KR101629487B1 - Manganese-ceria-tungsten-titania catalyst for removing nox at low temperature and preparing method same - Google Patents

Abstract

A manganese-based catalyst exhibiting excellent nitrogen oxide (NOx) removal activity in a low temperature region of 200 ° C or lower and having durability against hydrogen fluoride, a method for producing the same, and a method for removing nitrogen oxide using the catalyst. The present invention relates to a method for preparing a catalyst for removing nitrogen oxides by supporting an active material containing manganese and ceria on a titania carrier, which comprises the step of adding tungsten to control the oxidation of manganese and ceria Ceria-tungsten-titania catalyst for removing nitrogen oxides.

Description

TECHNICAL FIELD [0001] The present invention relates to a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides at low temperatures, and a method for producing the same. BACKGROUND ART [0002]

More particularly, the present invention relates to a catalyst for removing nitrogen oxides, which exhibits excellent denitration activity in a low temperature region and has durability against hydrogen fluoride, and a method for producing the same.

Recently, NOx (NOx) has been known as the major air pollutant causing the photochemical smog, destruction of the ozone layer and global warming, which occurs in industrial boilers, thermal power plants and waste incineration facilities. Various methods for removing nitrogen oxides have been researched and developed, and selective catalytic reduction (hereinafter referred to as "SCR") is widely used. This SCR is a technique in which ammonia and nitrogen oxide, which are reducing agents, selectively react with each other on the catalyst and decompose into nitrogen and water.

The denitration catalysts applicable to ammonia SCR can be variously manufactured. A variety of catalysts have been proposed, from noble metal catalysts to basic metal catalysts, and it is known that the interaction of the supported active materials with the carrier greatly affects the SCR efficiency.

Specifically, it has been reported that vanadium-tungsten-titania and vanadium-molybdenum-titania catalysts, which are commercial catalysts widely used in recent SCRs, exhibit excellent denitrification efficiency at 300 to 400 ° C. However, there is a problem that SCR reaction is difficult due to low activation energy at a temperature of 200 ° C or lower.

At present, interest in LNG combined cycle power plants is increasing in Korea. When a vanadium-based commercial catalyst is used in the process of applying an SCR process to a conventional LNG power plant, a process of raising the temperature to maintain a temperature of 300 to 400 ° C. is required. Therefore, a catalyst that exhibits excellent efficiency at a low temperature region of 200 ° C or less, which is the temperature of the space where the SCR process can be applied to the LNG power plant, is required.

Also, a low-temperature SCR catalyst is required in a nitrogen oxide treatment process occurring in a semiconductor manufacturing process. In the semiconductor manufacturing process, a variety of noxious gases are generated. Among them, a gas scrubber method is used. Of these, the direct combustion method is a method of treating harmful gas at high temperature by using LPG fuel, showing a high efficiency and treating of perfluoro compounds (PFCs). Perfluorocarbons are used extensively in the semiconductor industry, for example in etching and reactor cleaning stages, and are treated by perfluorocarbon removal catalysts. However, a small amount (several ppm) of perfluorocarbon which is not removed is converted into hydrogen fluoride by reacting with moisture, which has a problem of lowering the SCR catalyst efficiency. Semiconductor manufacturing process Removal of PFCs The temperature of the downstream end of the catalyst is 160 ~ 180 ℃, which requires low-temperature SCR catalyst. Accordingly, there is a demand for a denitration catalyst which exhibits high efficiency at a temperature of 200 DEG C or less and is excellent in durability against hydrogen fluoride.

On the other hand, Non-Patent Document 1 discloses a manganese / ceria / titania catalyst as a catalyst that can be used in a low-temperature region, and studies the nitrogen oxide removal performance and reaction characteristics at low temperature by adding ceria to titania .

A manganese-calcium / titania catalyst is disclosed as a usable catalyst in a low-temperature region, and calcium is added to a manganese / titania catalyst to form a manganese-calcium / titania catalyst. And the specific surface area of the catalyst is increased to study the nitrogen oxide removal performance and the reaction characteristics in the low temperature region.

In addition, Patent Document 1 discloses a method for producing a catalyst composition for removing nitrogen oxides and a method for removing nitrogen oxides from an exhaust gas containing water using the same, more specifically, a method of impregnating activated carbon with a copper nitrate solution, To remove nitrogen oxides.

