KR20230039631A - Non-platinum metal oxide catalyst for selective oxidation of ammonia and process for selective oxidation of ammonia using the same - Google Patents

Abstract

The present invention relates to a non-platinum metal oxide catalyst for conversion of ammonia to nitrogen and a method for conversion of ammonia to nitrogen using the same, and more specifically, to a non-platinum metal oxide catalyst for conversion of ammonia to nitrogen, which, as a non-platinum metal oxide catalyst containing cerium (Ce), zirconium (Zr), copper (Cu) and silver (Ag), shows a molar ratio of a first metal composed of cerium and zirconium and a second metal composed of copper and silver of 1 : 1 to 3 : 1, and a molar ratio of copper / silver of 7 or less, and a method for conversion of ammonia to nitrogen using the same.

Description

Non-platinum metal oxide catalyst for nitrogen conversion of ammonia and method for converting ammonia to nitrogen using the same

The present invention relates to a non-platinum metal oxide catalyst for converting ammonia to nitrogen and a method for converting ammonia to nitrogen using the same.

More specifically, as a non-platinum metal oxide catalyst including cerium (Ce), zirconium (Zr), copper (Cu), and silver (Ag), a first metal composed of cerium and zirconium and a second metal composed of copper and silver It relates to a non-platinum metal oxide catalyst for nitrogen conversion of ammonia, characterized in that the molar ratio of is 1:1 to 3:1 and the molar ratio of copper/silver is 7 or less, and a method for converting ammonia to nitrogen using the same.

Recently, with continuous industrial development and economic growth, energy consumption is rapidly increasing. As a result, the problem of environmental pollution is emerging as a serious issue. Among them, air pollution has not only diverse sources, but is not a local problem limited to the region where the source is located, but also affects neighboring countries by diffusion due to the nature of air pollution. Because of this, it is subject to international regulation. Among various air pollutants, ammonia is an odor-causing substance that causes discomfort even at low concentrations. When directly exposed to the human body, ammonia causes irritation to the eyes, nose, and skin. In addition, ultrafine dust (PM2.5), which has recently become a problem, is generated by reacting with sulfurous acid gas or nitrogen oxide when ammonia discharged from various industrial facilities and automobiles behaves in the atmosphere. When the generated ultrafine dust is absorbed into the human body, conjunctivitis, rhinitis, asthma, and alveolar damage can be caused. In addition, ammonia in the flue gas is corrosive when present together with moisture, which has a harmful effect on industrial facilities and animals and plants. In particular, when coexisting with sulfur dioxide (SO ₂ ) components in exhaust gas, salts such as ammonium sulfate and ammonium bisulfate are generated, which causes blockage and corrosion of the flow path in the process. However, the development of treatment technology for nitrogen compounds such as ammonia is remarkably low compared to its importance. Currently, in the case of ammonia, it is discharged from various chemical facilities using urea as a raw material, and a large amount is also included in wastewater. In addition, it is included in exhaust gas from denitrification facilities installed in automobiles and thermal power plants to remove nitrogen oxides and is discharged into the atmosphere. Accordingly, regulations on the concentration of ammonia contained in flue gas and wastewater are being strengthened.

Conventionally, as ammonia treatment technologies to satisfy the emission regulation value of ammonia, a biological treatment method, an adsorption method, an incineration method, a catalytic oxidation method using a catalyst, and the like are used. However, in the case of biological treatment, there is a disadvantage that periodic microorganisms must be managed and the treatment capacity is affected depending on the season because it is sensitive to temperature. . On the other hand, in the case of selective oxidation of ammonia using a catalyst, it is in the spotlight as the most efficient ammonia treatment technology from an economic or environmental point of view.

On the other hand, in the selective catalytic oxidation reaction, ideally, a reaction in which ammonia reacts with oxygen and is directly oxidized to nitrogen harmless to the human body should be the main reaction, but in most cases, ammonia is oxidized to other nitrogen oxides such as It is very important to suppress this reaction because it has the disadvantage of generating secondary pollutants. Therefore, various studies are being actively conducted to solve these problems.

