with alumina.

If one or more metals selected from molybdenum (Mo), tungsten (W), palladium (Pd) and their oxides are to be added, their precursor aqueous solution is impregnated with titanium dioxide prior to step (b). Preferably, the result may further comprise the step of drying and firing at 100 to 300 ℃.

The catalysts according to the invention are particularly suitable for decomposing polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), polychlorinated biphenyl (PCB) and chlorobenzene, chlorine-based volatile compounds and nitrogen oxides. Particularly useful.

According to an embodiment of the present invention, in the method for treating the combustion process exhaust gas using the catalyst according to the present invention, the decomposition reaction is preferably carried out under an atmosphere of maintaining an oxygen concentration of 5% by volume to 21% by volume. .

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

<Manufacture example 1>

300 g of titanium dioxide was calcined at 550 ° C. for 3 hours to adjust the crystallinity so that the crystallinity measured by X-ray diffraction method was 10-20%. The resulting product was loaded with 24 g of molybdenum (Mo) oxide, dried at 110 ° C. for 5 hours, and calcined at 550 ° C. for 2 hours. The resultant was loaded with 17 g of vanadium (V) oxide and dried and calcined under the same conditions as described above.

The honeycomb type cordialite surface was coated to carry 50g of the resultant and 20g of alumina per 1000 cm ³ of cordialite. The resultant was dried at 110 ° C. for 5 hours and finally calcined at 550 ° C. for 2 hours to form honeycomb cordierite-titanium dioxide (TiO ₂ ) -alumina (Al ₂ O ₃ ) -vanadium (V) oxide-molybdenum. A denium (Mo) oxide catalyst was prepared.

<Manufacture example 2-4>

Cordialite-titanium dioxide (TiO ₂ ) -alumina (Al ₂ O ₃ ) -vanadium in the same manner as in Preparation Example 1, except that tungsten (W) oxide and palladium (Pd) oxide were used instead of molybdenum. (V) Oxide-tungsten (W) oxide catalyst (Production Example 2), Cordialite-Titanium Dioxide (TiO ₂ ) -Alumina (Al ₂ O ₃ ) -Vanadium (V) oxide-Palladium (Pd) Catalyst (Production Example 3) was prepared.

<Example 1>

To test the exhaust gas purification rate of a commercial municipal waste incinerator, cordialite-titanium dioxide (TiO ₂ )-alumina (Al ₂ O ₃ )-vanadium (V) oxide, 15 cm in diameter, 15 cm in width and 30 cm in length Table 1 shows the results of measuring the decomposition rate of dioxins and nitrogen oxides while varying the reaction temperature and space velocity using a molybdenum (Mo) oxide catalyst (Preparation Example 1).

No. Reaction temperature (℃) Space velocity (hr ^-1 ) Reactor Outlet Dioxin Concentration (ng TEQ / Nm ³ ) Dioxin degradation rate (%) NO _x decomposition rate (%) 1-11-21-31-41-51-6 250 250 300 300 350 350 7,00010,0007,00015,0007,00010,000 0.0180.070.0090.1560.0210.032 88.948.292.680.595.593.5 --91.184.499.995.9

In Table 1, TEQ means a toxic equivalent. Since the name dioxin contains more than two hundred substances, total toxicity is indicated by multiplying the concentration by the concentration of the toxic equivalence factor (TEF) of each substance.

<Example 2>

Using the catalyst of Preparation Example 1, a cordierite-titanium dioxide (TiO ₂ )-alumina (Al ₂ O ₃ )-vanadium (V) oxide-molybdenum (Mo) oxide catalyst of 2.54 cm in diameter, 5 cm in length , By varying the reaction temperature and space velocity, the decomposition rate was measured under conditions of 100 ppm 1,2-dichlorobenzene and 5 vol% H ₂ O, 11 vol% O ₂ and the results are shown in Table 2.