As described above, the present study on the catalyst for removing nitrogen oxides improves the dispersion degree of manganese, which is an active metal, to enhance the adsorption point (in the case of Non-Patent Document 1 and Patent Document 1) or to improve the oxidation / reduction ability at low temperature (In the case of non-patent document 2). However, in order to prepare a highly active manganese-based catalyst, there is still a lack of research on improving the removal activity of nitrogen oxide at 200 ° C or less by improving the oxidation / reduction ability at low temperature and improving the dispersion degree of manganese. In addition, the study on the improvement of durability against hydrogen fluoride through addition of co-catalyst is also lacking. Considering this situation, it is necessary to study and develop a method to improve the durability of the catalyst and hydrogen fluoride complexity.

[Patent Literature]

- Patent Application Publication No. 10-2010-0001315 (2010.01.06.)

[Non-Patent Document]

- Non-Patent Document 1: Chemical Engineering Journal, 195-196, pp.323-331, 2012.

- Non-patent document 2: Applied Catalysis B Environmental, 129, pp.30-38, 2013.

DISCLOSURE Technical Problem The present invention has been made to solve the above problems, and it is an object of the present invention to provide a manganese-based catalyst exhibiting excellent nitrogen oxide (NOx) removal activity at a low temperature region of 200 ° C or lower and having durability against hydrogen fluoride, Thereby removing nitrogen oxides.

In order to solve the above problems, the present invention provides a method for preparing a catalyst for removing nitrogen oxides by supporting an active material containing manganese and ceria on a titania carrier, which comprises the step of adding tungsten to control the oxidation of manganese and ceria Ceria-tungsten-titania catalyst for removal of nitrogen oxides.

Also, the present invention provides a method for preparing a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides, wherein the tungsten is added in an amount of 3 to 7 parts by weight based on 100 parts by weight of the titania support.

The manganese-ceria-tungsten-titania catalyst is prepared by carrying the tungsten and the ceria on the titania carrier, drying and calcining the ceria-tungsten-titania catalyst to prepare the ceria-tungsten-titania catalyst, Cerium-tungsten-titania catalyst for removing nitrogen oxides, characterized in that the catalyst is prepared by drying, calcining, and drying.

Also, the present invention provides a method for preparing a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides, wherein the manganese-ceria-tungsten-titania catalyst is prepared by simultaneously supporting, drying and firing tungsten, ceria and manganese .

Also, the present invention provides a method for preparing a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides, wherein the calcination is carried out at a temperature of 300 to 500 ° C for 0.5 to 5 hours in a furnace in a gaseous atmosphere containing nitrogen and oxygen .

Further, the tungsten is in the ammonium meta tungstate _{((NH 4) 6 H 2} W 12 O 40 · xH 2 O) , or ammonium paratungstate _{((NH 4) 10 H 2} (W 2 O 7) 6) as the precursor Cerium-tungsten-titania catalyst for removing nitrogen oxides.

In addition, the ceria a ceria nitrate _{(Ce (NO 3) 3 ·} xH 2 O), ceria acetate _{(Ce (CH 3 CO 2)} 3 · xH 2 O), ceria oxalate light _{(Ce 2 (C 2 O 4} ) 3 provides a process for producing titania catalyst - · xH ₂ O) and ceria oxide (CeO ₂₎ manganese for nitrogen oxide removal, characterized in that to be added to the precursor to at least one member selected from the group consisting of-ceria-tungsten.

And the manganese is added as a precursor of manganese nitrate (Mn (NO ₃ ) ₂ .xH ₂ O) or manganese acetate tetrahydrate ((C ₂ H ₃ O ₂ ) ₂ Mn · 4H ₂ O) Ceria-tungsten-titania catalyst for removing nitrogen oxides.

In order to solve the above-mentioned problems, the present invention provides a catalyst for removal of nitrogen oxides in which an active material containing manganese and ceria is supported on a titania carrier, and a catalyst for removing nitrogen oxides to which tungsten is added for controlling oxidation of manganese and ceria Manganese-ceria-tungsten-titania catalyst.

Also, the present invention provides a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides, wherein the tungsten is added in an amount of 3 to 7 parts by weight based on 100 parts by weight of the titania support.

Also, the present invention provides a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides, wherein the catalyst has a tetravalent manganese atomic ratio (Mn ^{4 +} / Mn) of not less than 0.36 with respect to all manganese.