Specifically, an example of a selective oxidation catalyst for converting gaseous ammonia into nitrogen is disclosed in Korean Patent Publication No. 10-2007-0112201. According to the above published patent, ammonia can be treated at a temperature between 300 ° C and 500 ° C, but at a low temperature of 300 ° C. Ammonia conversion and nitrogen selectivity are shown. In addition, another example of a catalyst for removing ammonia is disclosed in Korean Patent Laid-open Publication No. 10-2012-0128029, and according to the published patent, an ammonia conversion rate of 90% or more and a conversion rate to nitrogen of 75% or more at a temperature of 340 to 450 ° C. However, it requires a high reaction temperature of 340 ℃ or more.

Accordingly, the recent research trend on oxidation catalysts for removing gaseous ammonia is to use noble metals such as platinum, palladium, and rhodium as active metals at low reaction temperatures of 200 to 300 ° C. Research is being conducted, but in the case of ammonia oxidation catalysts using active metals as noble metals, the problem that most of the removed ammonia is converted to nitrogen oxides (NO, NO ₂ , N ₂ O) still exists. To solve this problem, Korean Patent Publication No. 10-2011-0086720 and Non-Patent Document 1 (Applied Surface Science, 402, pp. 323-329, 2017) disclose that a catalyst using an active metal as a noble metal is mixed with a non-noble metal-based material. Attempts have been made to develop a technique for increasing ammonia conversion and selectivity to nitrogen through mixing, but satisfactory effects have not been shown in relation to ammonia conversion and selectivity to nitrogen at 300 ° C or less.

Meanwhile, the inventors of the present invention have disclosed a non-platinum-based metal oxide catalyst for low-temperature oxidation of volatile organic compounds having performance equivalent to that of a platinum group metal catalyst in Korean Patent Registration No. 10-1834271 as a prior registered patent, and the catalyst is cerium It is a composite metal oxide catalyst containing (Ce), zirconium (Zr), copper (Cu) and silver (Ag). It is economical, thermally stable, and has oxygen storage and oxygen transfer capabilities compared to platinum group metal catalysts known to have excellent performance. It has been shown that the efficiency of removing volatile organic compounds in the low-temperature region has an excellent effect.

In the present invention, it was found that the non-platinum-based metal oxide catalyst is very effective for low-temperature oxidation of volatile organic compounds as well as conversion of ammonia to nitrogen, and the present invention was completed as a use invention for using the catalyst for a specific purpose of conversion of ammonia to nitrogen.

Republic of Korea Patent Publication No. 10-2007-0112201. Republic of Korea Patent Publication No. 10-2012-0128029. Republic of Korea Patent Publication No. 10-2011-0086720. Republic of Korea Patent Registration No. 10-1834271.

Applied Surface Science, 402, pp. 323-329, 2017.

The present invention was developed to solve the above problems, and has excellent ammonia oxidation and It is an object to provide a non-platinum-based metal oxide catalyst having a conversion rate to nitrogen.

In addition, an object of the present invention is to provide a method for converting ammonia to nitrogen using a non-platinum metal oxide catalyst.

In the present invention, in order to solve the above problems, a non-platinum metal oxide catalyst containing cerium (Ce), zirconium (Zr), copper (Cu) and silver (Ag), a first metal consisting of cerium and zirconium and copper and silver It provides a non-platinum metal oxide catalyst for nitrogen conversion of ammonia, characterized in that the molar ratio of the second metal is 1:1 to 3:1 and the molar ratio of copper/silver is 7 or less.

In addition, the present invention provides a method for converting ammonia to nitrogen, comprising the step of contacting the prepared non-platinum metal oxide catalyst for nitrogen conversion of ammonia with ammonia.

The non-platinum metal oxide catalyst containing cerium (Ce), zirconium (Zr), copper (Cu), and silver (Ag) according to the present invention is a catalyst for selective oxidation of ammonia with excellent ammonia removal efficiency and selectivity to nitrogen.

Unlike the conventional method of supporting an active metal component on a simple titania carrier, the present invention has a molar ratio of the first metal composed of cerium and zirconium to the second metal composed of copper and silver of 1:1 to 3:1, and copper/zirconium. By adjusting the molar ratio of silver to 7 or less, the catalytic function of the active metal is further enhanced, so that the selectivity of nitrogen is greatly improved in the range of 200 to 300 ° C.

