KR20160075928A - Fe-Cr/C complex catalyst for simultaneous removing NOx and SOx and fabrication method thereof - Google Patents

Abstract

The present invention relates to a Fe-Cr/C composite catalyst for simultaneously removing NOx and SOx and a method for preparing the same. More particularly, the present invention relates to a Fe-Cr/C composite catalyst in which a carbon support contains a certain content ratio of Fe and Cr to allow NOx and SOx in exhaust gas to be simultaneously removed through a selective catalyst reduction method (SCR) and an adsorption method, and to a method for preparing the composite catalyst. The Fe-Cr/C composite catalyst is advantageous in that the SCR reaction can be performed at relatively low temperature; NOx and SOx can be simultaneously treated at a high removing rate; and reuse is available after post-processing. Also, the operation temperature of the SCR process can be lowered and a risk of ignition can be reduced.

Description

The present invention relates to a Fe-Cr / C composite catalyst for simultaneous removal of NOx and SOx,

The present invention relates to an Fe-Cr / C composite catalyst capable of simultaneously removing NOx and SOx in exhaust gas and a method for producing the same.

Nitrogen oxides (hereinafter "NOx") and sulfur oxides (hereinafter referred to as "SOx") emitted from the combustion process of fossil fuels are known to be major causes of acid rain, respiratory diseases and photochemical smog. These air pollutants are increasingly being regulated in Korea as well as in foreign countries due to the growing interest in environmental issues.

SOx is emitted from facilities that mainly burn coal or heavy oil such as thermal power plants, steel mills, and small- and medium-sized boilers. Accordingly, a number of technologies such as a wet lime-gypsum process, an activated carbon process, and a dry or semi-dry absorbent technology have been put into practical use as fuel gas desulfurization (FGD) for removing sulfur oxides from exhaust gas.

NOx is largely classified into fuel NOx (fuel NOx) due to oxidation of nitrogen components in fuel and high-temperature NOx (thermal NOx), which is inevitably generated at high temperatures such as a combustion process.

Among the technologies known as NOx removal are selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR), of which the selective catalytic reduction (SCR) is the most widely used.

The SCR process converts NOx to nitrogen and water by reacting with ammonia or urea injected as a reducing agent on the catalyst. At this time, attempts have been made to improve the removal efficiency of nitrogen oxides by variously changing the catalyst.

It has been reported that the catalyst mainly used in the selective catalytic reduction is a V ₂ O ₅ -WO ₃ -TiO ₂ catalyst and can remove up to 90% or more of NO x according to reaction conditions (Chemical Engineering Progress (1994) pp.39- 45).

In addition, Korean Patent Laid-Open Publication No. 2005-0064506 proposes a manganese-supported carbon catalyst for NOx removal, and 2005-0064235 suggests a sulfuric acid-treated carbon catalyst.

On the other hand, these conventional technologies (individual desulfurization technology + denitrification technology) are performed through two processes, desulfurization and denitrification, which are completely different in character from a large amount of flue gas. For example, technologies developed to improve the disadvantages of individual desulfurization processes and denitrification processes include simultaneous desulfurization / denitrification techniques using electron beams, non-thermal plasma, activated carbon, etc. have.

Korean Patent Publication No. 1999-0033785 discloses flue gas desulfurization using an electron beam. 2002-0012379 discloses a desulfurization and denitration treatment apparatus having a reactor for causing SOx and NOx in the exhaust gas to react with ozone, and Japanese Patent Application No. 2010-0104926 discloses an apparatus for treating exhaust gas And a reactor for connecting the plasma reactor and the SCR reactor to the apparatus for denitrification.

In addition, the electron beam process, the ozone process device, and the plasma process are different from each other in terms of optimum operating conditions, and the initial investment cost and the operating cost increase due to the process must be individually installed, and the optimum process combination method is pointed out as a big problem. Further, as there is a difficulty in collecting the occurrence of fine salt and the other is that NO is easily oxidized, while NO ₂ is not rapidly react with the NH ₃ low and the overall NOx reduction ratio to NO _2.

In addition, a technology for simultaneously performing desulfurization / denitrification using activated carbon has been proposed. This technology was developed by Bergbau Forschung, a research institute related to the coal industry in Germany. It is a process that uses activated carbon as SOx adsorbent and SCR catalyst. However, these technologies have a disadvantage in that the desulfurization efficiency is high but the denitrification efficiency is somewhat low (about 40 to 70%) as compared with the facility investment cost.