Also, the catalyst of the present invention provides a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides, which is characterized in that the trivalent ceria atom ratio (Ce ³⁺ / Ce) of oxidation to total ceria is 0.25 or more.

According to another aspect of the present invention, there is provided a method for removing nitrogen oxides by passing an exhaust gas containing ammonia, nitrogen oxides, air, and moisture through a catalyst according to any one of claims 9 to 12.

And the nitrogen oxide removal is carried out at a temperature of 120 to 200 ° C.

And the exhaust gas further comprises hydrogen fluoride (HF).

According to the present invention, as tungsten is supported on the catalyst for removing nitrogen oxides, the oxidation of manganese to the entire manganese is controlled by controlling the manganese oxidation of the catalyst to increase the ratio (Mn ^{4 +} / Mn) of the number of atoms per unit volume , And the oxidation of ceria to total ceria through the control of the ceria oxidation of the catalyst increases the ratio of the number of atoms per unit volume of the trivalent ceria (Ce ^{3 +} / Ce), so that the excellent nitrogen oxide removal efficiency And a process for producing the same.

Also, it is possible to provide a catalyst for removing nitrogen oxide, which is excellent in durability against hydrogen fluoride generated during the treatment of a gas generated in a semiconductor manufacturing process, and a method for producing the same.

1 is a graph showing the relationship between the manganese oxidation state of the catalyst prepared according to Production Example 1, Production Example 2 and Production Example 4 of the present invention, and the oxidation of manganese to total manganese in terms of the number of atoms per unit volume (Mn ^{4 +} / Mn) A graph showing the ratio,
2 is a graph showing the relationship between the oxidation of total manganese of the catalyst prepared according to Production Example 1, Production Example 2 and Production Example 4 of the present invention to the ratio of the number of atoms per unit volume (Mn ^{4 +} / Mn) A graph showing the removal efficiency,
3 is a graph showing NH ₃ -TPD results of the catalysts prepared according to Production Example 1, Production Example 2 and Production Example 4 of the present invention,
4 shows the ratio of the number of atoms per unit volume of the trivalent ceria (Ce ^{3 +} / Ce) to the ceria oxidation state of the catalyst prepared according to Production Examples 2 to 6 of the present invention and oxidation of the total ceria graph,
5 is a graph showing the relationship between the oxidation efficiency of the catalyst prepared according to Production Examples 2 to 6 of the present invention and the total ceria of the catalyst according to the ratio of the number of atoms per unit volume of trivalent ceria (Ce ^{3 +} / Ce) A graph.

Hereinafter, preferred embodiments of the present invention will be described in detail. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Throughout the specification, when an element is referred to as "including " an element, it means that it can include other elements, not excluding other elements, unless specifically stated otherwise.

The present inventors have found that, in a method for preparing a catalyst for removing nitrogen oxides by supporting an active material containing manganese and ceria on a titania carrier, the manganese oxidation of the catalyst is controlled and the ceria oxidation is controlled at 200 ° C And can achieve excellent nitrogen oxide removal efficiency even in the low temperature region below. Hereinafter, the production process of the catalyst for removing nitrogen oxides according to the present invention will be described in detail.

The manganese-ceria-tungsten-titania catalyst for removal of nitrogen oxides according to the present invention can control the oxidation of manganese and ceria by using tungsten, exhibits excellent nitrogen oxide removal efficiency at a low temperature region of 200 ° C or less, As a catalyst, manganese, ceria and tungsten are supported on titania and dried and fired. That is, the manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides according to the present invention can be produced by artificially changing the physical properties of the catalyst through the addition of a cocatalyst to maximize the activity of the catalyst for selectively converting nitrogen oxides and the durability against hydrogen fluoride will be.