1 shows test conditions for nitrogen conversion of ammonia using a catalyst according to an embodiment of the present invention and a conversion rate accordingly.
2 shows test conditions and results of ammonia conversion to nitrogen using a Pt ₇ Pd ₁ /Al ₂ O ₃ catalyst according to an embodiment of the present invention.
Figure 3 shows test conditions and results for nitrogen conversion of ammonia using a CZCuAg catalyst, which is an embodiment of the present invention.
Figure 4 shows the results of comparing the nitrogen conversion rate of ammonia according to the temperature with respect to the type of catalyst, which is an embodiment of the present invention.
Figure 5 shows the results of comparing the nitrogen conversion rate of ammonia according to the temperature with respect to the type of catalyst under moisture conditions, which is an embodiment of the present invention.
Figure 6 shows the results of comparing the selectivity of nitrogen according to the temperature with respect to the type of catalyst under moisture conditions, which is an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The term 'non-platinum-based metal oxide catalyst for nitrogen conversion of ammonia' used throughout this specification refers to the limited use of a non-platinum-based metal oxide catalyst for a specific purpose of nitrogen conversion of ammonia.

That is, ammonia, which is a new use of a non-platinum-based metal oxide catalyst for low-temperature oxidation of volatile organic compounds having performance comparable to that of the platinum group metal catalyst disclosed in Korean Patent Registration No. 10-1834271, which is a prior registered patent by the inventors of the present invention It relates to a use invention found to be very effective in nitrogen conversion or oxidation of ammonia.

On the other hand, 'Volatile Organic Compounds (VOCs)' are designated as compounds such as volatile alcohols, ketones, esters, ethers, aldehydes, and aromatics in accordance with Article 2, Article 10 of the Clean Air Conservation Act. It does not contain ammonia or nitrogen oxides, etc. Catalysts for reducing VOCs convert carbon-based VOCs into carbon dioxide and water, so the reactivity of carbon-carbon bonds is important. On the other hand, since there is no carbon-carbon bond in the nitrogen conversion reaction of ammonia and the reactivity of the nitrogen-hydrogen bond is important, there is a technical difference. In addition, the selectivity of converting ammonia into nitrogen rather than nitrogen oxide is also very important. Therefore, in general, when a catalyst for reducing VOC is used as an ammonia nitrogen conversion catalyst, good performance is not shown.

In the present invention, in order to solve the above problems, a non-platinum metal oxide catalyst containing cerium (Ce), zirconium (Zr), copper (Cu) and silver (Ag), a first metal consisting of cerium and zirconium and copper and silver It provides a non-platinum metal oxide catalyst for nitrogen conversion of ammonia, characterized in that the molar ratio of the second metal is 1:1 to 3:1 and the molar ratio of copper/silver is 7 or less.

According to one embodiment of the present invention, the molar ratio of the first metal consisting of cerium and zirconium and the second metal consisting of copper and silver may range from 0.1 to 10:1, preferably from 0.5 to 5:1. , more preferably 1 to 3:1, and most preferably 2:1.

At this time, when the number of moles of the first metal is less than 0.1 based on the number of moles of the second metal being 1, the content of cerium and zirconium is lowered, and the ability to store and transfer oxygen in the air is lowered, thereby reducing the removal activity of volatile organic compounds. may be lowered, and when the number of moles of the first metal exceeds 10 based on the number of moles of the second metal being 1, the content of copper and silver may decrease, and thus the removal activity of volatile organic compounds at low temperature may be reduced.

According to one embodiment of the present invention, in the first metal, the molar ratio of cerium and zirconium may range from 1:99 to 99:1, preferably from 1:10 to 10:1, and more preferably from 1:10 to 10:1. It can be 1:1.

In this case, in the second metal, the molar ratio of copper to silver may be in the range of 1:99 to 99:1, preferably 1:10 to 10:1, and more preferably 1:1.

On the other hand, as the silver content increases, the volatile organic compound removal efficiency increases, but when the copper to silver molar ratio is 1:1, even if the silver content increases, the volatile organic compound removal efficiency does not significantly increase, so it is economical. Considering the phosphorus aspect, it is preferably included in a molar ratio of 1:1.

According to one embodiment of the present invention, the catalyst may operate at a temperature of 175 °C to 300 °C, preferably at a temperature of 200 °C to 300 °C. At this time, the action means to act as a catalyst in contact with ammonia for nitrogen conversion of ammonia.

Meanwhile, when the operating temperature of the non-platinum-based metal oxide catalyst for converting ammonia to nitrogen is less than 150° C. or less than 175° C. under moisture conditions, the activity of the catalyst may decrease. Also, conversion of ammonia to nitrogen oxide becomes dominant at high temperatures of 300°C or higher.