Japanese Patent Laid-Open Nos. 1993-105415 and 2001-294414 also disclose a method for producing simultaneous desulfurization and denitrification activated coke. However, it is known that the denitrification performance of the activated coke catalyst is poor in the presence of SOx [K. The desulfurization rate is 90% or more, but the denitration rate is only about 20 to 30% in the case of a facility operated in Nippon Steel.

Korean Patent Publication No. 1999-0033785 Korean Patent Publication No. 2002-0012379 Korean Patent Publication No. 2010-0104926 Japanese Patent Laid-Open No. 1993-105415 Japanese Patent Laid-Open No. 2001-294414

In order to solve the above-mentioned problems, Applicants have conducted various studies to simultaneously achieve NOx and SOx, and to secure a high removal efficiency. As a result, Fe and Cr were selected as specific transition metals to be supported on a carbon support, And that the composite catalyst can effectively remove NOx and SOx, thereby completing the present invention.

Accordingly, an object of the present invention is to provide an Fe-Cr / C composite catalyst capable of simultaneously treating NOx and SOx, and a method for producing the same.

In order to achieve the above object, the present invention provides an Fe-Cr / C composite catalyst in which Fe and Cr are supported in a carbon support in order to simultaneously remove nitrogen oxides and sulfur oxides in exhaust gas through an ammonia reduction reaction and an adsorption reaction to provide.

The carbon support may be activated carbon, carbon fiber, activated coke, carbon black, carbon nanotube, fullerene or graphene.

The carbon support has a specific surface area of 100 to 3,000 m ² / g and a pore size of 1 nm to 100 μm.

In particular, the Fe-Cr / C composite catalyst is supported on the carbon support in an amount of 0.05 to 2.0% by weight of Fe and 0.05 to 2.0% by weight of Cr, wherein the content of Fe and Cr is 1: 0.2 to 1: 4, preferably in a weight ratio of 1: 0.5 to 1: 2.

The present invention also relates to a method for preparing a precursor solution, comprising the steps of: mixing Fe and Cr precursor solution;

Immersing the carbon support in the precursor solution;

Drying; And

And then heat-treating the Fe-Cr / C composite catalyst in an inert atmosphere.

The Fe precursor may be one selected from the group consisting of FeSO ₄ , Fe ₂ (SO ₄ ) ₃ , Fe (NO ₃ ), FeCl ₃ , Fe (OCH ₃ ) ₃ , .

The Cr precursor may be one selected from the group consisting of Cr (NO ₃ ) ₂ , CrCl, CrCl ₂ , CrCl ₃ , Cr (OH ₂ ), and combinations thereof.

In addition, the heat treatment is performed at 350 to 500 ° C.

The Fe-Cr / C composite catalyst according to the present invention has the effect of simultaneously removing NOx and SOx by selective catalytic reduction (SCR) and adsorption.

The Fe-Cr / C composite catalyst enables the SCR reaction to be performed at a low temperature, so that it is unnecessary to heat the exhaust gas at a high temperature for the conventional SCR reaction, thereby reducing the overall processing cost.

In addition, the Fe-Cr / C composite catalyst used has the advantage of being reusable through simple treatment.

FIG. 1 is a flow chart showing steps of producing the Fe-Cr / C composite catalyst proposed in the present invention.
2 is a schematic diagram of an apparatus for removing NOx and SOx used in Experimental Example 1. FIG.

The present invention provides a composite catalyst capable of simultaneously removing nitrogen oxides (NO _x ) and sulfur oxides (SO _x ) in the exhaust gas.

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

NOx and SOx existing in the exhaust gas are removed by various methods. In the present invention, as shown in the following reaction formula 1, NOx is removed by selective catalytic reduction (SCR) using ammonia, and by the adsorption reaction as shown in the following reaction formula Simultaneously remove SOx.

