KR100502852B1 - Cr·W·Ba·TiO2 CATALYST AND METHOD FOR THE REMOVAL OF DIOXINS - Google Patents

Abstract

The present invention relates to a chromium-tungsten-barium-titanium catalyst for dioxin removal and a method for removing dioxin using the same. %, And a dioxin removal catalyst loaded with 1 to 10% by weight of barium, and a dioxin removal method comprising reacting the catalyst with a waste gas containing dioxins under an oxidation atmosphere of 150 ° C. or higher.

By using the chromium-tungsten-barium-titania catalyst for dioxin removal of this invention, the dioxins contained in waste gas can be removed more efficiently.

Description

Chromium, tungsten, barium, titania catalyst for dioxin removal and dioxin removal method using same {Cr, W, Ba, TiO2 CATALYST AND METHOD FOR THE REMOVAL OF DIOXINS}

[TECHNICAL FIELD OF THE INVENTION]

The present invention relates to a chromium-tungsten-barium-titania catalyst for dioxin removal and a dioxin removal method using the same, and more particularly, to a catalyst in which chromium, tungsten, and barium oxide are supported on a titania support, and the catalyst. The present invention relates to a method for removing dioxins contained in waste gas.

[Private Technology]

Dioxin is a generic term for 75 kinds of polychlorinated Dibenzo-p-Dioxins (PCDDs) and 135 kinds of isomers (Polychlorinated Dibenzo Furans, PCDFs). Although they have different properties depending on their number and location, they are commonly referred to as dioxins. Dioxin is a very stable condition that is difficult to break down microorganisms because it is highly soluble and insoluble in water, and its toxicity is practically almost permanent since it is hardly decomposed in nature. Dioxins are therefore known as serious environmental pollutants.

The 210 dioxin isomers mentioned above all have similar physical and chemical properties but differ in their toxicity. Among these, the most toxic compound is 2,3,7,8-TCDD with four chlorine substitutions, and in some countries the most toxic 2,3,7,8- is used to assess the risk of dioxins. Relative toxicity for various types of dioxins is calculated based on TCDD and its value is set as TOF (Toxicity Equivalency Factors). Using this, it is common to express the concentration of dioxins in the concept of Toxic Equivalents (TEQ) as shown in Equation 1.

[Calculation 1]

TEQ = ∑ (density × TEF)

Dioxin's main source of pollution varies from country to country, but can be broadly divided into chemical manufacturing, incineration, and thermal processes. Dioxins can be produced as by-products during the production and use of chlorine organic chemicals, which may contain dioxins. In addition, all thermal processes, including incineration, are important sources of chlorophenol and its derivatives, which can lead to the generation of dioxins.

Therefore, various methods have been developed to remove dioxins contained in waste gases such as incinerators. Representative methods include adsorption and removal of dioxins with an adsorbent such as activated carbon, and decomposition and removal of dioxins by oxidation by a catalyst. Adsorption using activated carbon is a widely used method, but the adsorption capacity is greatly influenced by other components such as water contained in waste gas, and there is a problem in that an adsorbent containing dioxins must be treated after use. Therefore, the oxidation process using a catalyst has been attracting attention as a dioxin removal method.

The complete decomposition method of dioxins using a catalyst is to remove dioxins into CO ₂ and H ₂ O, and HCl or Cl ₂ by oxidizing a gas containing dioxins to the catalyst layer and oxidizing with oxygen present in the waste gas. Way.

In the dioxin removal method using a catalyst as described above, it is very difficult to analyze the dioxin present in the trace gas in the waste gas, so in most cases, chlorobenzene or chloro phenol for the first time to select an appropriate catalyst. For example, it is common to test in a laboratory using simulated reactants that are similar in structure to dioxins or difficult to decompose, such as perchloroethylene, and then apply them to actual dioxins-containing gases. For example, in the well-known document "Chemosphere, Vol. 19, No. 1-6, pp. 361-366, 1989", a catalyst supporting Pt in titania, which shows excellent performance in the decomposition of chlorobenzene, is also used for the removal of dioxins. It has been shown to show good effects, and it is disclosed that chlorobenzene is more difficult to decompose than dioxins.