X-ray photoelectron spectroscopy (XPS) analysis is used as a means for analyzing the oxidation state of manganese and ceria supported in the present invention. According to the XPS analysis, the characteristic peaks of the respective elements present on the surface of the catalyst are separated on the basis of the binding energy of the oxides containing the elements, and the kind and the distribution of the oxides present on the surface of the catalyst The ratio can be analyzed, and each peak can be separated by Gaussian-Lorentzian (Gaussian-Lorentzian) method. The number of Mn ^{x +} and Ce ^{y +} atoms is calculated by taking the area (number of characteristic photoelectrons obtained per unit time) obtained from the XPS analysis into consideration of the atomic sensitivity factor and determining the number of the element per unit volume (cm 3) The number of atoms can be obtained. The number of atoms per atomic unit (atoms / cm 3) of elemental species represented by Mn ^{x +} and Ce ^{y +} calculated by this method can be measured. Therefore, according to the XPS analysis, it was confirmed that the change of the oxidation of manganese and ceria according to the addition of the cocatalyst in the present invention directly affects the activity of the catalyst for converting nitrogen oxide into nitrogen at low temperature and the durability against hydrogen fluoride Can be confirmed.

In the present invention, the carrying process can be carried out by impregnation as a method for carrying manganese, ceria or tungsten, which is an active metal, on titania as a support. Specifically, the active metal precursor is quantitatively determined based on the weight of the titania carrier, dissolved in an aqueous solution, and the prepared titania carrier and the aqueous solution in which the active metal precursor is dissolved are sufficiently mixed to prepare a slurry slurry.

(NH ₄ ) ₆ H ₂ W ₁₂ O ₄₀ .xH ₂ O) or ammonium paratungstate ((NH ₄ ) ₁₀ H ₂ (W ₂ O ₇ )) as a precursor for the tungsten support, ₆ ) is preferably used. At this time, the oxidation of the total manganese to the tetragonal manganese atom ratio (Mn ^{4 +} / Mn) and the oxidation to the total ceria increase the tungsten content to increase the catalytic activity by increasing the trivalent ceria atom ratio (Ce ^{3 +} / Ce) (Based on the tungsten element) is preferably 1 to 10 parts by weight, more preferably 3 to 7 parts by weight, and most preferably 4 to 6 parts by weight based on 100 parts by weight of the titania carrier.

The precursor that is used for the ceria-supported is ceria nitrate _{(Ce (NO 3) 3 ·} xH 2 O), ceria acetate _{(Ce (CH 3 CO 2)} 3 · xH 2 O), ceria oxalate light (Ce ₂ ( (C ₂ O ₄ ) ₃ .xH ₂ O) and ceria oxide (CeO ₂ ). However, the selective reaction of the catalyst prepared in the above-mentioned preferable range of tungsten content to nitrogen oxides It is not particularly limited as long as it does not deteriorate.

The supported ceria content (based on the ceria element) is preferably 1 to 20 parts by weight, more preferably 2 to 10 parts by weight, and most preferably 3 to 5 parts by weight based on 100 parts by weight of the titania support. As the content of the ceria decreases, the selectivity of the catalyst to the nitrogen oxide of the final catalyst tends to increase. However, when the ceria content exceeds a certain range, the catalyst tends to decrease. That is, when the ceria content is less than 1 part by weight, the conversion of nitrogen oxides may not be satisfactory. When the ceria content is more than 20 parts by weight, the decrease of the nitrogen oxide conversion ratio may become significant.

Manganese nitrate (Mn (NO ₃ ) ₂ .xH ₂ O) or manganese acetate tetrahydrate ((C ₂ H ₃ O ₂ ) ₂ Mn · 4H ₂ O) may be used as the precursor used for supporting the manganese , So long as it does not deteriorate the selective reaction of the finally produced catalyst to the nitrogen oxide in the above-described preferable tungsten content range.

The supported manganese content (based on manganese element) is preferably 1 to 50 parts by weight, more preferably 5 to 40 parts by weight, and most preferably 10 to 30 parts by weight based on 100 parts by weight of the titania support.

After that, the water content of the prepared slurry is removed by using a rotary vacuum evaporator, and residual moisture contained in the micropores in the slurry can be sufficiently dried and removed in a dryer. For example, it can be dried by using a drier at a temperature of 90 to 115 ° C, preferably 100 to 105 ° C for at least 24 hours.

Thereafter, the dried sample is sintered to control the size and the degree of dispersion of the active metal through heat treatment. The firing process may be performed in a gas atmosphere containing nitrogen and oxygen in consideration of conversion efficiency and energy efficiency for nitrogen oxides, for example, at a temperature of 200 to 500 ° C for 0.5 to 5 hours. Since the firing temperature may lower the selective reaction efficiency with respect to nitrogen oxides at a relatively high temperature, the firing temperature is more preferably 300 to 400 ° C. Also, the firing time may preferably be 2 to 4 hours, considering the selective oxidation ability of ammonia of the catalyst. The firing process may be performed in various types of furnaces, such as a tube type, a convection type, and a grate type, and is not particularly limited.