[Reaction Scheme 1]

6NO + 4NH ₃ ? 5N ₂ + 6H ₂ O

4NO + 4NH ₃ + O ₂ ? 4N ₂ + 6H ₂ O

_{6NO 2 + 8NH 3 → 7N 2} + 12H 2 O

_{2NO 2 + 4NH 3 + O 2} → 3N 2 + 6H 2 O

[Reaction Scheme 2]

SO₂   → SO₂ (ad)

SO ₂ (ad) + O ₂ (ad)? SO ₃ (ad)

SO _{3 (ad) + H 2 O (} ad) → H 2 SO 4 (ad)

The complex catalyst proposed in the present invention is a Fe-Cr / C composite catalyst having a structure in which Fe and Cr are simultaneously carried in a carbon support.

Denitrification and desulfurization occur due to the carbon support, and the transition metals Fe and Cr carried thereon accelerate the reaction rates of the above-mentioned Reaction Schemes 1 and 2, thereby further promoting the SCR reaction. This composite catalyst has an advantage of increasing the denitration efficiency by about 1.5 times or more as compared with the case where Fe or Cr is supported on the carbon support, respectively. In particular, there are techniques in which various metals or noble metals are supported on a carbon support, but the combination of Fe and Cr is the most excellent.

The selection of the catalyst should be based not only on the activity of the reaction but also on the catalyst poison and price. In the case of Fe, the activity is excellent in the SCR reaction. In addition, Cr is active in the SCR reaction, It is also effective for the decomposition of chlorinated compounds, and an excellent effect of mixing can be expected even under the condition of SOx. Apart from this, the application of precious metals such as Pt is not easy due to cost problems.

Specifically, the promotion of denitrification and desulfurization reaction can be appropriately controlled by controlling the content and content ratio of Fe and Cr carried in the Fe-Cr / C composite catalyst.

At this time, Fe is supported in the carbon support (C) at 0.05 to 2.0 wt%, more preferably 0.3 to 1.0 wt%. If the amount of Fe supported is less than the above range, the reaction is not promoted sufficiently and the denitrification and desulfurization efficiency are lowered. On the other hand, if the amount is exceeded in the above range, Fe itself becomes a ignition point, do.

Also, Cr is supported in the carbon support in an amount of 0.05 to 2.0 wt%, more preferably 0.3 to 1.0 wt%. If the amount of Cr supported is less than the above range, the promotion of the reaction is insufficient and the denitrification efficiency is lowered. On the contrary, if the Cr amount exceeds the above range, there is a risk of ignition.

In addition, the total content of Fe and Cr carried in the Fe-Cr / C composite catalyst is used in the range of 0.1 to 4.0% by weight, more preferably 0.5 to 2.0% by weight in the carbon support (C).

The supported Fe and Cr are mixed in a weight ratio of 1: 0.2 to 1: 4, preferably 1: 0.5 to 1: 2, most preferably 1: 0.6. Such a content range is a content range for ensuring the maximum effect of Fe and Cr, and the efficiency is lowered when it is out of the above range. Therefore, the content range is suitably used within the above range.

These Fe and Cr are carried in the carbon support as mentioned above.

The carbon support used in the present invention has a catalytic effect on denitrification and desulfurization as well as a role of sufficiently supporting Fe and Cr. Such a support can further increase denitrification and desulfurization rates compared to other materials (e.g., zeolite, etc.).

The carbon support is not particularly limited in the present invention, and materials known in the art may be used. Preferably, it may be activated carbon, carbon fiber, activated coke, carbon black, carbon nanotubes, fullerene or graphene, preferably an activated coke may be used.

Particularly, in order to further increase the catalytic effect of desulfurization and denitration, the carbon support has a limited particle size and specific surface area.

Preferably, the carbon support has a specific surface area of 100 to 3,000 m ² / g, and the pores may be mesopores, nano pores, macropores, etc. Preferably, the pores have a pore size of 1 nm to 100 μm Is used. If the specific surface area is less than the above range, sufficient catalytic activity as an exhaust gas treating catalyst can not be obtained due to a low specific surface area. On the other hand, when the specific surface area exceeds the above range, the pore size is relatively decreased. Since Cr can not be effectively supported, it is suitably used within the above range.

In this case, the Fe-Cr / C composite catalyst may further contain a known transition metal or a noble metal, which is used in an amount of 0.1 wt% or less in the carbon support. The transition metals and noble metals that can be used are one species selected from the group consisting of manganese, cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, iridium, platinum, gold and combinations thereof.

The above-described Fe-Cr / C composite catalyst according to the present invention can be produced through an immersion method using a precursor.