The catalysts used to remove dioxins by the oxidation method using catalysts generally include many V ₂ O ₅ -WO ₃ -TiO ₂ catalysts used to remove NOx in the waste gas by using a reducing agent such as ammonia. It is used. The publication "Chemosphere, Vol. 26, No. 12, pp. 2167-2172, 1993" uses a V ₂ O ₅ -WO ₃ -TiO ₂ catalyst, which is a catalyst used for NOx removal, in the range of 200 to 350 ° C. It is disclosed that dioxins can be removed. Japanese Patent No. 95-95750 also discloses the removal of dioxins in the range of 200 to 250 ° C using a catalyst consisting of V ₂ O ₅ -WO ₃ -TiO ₂ .

On the other hand, US Patent No. 5,254,794 discloses the removal of dioxins using a catalyst carrying a precious metal such as Pt on a carrier made of TiO ₂ , SiO ₂ , ZrO ₂ , and the like. In addition, Japanese Patent No. 95-163877 and European Patent No. 0,645,172, A1 use catalysts supporting two metals such as Pt and Au on a carrier made of SiO ₂ -B ₂ O ₃ -Al ₂ O ₃ . It is claimed that it is much better than the V ₂ O ₅ -WO ₃ -TiO ₂ catalyst or the catalyst supporting Pt on TiO ₂ .

Therefore, the present invention is cheaper than conventional V ₂ O ₅ -WO ₃ -TiO ₂ catalyst or precious metal supported catalyst, and chromium, tungsten, and barium are supported on a titania support that shows excellent performance in removing dioxins. It is an object to provide a catalyst.

Another object of the present invention is to provide a method for effectively removing dioxins contained in waste gas and the like using a catalyst in which chromium, tungsten, and barium are supported on a titania support.

In order to achieve the above object, the present invention is based on the total weight of the catalyst on the titania support 1 to 30% by weight of chromium, 1 to 40% by weight of tungsten, 1 to 10% by weight of barium dioxin removal chromium- Provided is a tungsten-barium-titania catalyst.

In another aspect, the present invention provides a dioxin removal method characterized in that the waste gas containing the chromium-tungsten-barium-titania catalyst and dioxin in a oxidizing atmosphere of 150 ℃ or more.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention have been studying the method of removing dioxins in the waste gas, and when using a catalyst in which chromium, tungsten, and barium are supported on the titania carrier, the catalyst can be manufactured at low cost, and the removal efficiency of dioxins is also excellent. Discovered and completed the present invention.

The catalyst for removing dioxin of the present invention is chromium-tungsten-supported with 1 to 30% by weight of chromium, 1 to 40% by weight of tungsten and 1 to 10% by weight of barium based on the total weight of the catalyst on the titania support. It is characterized by a barium-titania catalyst.

In the chromium-tungsten-barium-titania catalyst of the present invention, when the content of chromium, tungsten or barium is smaller than the lower limit, the supporting effect of chromium, tungsten or barium is low, and thus the catalytic activity is low, whereas chromium, tungsten or barium If the content exceeds the upper limit, the catalytic activity is rather poor because the content of chromium, tungsten or barium is too high to disperse well on the surface of the catalyst. Preferably the content of the tungsten is 10 to 30% by weight.

When the catalyst is used for dioxin removal, the form of the catalyst is not particularly limited. That is, it may be used in the form of fine powder or pellets, and the catalyst may be coated on a filter or a honeycomb reactor or directly molded into a honeycomb reactor.

The preparation of the catalyst is made through conventional methods of catalyst preparation. For example, when preparing a catalyst in the form of honeycomb, it is directly injection-molded into a honeycomb-type reactor or coated with a honeycomb-type reactor, which is immersed in a solution in which chromium, tungsten and barium are mixed and dissolved in each solution. The catalyst is prepared by soaking in turn, then taken out and dried to allow chromium, tungsten and barium to be supported on the surface of titania. In the case of manufacturing in the form of powder or pellets can be prepared in a similar manner as above.

In another aspect, the present invention provides a dioxin removal method characterized in that the waste gas containing the chromium-tungsten-barium-titania catalyst and dioxin react under an oxidation atmosphere at a temperature of 150 ℃ or more.

The reaction of the chromium-tungsten-barium-titanium catalyst with the dioxin-containing waste gas in the dioxins removal method of the present invention is performed under an oxidation atmosphere of 150 ° C. or higher. Deactivation decreases dioxin removal efficiency. Preferably, the reaction temperature of the chromium-tungsten-barium-titania catalyst and the waste gas containing dioxins is 200 to 450 ° C.