The manganese-ceria-tungsten-titania catalyst produced according to the present invention can selectively remove nitrogen oxides in the exhaust gas with high efficiency.

Meanwhile, the catalyst for removing nitrogen oxides according to the present invention may be extruded in the form of particles or monoliths together with a small amount of binder as well as powders, or may be prepared in various forms such as slates, plates, and pellets.

In addition, when the catalyst for removing nitrogen oxides according to the present invention is actually applied, it is possible to coat a structure such as a metal plate, a metal fiber, a ceramic filter, a honeycomb, a glass tube, an air purifier, an interior decoration, It can also be used in downstream industrial processes where flue gas containing hydrogen is generated.

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

Manufacturing example  One

To prepare a manganese-titania catalyst for removal of nitrogen oxide, manganese nitrate (Mn (NO ₃ ) ₂ .xH ₂ O, Aldrich Chemical Co.) as a manganese precursor was quantified to be 20 parts by weight based on 100 parts by weight of the titania carrier, Lt; 0 > C or more to prepare a manganese precursor aqueous solution. Subsequently, a manganese precursor solution and titania were mixed to prepare a slurry. After removing moisture using a vacuum rotary evaporator, thoroughly dry the slurry in a dryer at 103 ° C for one day to completely remove the moisture contained in the micropores. Finally, a manganese-titania catalyst was prepared by firing in a tube furnace at a temperature of 400 DEG C for 4 hours in an air atmosphere.

Manufacturing example  2

To prepare a manganese-ceria-titania catalyst for removal of nitrogen oxide, cerium nitrate (Ce (NO ₃ ) ₃ .6H ₂ O) was quantitatively determined to be 4 parts by weight based on 100 parts by weight of titania and then dissolved in distilled water To prepare a ceria aqueous solution. The prepared ceria aqueous solution and titania were mixed to prepare a slurry form. Then, the water was removed using a vacuum rotary evaporator, and sufficiently dried for more than one day in a dryer at 103 ° C to completely remove the moisture contained in the micropores. Then, the ceria-titania is produced in a tube-type furnace at a temperature of 400 DEG C for 4 hours under an air atmosphere. Subsequently, a manganese precursor aqueous solution (quantitatively determined to be 20 parts by weight based on 100 parts by weight of the titania carrier) and ceria-titania were mixed to prepare a slurry, and then water was removed using a vacuum rotary evaporator. Dry thoroughly for more than one day in a 103 ° C dryer to remove completely. Finally, a manganese-ceria-titania catalyst was prepared by firing in a tube furnace at a temperature of 400 DEG C for 4 hours in an air atmosphere.

Manufacturing example  3

To prepare a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxide, ammonium tungsten ((NH ₄ ) ₆ H ₂ W ₁₂ O ₄₀ .xH ₂ O) was quantified to be 3 parts by weight based on 100 parts by weight of titania, Or more in distilled water heated to prepare a tungsten aqueous solution. Subsequently, cerium nitrate (Ce (NO ₃ ) ₃ .6H ₂ O) was quantitatively determined to be 4 parts by weight based on 100 parts by weight of titania, and dissolved in distilled water heated to 60 ° C or more to prepare a ceria aqueous solution. The prepared tungsten aqueous solution, ceria aqueous solution and titania were mixed to prepare a slurry, and then the water was removed by using a vacuum rotary evaporator. After thorough drying for more than one day in a dryer at 103 ° C to completely remove moisture contained in the micropores . Then, in a tube-type furnace, firing is performed at 400 ° C for 4 hours in an air atmosphere to produce ceria-tungsten-titania. Subsequently, a manganese precursor aqueous solution (quantitatively determined to be 20 parts by weight based on 100 parts by weight of the titania support) and ceria-tungsten-titania were mixed to prepare a slurry, followed by removing water using a vacuum rotary evaporator, Dry thoroughly for more than one day in a 103 ° C dryer to remove moisture completely. Finally, a manganese-ceria-tungsten-titania catalyst was prepared by firing in a tube furnace at a temperature of 400 ° C. for 4 hours under an air atmosphere.