No. Space velocity (hr ^-1 ) Reaction temperature (℃) Decomposition rate (%) 2-12-22-33-42-52-62-72-82-92-102-11 5,7005,7005,7005,7005,7007,0007,0007,0008,6008,6008,600 250 300 350 380 400 350 380 400 350 380 400 63.158.578.490.497.259.386.394.356.179.490.2

<Example 3>

It was carried out using the catalyst of Preparation Example 2, cordierite-titanium dioxide (TiO ₂ ) -alumina (Al ₂ O ₃ ) -vanadium (V) oxide-tungsten (W) oxide catalyst having a diameter of 2.54 cm and a length of 5 cm. The decomposition rate was measured while changing only the reaction temperature under the reaction conditions of Example 2, and the results are shown in Table 3.

No. Space velocity (hr ^-1 ) Reaction temperature (℃) Decomposition rate (%) 3-13-23-33-43-5 5,7005,7005,7005,7005,700 250300350380400 60.661.462.068.670.6

<Example 4>

Example 2 using the catalyst of Preparation Example 3, cordierite-titanium dioxide (TiO ₂ ) -alumina (Al ₂ O ₃ ) -Vanadium (V) oxide-palladium (Pd) catalyst of diameter 2.54 cm, length 5 cm In the reaction conditions of, the decomposition rate was measured while changing the space velocity and the reaction temperature is shown in Table 4.

No. Space velocity (hr ^-1 ) Reaction temperature (℃) Decomposition rate (%) 4-14-24-34-44-54-64-74-8 5,7005,7005,7005,7005,7007,0007,0007,000 250 300 350 380 400 350 380 400 55.086.098.099.099.955.985.794.1

From the above results, it can be seen that the decomposition rate of dioxins, nitrogen oxides (NO _x ), and chlorobenzenes of the catalyst for decomposition of toxic contaminants of the present invention is very high, and thus has a suitable performance as an exhaust gas purification catalyst.

Vanidium (V), vanadium (V), molybdenum (Mo), or palladium (Pd) in a honeycomb carrier of cordialite-titanium dioxide (TiO ₂ ) -alumina (Al ₂ O ₃ ) component according to the present invention Or catalysts bearing oxides thereof have a high activity in the decomposition of toxic pollutants including dioxins, nitrogen oxides (NO _x ) and chlorobenzenes, and thus chlorine compounds such as dioxins contained in exhaust gases emitted in various combustion processes. It can be usefully used for the decomposition of toxic contaminants including and nitrogen oxides.

Claims (11)

Cordialite-titanium dioxide-alumina carrier coated with 6-12 wt% titanium dioxide (TiO ₂ ) and 10-30 wt% alumina (Al ₂ O ₃ ) based on the total weight of the catalyst on the cordialite surface X-ray diffraction method is carried on the surface of titanium dioxide with 1 to 6% by weight of vanadium (V) and 1 to 9% by weight of molybdenum (Mo) or molybdenum oxide as catalytically active components. The catalyst for the decomposition of chlorine compounds and / or nitrogen oxides, characterized in that the crystallinity of the titanium dioxide measured by 10 to 20%. delete delete delete delete delete (a) thermally calcining titanium dioxide at 400 to 600 ° C. to adjust the crystallinity to be 20% or less as measured by X-ray diffraction; (b) impregnating the aqueous solution of vanadium precursor to the titanium dioxide prepared in step (a); (c) drying the resultant of step (b) at 100 to 300 ° C. and calcining at 400 to 600 ° C. for 1 to 5 hours; And (d) coating the resultant of step (c) with the alumina on the cordialite surface; a method for preparing a catalyst for decomposing chlorine-based compounds and / or nitrogen oxides according to claim 1. The method of claim 8, wherein before the step (b) is performed, an aqueous solution of a precursor of at least one metal selected from molybdenum (Mo), tungsten (W), palladium (Pd) and oxides thereof is used. Impregnating the resulting product and drying and firing the resulting product at 100 to 300 ° C. Polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), polychlorinated biphenyl (PCB) and chlorobenzene, chlorine-based volatile compounds using the catalyst according to any one of claims 1 to 7. To decompose nitrogen oxides. 10. The process according to claim 9, which is carried out in an atmosphere which maintains an oxygen concentration of 5% by volume to 21% by volume. 10. The process according to claim 9, wherein the decomposition reaction is carried out at 200 ° C to 350 ° C.