In addition, in the present invention, mixing an aqueous solution containing a cerium precursor, an aqueous solution containing a zirconium precursor, an aqueous solution containing a copper precursor, and an aqueous solution containing silver (step 1); Forming a precipitate by dropwise adding a basic solution to the aqueous solution mixed in step 1 (step 2); Aging the mixed aqueous solution containing the precipitate formed in step 2 (step 3); Preparing a non-platinum-based metal oxide catalyst for nitrogen conversion of ammonia of claim 1, including drying and calcining the precipitate in the mixed aqueous solution aged in step 3 (step 4); and contacting the prepared non-platinum metal oxide catalyst for nitrogen conversion of ammonia with ammonia.

According to one embodiment of the present invention, after performing step 3, washing the precipitate in the aged mixed aqueous solution may be further included.

Hereinafter, the method for converting ammonia to nitrogen according to the present invention will be described in detail for each step.

First, in the method for converting ammonia to nitrogen according to the present invention, step 1 is a step of mixing an aqueous solution containing a cerium precursor, an aqueous solution containing a zirconium precursor, an aqueous solution containing a copper precursor, and an aqueous solution containing a silver precursor.

The precursor of step 1 is preferably an acid salt compound selected from the group consisting of nitrate, sulfate, phosphate, hydrochloride and hydrofluoric acid, and may be in the form of nitrate as a preferred embodiment, but is not limited thereto.

Next, in the method for converting ammonia to nitrogen according to the present invention, step 2 is a step of forming a precipitate by dropwise adding a basic solution to the aqueous solution mixed in step 1.

The basic solution of step 2 may be aqueous sodium hydroxide solution or aqueous ammonia, which may be added dropwise and titrated to pH 10 or higher for co-precipitation. The content of the basic solution is not particularly limited, but when the pH is less than 10, mixtures in a salt state are non-uniformly precipitated, and some remain in an ionic state without precipitating, so catalyst productivity is reduced and a wastewater treatment process is required. There is a problem that the catalytic efficiency of the produced composite metal oxide catalyst is lowered.

Step 3 in the ammonia nitrogen conversion method according to the present invention is a step of aging the mixed aqueous solution containing the precipitate formed in step 2.

Aging in step 3 may be performed at a temperature of 60 ° C to 90 ° C for 1 hour to 48 hours, preferably at a temperature of 65 ° C to 85 ° C for 1 hour to 24 hours, more preferably may be performed for 2 hours at a temperature of 70 ° C to 80 ° C, but the aging temperature and time of step 3 are not limited thereto.

However, when the temperature of step 3 is performed at a low temperature of less than 60 ° C. for less than 1 hour, the reaction may not proceed sufficiently, which may affect the catalyst composition and crystallinity of the composite metal oxide.

Next, in the method for converting ammonia to nitrogen according to the present invention, step 4 is a step of drying and calcining the precipitate in the mixed aqueous solution aged in step 3.

Specifically, the drying temperature of step 4 is not particularly limited, but may be carried out at 50 ° C to 250 ° C, preferably 80 ° C to 200 ° C, more preferably 100 ° C to 150 ° C It may be performed at, most preferably at 110 ℃.

If the drying temperature is less than 50 ° C., there may be a problem that sufficient drying is not performed or the drying time is long, and if the drying temperature exceeds 250 ° C., there may be a problem that it must be performed at a high temperature.

The drying time of step 4 is not particularly limited, but may be performed for 1 hour to 48 hours, preferably 6 hours to 24 hours, and more preferably 10 hours to 15 hours. and most preferably for 12 hours.

When the drying time is less than 1 hour, sufficient drying is not achieved, and when the drying time exceeds 48 hours, there is a problem in that unnecessary time is increased.

In addition, the firing of step 4 may be performed by heating to a high temperature under an oxidizing atmosphere such as air or an oxygen-containing mixed gas.

The firing of step 4 may be performed at a temperature of 300 ° C to 600 ° C for 1 hour to 10 hours, preferably at a temperature of 320 ° C to 500 ° C for 2 hours to 8 hours, more preferably may be performed at a temperature of 350 ° C to 450 ° C for 3 hours to 6 hours, and most preferably at a temperature of 400 ° C for 4 hours. If the calcination in step 4 is performed at a temperature of less than 300 ° C, impurities are not sufficiently removed, resulting in a decrease in the removal efficiency of volatile organic compounds. There is a problem with deterioration.