Manufacturing example  4

A manganese-ceria-tungsten-titania catalyst was prepared in the same manner as in Preparation Example 3, except that tungsten was added in an amount of 5 parts by weight based on 100 parts by weight of titania in the tungsten addition process of Production Example 3 .

Manufacturing example  5

A manganese-ceria-tungsten-titania catalyst was prepared in the same manner as in Preparation Example 3, except that tungsten was used in an amount of 7 parts by weight based on 100 parts by weight of titania in the tungsten addition process of Production Example 3 .

Manufacturing example  6

A manganese-ceria-tungsten-titania catalyst was prepared in the same manner as in Production Example 3, except that tungsten was added in an amount of 10 parts by weight based on 100 parts by weight of titania in the tungsten addition process of Production Example 3 .

Manufacturing example  7

In Preparation Example 4, a manganese aqueous solution, a ceria aqueous solution and an aqueous tungsten solution were mixed with titania to prepare a slurry. Then, water was removed using a vacuum rotary evaporator, and the water contained in the micropores was completely removed. Dry well over a day. Finally, a manganese-ceria-tungsten-titania catalyst was prepared by firing in a tube furnace at a temperature of 400 ° C. for 4 hours in an air atmosphere.

Comparative Manufacturing Example  One

A manganese-ceria-titania catalyst was prepared in the same manner as in Production Example 2, except that ceria oxide (CeO ₂ ) was used as a ceria precursor in Production Example 2.

Comparative Manufacturing Example  2

A manganese-ceria-molybdenum-titania catalyst was prepared in the same manner as in Production Example 3, except that molybdenum was supported instead of tungsten in Production Example 3. As a precursor of molybdenum, ammonium molybdate ((NH ₄ ) ₆ MO ₇ O ₂₄ .4H ₂ O) was used, and 5 parts by weight (based on molybdenum element) of 100 parts by weight of titania was supported.

Comparative Manufacturing Example  3

A manganese-ceria-tin-titania catalyst was prepared in the same manner as in Production Example 3, except that tin was supported instead of tungsten in Production Example 3. As a precursor of tin, tin acetate (Sn (CH ₃ CO ₂ ) ₄ ) was used, and 2 parts by weight (based on tin element) was supported on the basis of 100 parts by weight of titania.

Comparative Manufacturing Example  4

A manganese-ceria-nickel-titania catalyst was prepared in the same manner as in Production Example 3, except that tungsten was replaced with nickel in Production Example 3. Nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) was used as a precursor of nickel, and 8.5 parts by weight (based on nickel element) was carried on the basis of 100 parts by weight of titania.

The catalyst compositions according to the above Production Examples are shown in Table 1 below.

Example  One

NOx to evaluate the SCR reaction characteristic to determine the NOx removal efficiency of the catalyst in the space velocity 30,000hr ^-1 condition with respect to the catalyst prepared according to Production Example 1, Production Example 2 and Comparative Preparation Example 1 according to the ceria-supported ( NOx) was measured. The results are shown in Table 2 below. The experimental conditions and measurement method are as follows, which is the same in Examples 2 to 3 to be described later.

[Experimental Conditions]

The gas injected into the catalytic reactor had a gaseous nitrogen oxide concentration of 200 ppm, an oxygen concentration of 8%, a relative humidity of 8%, an inlet flow rate of 600 cc / min, a space velocity of 30,000 hr ^-1 under an air (N ₂ ) atmosphere, Experiments were carried out at 200 ° C. For reference, the space velocity is an indicator of the amount of the target gas that can be treated by the catalyst, and is represented by the volume ratio of the catalyst to the total gas flow rate (volume).

[How to measure]

The gas phase nitrogen oxide conversion was calculated according to the following equation. Also, the nitrogen conversion was calculated by measuring the concentration of nitrogen oxides generated by the unreacted gaseous nitrogen oxides being injected, using a non-dispersive infrared gas analyzer (ZKJ-2, Fuji Electric Co.). In addition, the ammonia concentration in the gaseous phase was measured using a detector tube to measure the NH ₃ slip caused by the unreacted gaseous ammonia injected as a reducing agent.