Specifically, as shown in Fig. 1,

(S1) mixing Fe and Cr precursor solution;

(S2) immersing the carbon support in the precursor solution;

(S3) drying; And

(S4) heat treatment in an inert atmosphere.

Each step will be described in detail below.

First, Fe and Cr precursors to be supported on a carbon support are selected and mixed to prepare a precursor mixed solution (S1).

The precursor may be a substance capable of providing a metal through heat treatment, and may be a sulfate, a nitrate, a hydrochloride, an acetate salt, an alkoxide, and a hydroxide including Fe or Cr.

Preferably a, Fe precursors include _{FeSO 4, Fe 2 (SO 4} ) 3, Fe (NO 3), FeCl 3, Fe (OCH 3) 3, and from the group consisting of a selected one member can be, and preferably In the following, FeSO ₄ , Fe (NO ₃ ), and more preferably, the amount of ammonia used as a reducing agent is further increased to increase denitrification and desulfurization efficiency, and FeSO ₄ is used.

In addition, Cr precursor is the Cr (NO _{3) 2,} CrCl, CrCl _2, CrCl _3, Cr (OH) _2, and the Cr decided from the group consisting of a selected one member can be, and preferably (NO _{3) 2} use.

The use of these precursors can be used in consideration of the loading amounts of Fe and Cr present in the final Fe-Cr / C composite catalyst.

The precursor solution is prepared by dissolving in a solvent, and the solvent is not particularly limited in the present invention, and any solvent that can stably dissolve the metal salt can be used. For example, water, methanol, ethanol, ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 3-methoxymethylbutanol, N-methylpyrrolidone, terpineol alone, Mixed solvents may be used.

Next, a step of immersing the carbon support in the precursor mixture solution is performed (S2).

Through the immersion, the Fe and Cr precursors are adsorbed to the pores in the carbon support, and stirring or heating may be performed to increase the degree of adsorption.

The stirring or heating may be appropriately selected by a person skilled in the art, and the heating temperature may be appropriately selected by a commonly used solvent.

Next, a step of removing the solvent through drying is performed (S3).

The drying may be performed at a temperature at which the solvent can be sufficiently removed, usually at a level of 30 to 150 캜, and is not particularly limited in the present invention.

Next, the Fe-Cr / C composite catalyst is prepared by performing heat treatment in an inert atmosphere (S4).

The organic salt portion of the precursor is removed through the heat treatment to obtain a composite catalyst having a structure in which only Fe and Cr are adsorbed (i.e., supported) in the pores of the carbon support.

At this time, if oxygen is present during the heat treatment, it is preferable to perform the heat treatment in an inert atmosphere because there is a risk of ignition during the heat treatment. This inert atmosphere can be achieved by injecting nitrogen, argon or a mixture thereof, preferably with nitrogen.

In addition, heating is performed to sufficiently remove the organic composition (precursor, solvent, etc.) in the solution, and the heat treatment is performed at 300 to 500 ° C, preferably 350 to 450 ° C for 30 minutes to 10 hours. If the temperature is less than the above range, it is difficult to sufficiently remove the organic composition, resulting in deterioration of catalytic activity. On the contrary, when the temperature is in the above range, Fe and Cr may not be uniformly distributed in the carbon support. Perform properly within the range.

The Fe-Cr / C composite catalyst obtained through the above-described steps has the effect of simultaneously removing NOx and SOx in the exhaust gas as mentioned above. The Fe-Cr / C composite catalyst may be formed into various shapes so as to maximize the effects and to be applicable to various devices.

The molding may be carried out before or after the heat treatment.

As an example, a method of coating a precursor mixture solution on a support followed by drying and heat treatment; A method in which particles obtained after drying are injected into a molding die and molded into a specific shape and then subjected to heat treatment; A method in which the particles obtained after the heat treatment are finely pulverized to obtain powders of a predetermined size, and then the forming is performed.

The method is not particularly limited in the present invention, and any of the methods used in the field of the catalyst forming technology can be used.

Preferably, a method of molding the pulverized powder can be considered. The fine pulverized powder may be spherical particles of 1 to 50 탆 using a known pulverizer, for example, a ball miller or the like. The pulverized powder may be formed into a block shape through a process such as compression molding and then introduced into various exhaust gas processing apparatuses have.