Furthermore, the present invention provides a method for converting ammonia to nitrogen, comprising the step of contacting the prepared non-platinum-based metal oxide catalyst for nitrogen conversion of ammonia with ammonia.

Hereinafter, implementation examples and embodiments of the present invention will be described in detail so that those with general knowledge in the technical field to which the present application pertains can easily practice, as shown in the accompanying drawings, preferred embodiments of the present invention. In particular, the technical idea of the present invention and its core configuration and operation are not limited by this. In addition, the contents of the present invention can be implemented in various types of equipment, and is not limited to the implementation examples and examples described herein.

<Preparation Example 1> Preparation of a non-platinum metal oxide catalyst (CZCuAg) for nitrogen conversion of ammonia

10.7814 g of cerium nitrate (Ce(NO ₃ ) ₃ 6H2O, Sigma-Aldrich) was completely dissolved in ultrapure water to prepare an aqueous solution of cerium nitrate, and then 5.7412 g of zirconium nitrate (ZrO(NO ₃ ) ₂ .xH2O, Sigma-Aldrich) An aqueous solution of zirconium nitrate was prepared by completely dissolving in ultrapure water, and an aqueous solution of copper nitrate was prepared by completely dissolving 5.9986 g of copper nitrate (Cu(NO ₃ ) ₂ .3H2O, Sigma-Aldrich) in ultrapure water. In addition, a silver nitrate aqueous solution was prepared by completely dissolving 5.2177 g of silver nitrate (AgNO ₃ , Sigma-Aldrich) in ultrapure water.

Meanwhile, 40 g of caustic soda [NaOH, Sigma-Aldrich] was completely dissolved in 1 L of ultrapure water.

After mixing the prepared cerium nitrate aqueous solution, zirconium nitrate aqueous solution, copper nitrate aqueous solution, and silver nitrate aqueous solution, they are constantly stirred using a stirrer, and caustic soda aqueous solution is added until the pH reaches 10, followed by stirring for 18 hours, followed by ceria-zirconia-copper. - precipitated a silver mixture.

The ceria-zirconia-copper-silver precipitate was aged at 70-80° C. for 2 hours, then sufficiently washed with 6 L of hot ultrapure water and filtered. The filtered precipitate was dried at 110° C. for 12 hours and calcined at 400° C. for 4 hours to finally prepare a non-platinum metal oxide catalyst (CZCuAg) for converting ammonia to nitrogen.

<Production Example 2> Pt ₇ PD _One /Al ₂ O ₃ Preparation of Catalyst

Tetraammineplatinum(II) nitrate (Pt(NH ₃ ) ₄ ·(NO ₃ ) ₂ , Sigma-Aldrich) 0.39g, palladium nitrate (Pd(NO ₃ ) ₂ ·xH2O, Sigma-Aldrich) 0.06 g was completely dissolved in ultrapure water to prepare a mixed aqueous solution, which was mixed with gamma-aluminum oxide (gamma-Al ₂ O ₃ , Sigma-Aldrich).

The platinum-palladium-alumina mixture was dried at 100°C for 24 hours and then calcined at 500°C for 4 hours to finally prepare a Pt ₇ Pd ₁ /Al ₂ O ₃ catalyst.

<Preparation Example 3> Other Catalyst Ru/Al ₂ O ₃ , Ag/Al ₂ O ₃ , IrRu/Al ₂ O ₃ , Ir/Al ₂ O ₃ manufacturing method

Ruthenium nitrosyl nitrate (Ru(NO)(NO ₃ ) ₃ , Sigma-Aldrich), silver nitrate (AgNO ₃ , Sigma-Aldrich), iridium chloride were added to gamma-aluminum oxide in the same manner as in Preparation Example 2. (III) (IrCl ₃ ·xH ₂ O, Sigma-Aldrich) was used to prepare a metal weight ratio of 1.5%.

<Experimental Example 1> CZCuAg catalyst and Pt ₇ PD _One /Al ₂ O ₃ Evaluation of nitrogen conversion performance of ammonia of catalyst

Experiment conditions Pt ₇ Pd ₁ /Al ₂ O ₃ CZCuAg catalytic amount 0.2cc total flow 333ml/min space speed 100,000 hours ^-1 Pretreatment 400℃ 10% H ₂ /He 1h 400℃ 10% O ₂ /He 1h reactive gas 2000 ppm NH ₃ , 10% O ₂ , He bal.