Referring to Table 2, the nitrogen oxide removal ratios of Production Example 1, Production Example 2 and Comparative Production Example 1 were examined, and the overall efficiency improvement effect was confirmed by adding ceria. In particular, when the precursor of ceria nitrate (Ce (NO ₃ ) ₃ .6H ₂ O) of Production Example ₂ was used, it was confirmed that the conversion of nitrogen oxide was superior to that of ceria oxide (CeO ₂ ) of Comparative Preparation Example 1 as a precursor .

Example  2

Based on the results in Example 1, experiments were conducted on the catalysts prepared in Preparation Examples 2 to 6 to further confirm the effect of the addition of tungsten on the conversion of nitrogen oxides. The results are shown in Table 3 below. . Experimental conditions and methods are the same as in Example 1.

As shown in Table 3, the nitrogen oxide removal efficiency of Production Example 4, in which tungsten was added in an amount of 5 parts by weight based on the weight of titania, It can be seen that it is excellent.

Example  3

In order to simplify the manufacturing process of the manganese-ceria-tungsten-titania catalyst, the nitrogen oxide removal test of Production Example 7 was carried out in which the active material and the co-catalyst were supported at one time in the catalyst preparation stage. In order to confirm the efficiency, a comparative experiment with the catalyst prepared in Production Example 4 was carried out. The results are shown in Table 4 below. Experimental conditions and methods are the same as in Example 1.

Referring to Table 4, it can be seen that there is no significant difference in conversion efficiency activity between nitrogen oxides in Production Example 4 and Production Example 7. It is significant that the catalyst can be manufactured by a simple production process by reducing the heat treatment step by one in the production process of the catalyst according to Production Example 7. [

Example  4

The results of XPS analysis of Mn 2p for the catalyst prepared according to Preparation Example 1 are shown in FIG. 1 by Gaussian-Lorentzia method. The results are shown in Table 1. In the same manner, Mn of the catalyst prepared according to Production Example 2 and Production Example 4 The results of XPS analysis of 2p show the types and distribution ratios of manganese oxides present on the catalyst surface. Based on the results of this analysis, the nitrogen oxide removal efficiency according to the ratio of the number of atoms per unit volume (Mn ^{4 +} / Mn) of the quadrivalent manganese to the total manganese is shown in FIG.

Referring to FIGS. 1 and 2, the ratio of the number of atoms per unit volume (Mn ^{4 +} / Mn) of tetravalent manganese to total manganese was increased in the order of Production Example 4, Production Example 2 and Production Example 1, As shown in FIG. 2, the nitrogen oxide conversion rate was also increased as the ratio of the number of atoms per unit volume (Mn ^{4 +} / Mn) of tetravalent manganese to total manganese increased.

Next, in order to confirm the influence of the degree of dispersion of manganese on the ammonia adsorption, ammonia TPD experiment was carried out, and the results are shown in FIG.

As shown in Fig. 3, the increase of the acid sites can be confirmed in the order of Production Example 4, Production Example 2, and Production Example 1. Therefore, when ceria and ceria-tungsten are added as cocatalysts to the manganese-titania catalyst, the acid sites of the catalyst are increased to increase the adsorption sites, thereby improving the ammonia adsorption characteristics.

Example  5

The XPS analysis was carried out in the same manner as in Example 4 to measure the oxidation yield to ceria formed on the surface of the catalyst. The results of the XPS analysis of Ce 3d for the catalyst prepared according to Preparation Example 2 were shown in FIG. 4 by the Gaussian-Lorentzia method and the results of XPS analysis of Ce 3d for Production Examples 3 to 6 And the kind and distribution ratio of ceria oxide present on the catalyst surface were analyzed.

As shown in FIG. 4, the ratio of the number of atoms per unit volume (Ce ^{3 +} / Ce) of the trivalent ceria to the highest total ceria in the catalyst prepared in Production Example 4, and the tungsten content exceeded 5 parts by weight And it tends to decrease when it is carried.

Based on the results of the analysis, the nitrogen oxide removal efficiency according to the ratio of the number of atoms per unit volume (Ce ^{3 +} / Ce) of trivalent ceria to total ceria is shown in FIG. It can be seen that as the ratio of the number of atoms per unit volume (Ce ^{3 +} / Ce) of trivalent ceria to total ceria increases, the conversion of nitrogen oxides increases.