Dioxins contained in the waste gas are decomposed and removed by an oxidation reaction such as the following Formula 1 or 2 by reacting with the chromium-tungsten-barium-titania catalyst of the present invention.

[Formula 1]

[Formula 2]

Hereinafter, examples of the present invention will be described. However, the following examples are intended to illustrate the invention and the present invention is not limited to the following examples.

Example 1 Preparation of Chromium-Tungsten-Barium-Titania Catalyst for Dioxin Removal

Water was added to powdered titania, which is a carrier, and then a colloidal silica was added as a binder to about 10% of the weight of titania to prepare a slurry solution. While mixing the slurry solution, the honeycomb reactor made of cordierite was immersed therein and then taken out so that the titania is coated on the honeycomb surface, and dried in a dryer. The honeycomb reactor coated with titania was immersed in a H ₂ WO ₄ solution dissolved in water, and then taken out and dried to allow tungsten to be supported on the surface of the catalyst and calcined in air at about 450 ° C. The amount of tungsten supported adjusted the concentration of tungsten solution and the number of soaks. In addition, the tungsten-supported honeycomb reactor was again immersed in Cr (NO ₃ ) ₃ .9H ₂ O solution, and then taken out so that chromium was supported. The tungsten and chromium supported catalyst was immersed in Ba (CH ₃ CO ₂ ) ₂ solution so that barium was supported on the catalyst surface. The catalyst was calcined in air at about 450 ° C. to prepare a chromium-tungsten-barium-titanium catalyst.

Example 2 Perchlorethylene Removal Using Chromium-Tungsten-Barium-Titania Catalyst

Using the catalyst prepared in Example 1, the removal rate was measured using perchlorethylene, which is similar in structure to dioxins but more difficult to decompose, as a simulated reactant. The removal rate was measured using a continuous flow reactor at a concentration of 30 ppm perchlorethylene at a reaction temperature of 250 ° C. and an air velocity (flow rate / catalytic reactor volume) of 3,000 hr ⁻¹ , and the results are shown in Table 1 below. Indicated.

TABLE 1

catalyst % Removal Cr content (% by weight) W content (% by weight) Ba content (% by weight) 5 20 One 93 One 40 One 89 30 5 5 94 30 10 5 90 20 10 5 97 20 10 10 88

Example 3

The removal effect of dioxins present in the waste gas was measured using the catalyst prepared in Example 1. The chromium content of the used catalyst was 20% by weight, the tungsten content was 10% by weight, and the barium content was 5% by weight. Dioxin removal rate test was performed using the waste gas discharged from the incinerator, and the removal efficiency was measured after passing the waste gas containing dioxin through the catalyst using a pump. The concentration of dioxin contained in the waste gas was analyzed by using a high resolution gas chromatography / mass spectrometer (GC / MS) after collecting waste gas, purifying and concentrating according to the air pollution process test method. Dioxin removal rate tests were conducted at 260 ° C. and space velocity (gas flow rate / catalytic reactor volume) at 1,900 hr −1 to determine the concentration of each material at the front (inlet) and rear (outlet) of the catalytic reactor.

As a result, the concentration of the front end of the catalytic reactor was 5.07 ngTEQ / Nm ³ , and the concentration of the rear end was 0.48 ngTEQ / Nm ³ . The dioxin decomposition rate is much higher than 70%, which is the dioxin removal rate when a conventional dioxin removal catalyst is used.

As described above, the chromium-tungsten-barium-titania catalyst of the present invention can be produced at low cost, and the chromium-tungsten-barium-titania catalyst of the present invention can be used to more efficiently remove dioxins contained in waste gases. can do.

Claims (4)

A chromium-tungsten-barium-titania catalyst for removing dioxin having 1-30% by weight of chromium, 1-40% by weight of tungsten and 1-10% by weight of barium, based on the total weight of the catalyst on the titania support. The method of claim 1, Chromium-tungsten-barium-titania catalyst for dioxin removal, characterized in that the content of the tungsten is 10 to 30% by weight. A dioxin removal method comprising reacting a chromium-tungsten-barium-titania catalyst of claim 1 or 2 with a waste gas containing dioxins under an oxidizing atmosphere at a temperature of 150 to 450 ° C. The method of claim 3, wherein Reaction temperature of the catalyst and the waste gas is a dioxin removal method, characterized in that 200 to 450 ℃.