1 shows test conditions _for nitrogen _{conversion of} ammonia using a catalyst according to an embodiment of the present invention and the _conversion rate accordingly. Under the conditions of 1, FT-IR analysis equipment was used. The temperature range was set at 50 ° C intervals from 100 ° C to 500 ° C, and the ammonia conversion performance at each temperature was confirmed by maintaining the temperature for 30 minutes. The Pt ₇ Pd ₁ /Al ₂ O ₃ catalyst showed 100% conversion at 200 °C and 92% conversion at 250 °C or higher, and the CZCuAg catalyst showed 57% conversion at 150 °C, 93% conversion at 200 °C, and 250 °C or higher. showed 92% conversion rate.

<Experimental Example 2> CZCuAg catalyst and Pt ₇ PD _One /Al ₂ O ₃ Evaluation of catalyst conversion of ammonia to nitrogen

*

Figure 2 shows test conditions and results for nitrogen conversion of ammonia using a Pt ₇ Pd ₁ /Al ₂ O ₃ catalyst, which is an embodiment of the present invention, and Figure 3 shows nitrogen of ammonia using a CZCuAg catalyst, which is an embodiment of the present invention. Conversion test conditions and results are shown. It was carried out under the same conditions as Experimental Example 1, and MS analysis equipment was used.

2, in the case of the Pt ₇ Pd ₁ /Al ₂ O ₃ catalyst, it was confirmed that the ammonia conversion to nitrogen reaction occurred for the first time at 200 °C. It was confirmed that the ion current of NH ₃ (17 m/z) decreased. In addition, it was confirmed that N ₂ O, NO, and N ₂ were formed in large numbers in the order of products in the above reaction.

In the case of the CZCuAg catalyst in FIG. 3, it was confirmed that the reaction of ammonia to nitrogen conversion occurs for the first time at 150 ° C. In the above reaction, it was confirmed that NO, N ₂ O, and N ₂ were formed in large numbers in the order of products.

<Experimental Example 3> Comparative test of nitrogen conversion of ammonia according to temperature with respect to the type of catalyst

Experiment conditions Pt ₇ Pd ₁ /A CZCuAg Ru/A Ag/A IR/A Ir/A catalytic amount 0.2cc total flow 333ml/min space speed 100,000 hours ^-1 Pretreatment 400℃ 10% H ₂ /He 1h 400℃ 10% O ₂ /He 1h 450℃ 10% H ₂ /He 1h reactive gas 2000 ppm NH ₃ , 10% O ₂ , He bal.

Figure 4 shows the results of comparing the nitrogen conversion rate of ammonia according to the temperature with respect to the type of catalyst, which is an embodiment of the present invention. FT-IR analysis equipment was used under the conditions of Table 2 above. Compared to other catalysts, the CZCuAg catalyst showed an ammonia conversion rate of 57% from 150 °C. In addition to the Pt ₇ Pd ₁ /Al ₂ O ₃ catalysts presented as comparative groups in FIGS. 1 and 2, Ru/Al ₂ O ₃ , Ag/Al ₂ O ₃ , IrRu/Al ₂ O ₃ , and Ir/Al ₂ O ₃ catalysts All of them showed low ammonia conversion at 150 ° C. Through this, it was confirmed that the ammonia nitrogen conversion reaction of the CZCuAg catalyst showed a higher conversion rate at a lower temperature than the other comparative catalysts.

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<Experimental Example 4> Comparative test of nitrogen conversion and nitrogen selectivity of ammonia according to temperature with respect to the type of catalyst under moisture conditions

Experiment conditions Pt ₇ Pd ₁ /A Ir/A IR/A Ru/A Ag/A CZCuAg catalytic amount 0.2cc total flow 333ml/min space speed 100,000 hours ^-1 Pretreatment 450℃ 10% H ₂ /He 1h 450℃ 21% O ₂ /He 1h reactive gas 2000 ppm NH ₃ , 21% O ₂ , 2.5% H ₂ O He bal.