In the exhaust gas treatment device, the Fe-Cr / C composite catalyst is put in powder form instead of the desulfurizing agent, and when the oxidizing device is combined, atmospheric pollutants can be treated simultaneously without any large facility investment.

In particular, as can be seen from the results of Experimental Example 1, the Fe-Cr / C composite catalyst according to the present invention shows a NOx removal rate of 56% or more and a SOx removal rate of 100% at 150 ° C, It was possible to confirm the cracking.

Most of the SCR catalysts exhibit the activity of the catalyst at a high temperature of 250 to 400 캜, and a very low removal rate is generally exhibited at a low temperature of 200 캜 or lower. As a result, the SCR reaction must be carried out at a high temperature in order to maintain the catalytic activity.

However, from the above results, it is possible to place the SCR device at the rear end of a particulate matter removal device such as an electrostatic precipitator if it can be operated in a low temperature region (<200 ° C). As a result, there is an advantage that the poisoning phenomenon of the catalyst is prevented and a process such as exhaust gas reheating is unnecessary.

The used Fe-Cr / C composite catalyst can be regenerated through heat treatment at a temperature of 300 to 500 ° C. in an inert atmosphere, and the regenerated Fe-Cr / C composite catalyst can be reused.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to further illustrate the present invention, and the scope of the present invention is not limited by the following examples. The following examples can be appropriately modified and changed by those skilled in the art within the scope of the present invention.

Example  One: Fe - Cr / C composite catalyst 1

The activated coke catalyst used in the new Japanese steel mill was used as a carbon carrier (BET surface area 2500 m ² / g, average pore size 15 nm).

A FeSO ₄ aqueous solution (1.5%, 300 mL) and a Cr (NO ₃ ) ₂ aqueous solution (1.2%, 300 mL) were mixed as a precursor in the reactor, and 300 g of the carbon carrier was immersed therein for 2 hours.

Subsequently, the catalyst was dried at 100 ° C. for 1 hour, and then heat-treated at 400 ° C. for 3 hours in a nitrogen atmosphere to prepare an Fe-Cr / C composite catalyst.

The supported amount of Fe-Cr / C composite catalyst was measured by ICP-AES (inductively coupled plasma-atomic emission spectrometer), and was measured as Fe 0.5 wt% and Cr 0.3 wt%.

Example  2: Fe - Cr / C composite catalyst 2

Cr / C composite catalyst was prepared in the same manner as in Example 1 except that Fe (NO ₃ ) ₂ was used instead of FeSO ₄ as an Fe precursor.

Comparative Example  One: Fe / C composite catalyst

The Fe / C composite catalyst was prepared in the same manner as in Example 1 except that 1.0 wt% of Fe was supported using FeSO ₄ alone as a precursor.

Comparative Example  2: Cr / C composite catalyst

The procedure of Example 1 was repeated except that Cr / C composite catalyst supporting 1.0 wt% Cr was prepared using FeSO ₄ alone as a precursor.

Comparative Example  3: Fe - Cr / C composite catalyst 3

The Fe-Cr / C composite catalyst was prepared in the same manner as in Example 1, except that the content ratio of Fe and Cr was 1: 0.1 and the sum of the contents of Fe and Cr was 0.05 wt% in the carbon support.

Comparative Example  4: Fe - Cr / C composite catalyst 3

The Fe-Cr / C composite catalyst was prepared in the same manner as in Example 1 except that the content ratio of Fe and Cr was 1: 5, and the sum of the Fe and Cr contents was 6.0 wt% in the carbon support.

Comparative Example  5: Fe - Cr / Preparation of zeolite complex catalyst

The Fe-Cr / zeolite composite catalyst was prepared in the same manner as in Example 1 except that zeolite was used as a support.

Experimental Example  One: NOx  Measurement of removal efficiency

(1) Experimental apparatus

The apparatus for removing NOx and SOx was composed of a gas injection unit, a catalytic reactor, and a gas measuring device as shown in FIG.

The gases used were NO (200 ppm, N ₂ balance), SO ₂ (200 ppm, N ₂ balance), NH ₃ (300 ppm, N ₂ balance), O ₂ (15%), and H ₂ O The gas flow rate was controlled using a mass flow controller (MFC, ModelGMC 1,000 & Brooks 5850E).