Example  6

In order to confirm the effect of tungsten on hydrogen fluoride (HF) in the catalyst for removing nitrogen oxide prepared according to the present invention, the catalyst prepared according to Production Example 2, Production Example 4 and Production Example 6 was subjected to a nitrogen oxide removal reaction The durability test of the catalyst by injecting hydrogen fluoride was performed according to the following experimental conditions, and the results are shown in Table 5 below.

[Experimental Conditions]

Injected gas is air (N ₂₎ under a gaseous nitrogen oxide concentration atmosphere is 54ppm, the oxygen of 8% and a relative humidity of 8% HF 5ppm, a space velocity of 7,000hr ^-1, the test temperature of the catalytic reactor is carried out an experiment in 180 ℃ Respectively. HF durability The catalyst used in the experiment was a pellet type catalyst with a diameter of 3 mm.

Referring to Table 5, it can be seen that the catalyst prepared in Preparation Example 4 having the highest initial nitrogen oxide conversion rate has excellent durability against HF.

The preferred embodiments of the present invention have been described in detail above. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning, range, and equivalence of the claims are included in the scope of the present invention Should be interpreted.

Claims (15)

A method for producing a catalyst for removing nitrogen oxides by supporting an active material containing manganese and ceria on a titania carrier,
Wherein the oxidation of manganese and ceria is carried out by adding tungsten in an amount of 3 to 7 parts by weight based on 100 parts by weight of the titania support, process for producing titania catalyst - Mn ⁴⁺ / Mn) of manganese for nitrogen oxide removal, characterized in that the adjustment outside the 0.36-ceria-tungsten. delete The method according to claim 1,
The manganese-ceria-tungsten-titania catalyst is prepared by carrying the tungsten and the ceria on the titania carrier, drying and firing the ceria-tungsten-titania catalyst, adding the manganese with the ceria-tungsten- Cerium-tungsten-titania catalyst for removing nitrogen oxides. The method according to claim 1,
Wherein the manganese-ceria-tungsten-titania catalyst is prepared by simultaneously supporting the tungsten, ceria, and manganese, drying and firing the manganese-ceria-tungsten-titania catalyst. The method according to claim 3 or 4,
Wherein the calcination is performed at a temperature of 300 to 500 ° C for 0.5 to 5 hours in a furnace in a gas atmosphere containing nitrogen and oxygen. The method according to claim 1,
The tungsten is added as a precursor of ammonium metatungstate ((NH ₄ ) ₆ H ₂ W ₁₂ O ₄₀ ) or ammonium paratungstate ((NH ₄ ) ₁₀ H ₂ (W ₂ O ₇ ) ₆ ) Wherein the catalyst is prepared by a method comprising the steps of: (a) preparing a manganese-ceria-tungsten-titania catalyst for removal of nitrogen oxides; The method according to claim 1,
The ceria a ceria nitrate _{(Ce (NO 3) 3 ·} 6H 2 O), ceria acetate _{(Ce (CH 3 CO 2)} 3), ceria oxalate light _{(Ce 2 (C 2 O 4} ) 3) and ceria oxide ( CeO ₂ ) is added as a precursor. The method for producing a manganese-ceria-tungsten-titania catalyst for removing nitrogen oxides according to claim 1, The method according to claim 1,
Wherein the manganese is added as a precursor to manganese nitrate (Mn (NO ₃ ) ₂ ) or manganese acetate tetrahydrate ((C ₂ H ₃ O ₂ ) ₂ Mn · 4H ₂ O) -Ceria-tungsten-titania catalyst. A catalyst for removing nitrogen oxides in which an active material including manganese and ceria is supported on a titania carrier, wherein tungsten is further added in an amount of 3 to 7 parts by weight based on 100 parts by weight of the titania carrier for controlling oxidation of manganese and ceria Wherein the catalyst has a tetravalent manganese atomic ratio (Mn ⁴⁺ / Mn) of not less than 0.36 with respect to the total manganese. delete delete 10. The method of claim 9,
Wherein the catalyst has a trivalent ceria atomic ratio (Ce ³⁺ / Ce) of not less than 0.25 for oxidation to total ceria. A method for removing nitrogen oxides by passing an exhaust gas containing ammonia, nitrogen oxide, air, and moisture through a catalyst according to any one of claims 9 to 12. 14. The method of claim 13,
Wherein the nitrogen oxide removal is performed at a temperature of 120 to 200 ° C. 14. The method of claim 13,
Wherein the exhaust gas further comprises hydrogen fluoride (HF).

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