Figure 5 shows the results of comparing the nitrogen conversion rate of ammonia according to the temperature with respect to the type of catalyst under the moisture condition, which is an embodiment of the present invention, Figure 6 shows the temperature for the type of catalyst under the moisture condition, which is an embodiment of the present invention It shows the result of comparing the selectivity of nitrogen according to. FT-IR analysis equipment was used under the conditions of Table 3 above.

According to FIG. 5, in the case of the CZCuAg catalyst in the moisture condition, the ammonia conversion rate was 44% at 175 ° C and 90% at 200 ° C. The comparative group, the Ir/Al ₂ O ₃ catalyst, showed an ammonia conversion rate of 41% at 175°C and 77% at 200°C. The Pt ₇ Pd ₁ /Al ₂ O ₃ catalyst presented as a comparative group in FIGS. 1 and 2 showed an ammonia conversion rate of 8% at 175°C and 69% at 200°C. Through this, it was confirmed that the ammonia nitrogen conversion reaction of the CZCuAg catalyst showed a higher conversion rate at a lower temperature than the other comparative catalysts even under moisture conditions.

In FIG. 6, the CZCuAg catalyst exhibited nitrogen selectivities of 15% at 175°C, 74% at 200°C, and 86% at 250°C. The Pt ₇ Pd ₁ /Al ₂ O ₃ catalyst presented as a comparative group in FIGS. 1 and 2 showed low nitrogen selectivity of 0% at 175°C, 19% at 200°C, and 57% at 250°C. The comparative Ir/Al ₂ O ₃ catalyst exhibited nitrogen selectivities of 40% at 175°C, 43% at 200°C, and 40% at 250°C.

5 and 6, it was confirmed that the CZCuAg catalyst had higher ammonia nitrogen conversion and higher nitrogen selectivity than other catalysts at 175° C. to 300° C. under moisture conditions.

Claims (10)

A non-platinum metal oxide catalyst containing cerium (Ce), zirconium (Zr), copper (Cu) and silver (Ag),
A non-platinum metal oxide for nitrogen conversion of ammonia, characterized in that the molar ratio of a first metal composed of cerium and zirconium and a second metal composed of copper and silver is 1:1 to 3:1, and the molar ratio of copper/silver is 7 or less. catalyst. The method of claim 1,
The catalyst is a non-platinum metal oxide catalyst for nitrogen conversion of ammonia, characterized in that it acts at a temperature of 175 ℃ to 300 ℃. mixing an aqueous solution containing a cerium precursor, an aqueous solution containing a zirconium precursor, an aqueous solution containing a copper precursor, and an aqueous solution containing silver (step 1);
Forming a precipitate by dropwise adding a basic solution to the aqueous solution mixed in step 1 (step 2);
Aging the mixed aqueous solution containing the precipitate formed in step 2 (step 3);
Preparing a non-platinum-based metal oxide catalyst for nitrogen conversion of ammonia of claim 1, including drying and calcining the precipitate in the mixed aqueous solution aged in step 3 (step 4); and
A method for converting ammonia to nitrogen comprising the step of contacting the prepared non-platinum metal oxide catalyst for nitrogen conversion of ammonia with ammonia. The method of claim 3,
After performing step 3, a method for converting ammonia into nitrogen, characterized in that it further comprises the step of washing the precipitate in the aged mixed aqueous solution with water. The method of claim 3,
The precursor of step 1 is a nitrogen conversion method of ammonia, characterized in that the acid salt compound selected from the group consisting of nitrate, sulfate, phosphate, hydrochloride and hydrofluoric acid. The method of claim 3,
The basic solution of step 2 is an aqueous solution of sodium hydroxide or aqueous ammonia, which is added dropwise and titrated to pH 10 or higher to co-precipitate. The method of claim 3,
The aging of step 3 is a nitrogen conversion method of ammonia, characterized in that carried out for 1 hour to 48 hours at a temperature of 60 ℃ to 90 ℃. The method of claim 3,
The drying of step 4 is a method for converting ammonia to nitrogen, characterized in that carried out at 50 ℃ to 250 ℃ for 1 hour to 48 hours. The method of claim 3,
The calcination of step 4 is a nitrogen conversion method of ammonia, characterized in that carried out for 1 hour to 10 hours at a temperature of 300 ℃ to 600 ℃. The method of claim 3,
The step of contacting the catalyst with ammonia is a method for converting ammonia to nitrogen, characterized in that carried out at a temperature of 175 ℃ to 300 ℃.

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