The water vapor pressure and N ₂ gas injection flow rate were controlled to inject water into the reactor. Water was condensed and removed in a condenser using a circulation tank (RW-1025G, Lab companion) and an aqueous 5 ° C ethanol solution to selectively remove moisture at the front of the analyzer.

The total experimental equipment temperature was kept constant using heating tape and PID controller.

The reactor containing the catalyst of Examples or Comparative Examples was made of SUS having an inner diameter of 50 mm and a height of 130 mm, and the reaction temperature of the catalyst and the injected gas was controlled by inserting a temperature controller inside the reactor.

At this time, the reaction gas was analyzed by using FT-IR (BIO RED) and chemical cell type analyzer (MK2) at the same time, and the analysis results between the two analyzers were confirmed to be within 5%.

(2) Measurement method

200 ppm of NO, 200 ppm of SO ₂ , 300 ppm of NH ₃ , 15% of O _{2 and} 10% of H ₂ O were mixed in a nitrogen gas. In this experiment, the reaction temperature was changed and the space velocity (gas flow rate / catalyst volume) of the reactor was 1,000 hr ^-1 .

(3) Experimental results

To measure the NOx removal rate and SOx (i.e., SO ₂₎ removal rate according to the temperature shown in Table 1. Only active coke was used as Control Example 1.

NOx removal rate (%) SO2 removal rate (%) 100 ℃ 130 ℃ 150 ℃ Example 1 38 52 56 100% Example 2 24 36 42 100% Comparative Example 1 18 27 34 100% Comparative Example 2 21 29 36 100% Comparative Example 3 17 20 25 88% Comparative Example 4 19 29 32 87% Comparative Example 5 17 28 30 85% Control Example 1 15 19 22 80%

Referring to Table 1, is SO ₂ showed a removal rate of 100%, the removal ratio of NOx was more than 24% of the minimum 100 ℃, exhibited a maximum value more than 56% in 150 ℃.

However, from the above results, the composite catalyst of the present invention showed NOx removal rate of 56% or more and SO ₂ removal rate of 100% even at 150 ° C., and it is not necessary to heat the catalyst to 250 ° C. or more for high removal rate, It is confirmed that the SCR reaction device can be implemented at a low temperature.

The Fe-Cr / C composite catalyst proposed in the present invention is applicable to an exhaust gas treatment apparatus for denitrification.

Claims (11)

In a catalyst used for simultaneously removing nitrogen oxides (NOx) and sulfur oxides (SOx) in an exhaust gas,
Cr / C composite catalyst characterized in that Fe and Cr are supported in a carbon support. The method according to claim 1,
Wherein the carbon support is activated carbon, carbon fiber, activated coke, carbon black, activated carbon, carbon nanotube, carbon fiber, fullerene or graphene. The method according to claim 1,
Wherein the carbon support has a specific surface area of 100 to 3,000 m ² / g and a pore size of 1 nm to 100 μm. The method according to claim 1,
The Fe-Cr / C composite catalyst according to claim 1, wherein the Fe and Cr are supported in a content of 0.1 to 4.0% by weight in the carbon support. The method according to claim 1,
The Fe-Cr / C composite catalyst according to claim 1, wherein the Fe is supported in an amount of 0.05 to 2.0 wt% in the carbon support. The method according to claim 1,
Wherein the Cr is supported in an amount of 0.05 to 2.0 wt% in the carbon support. The method according to claim 1,
The Fe-Cr / C composite catalyst is characterized in that Fe and Cr are supported at a weight ratio of 1: 2 to 1: 4. Mixing Fe and Cr precursor solution;
Immersing the carbon support in the precursor solution;
Drying; And
The method for producing a Fe-Cr / C composite catalyst according to claim 1, wherein the Fe-Cr / C composite catalyst is produced through a heat treatment in an inert atmosphere. The method of claim 8,
The Fe precursor _{FeSO 4, Fe 2 (SO 4} ) 3, Fe (NO 3), FeCl 3, Fe (OCH 3) 3, and Fe, characterized in that it comprises one member selected from the group consisting of -Cr / C composite catalyst. The method of claim 8,
Wherein the Cr precursor includes one selected from the group consisting of Cr (NO ₃ ) ₂ , CrCl, CrCl ₂ , CrCl ₃ , Cr (OH ₂ ), and combinations thereof. Gt; The method of claim 8,
Wherein the heat treatment is performed at 350 to 500 ° C.

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