KR20200033024A - Selective oxidation catalyst for converting gaseous ammonia into nitrogen and its production method - Google Patents

Abstract

The present invention relates to a selective oxidation catalyst for selectively oxidizing gaseous ammonia as a reactant to nitrogen as a product, and a method for producing the same. The oxidization catalyst: has a carrier containing titania as a main component and a predetermined noble metal as an active metal; and can be produced by using a composite carrier after selectively and preferentially supporting metal oxide as a cocatalyst on the titania carrier and controlling the firing conditions. The present invention: provides the selective oxidation catalyst of ammonia with excellent ammonia removal efficiency and selectivity to nitrogen by controlling the firing conditions after supporting ruthenium of a predetermined amount on a titania carrier; and more increase the function of active metal to greatly improve low temperature activity at 200 to 300°C when using a composite carrier by preferentially supporting metal oxide such as vanadium, tungsten, phosphorus, or yttrium and the like as a cocatalyst on the titania carrier and controlling the firing conditions unlike conventional methods of supporting an active metal component on a simple titania carrier. In addition, a part of NO_x can be removed by reacting with ammonia under conditions in which nitrogen oxide and ammonia enter at the same time when using the oxidation catalyst.

Description

Selective oxidation catalyst for converting gaseous ammonia to nitrogen and its manufacturing method {SELECTIVE OXIDATION CATALYST FOR CONVERTING GASEOUS AMMONIA INTO NITROGEN AND ITS PRODUCTION METHOD}

The present invention relates to a selective oxidizing catalyst for selectively oxidizing gaseous ammonia as a reactant to nitrogen as a product, and a method for preparing the same, and the catalyst and a method for the preparation are related to promoting a selective oxidation reaction for ammonia.

Recently, along with continuous industrial development and economic growth, energy consumption has skyrocketed. Accordingly, the problem of environmental pollution is seriously raised. Among them, air pollution is not only a diverse source, but also a limited local problem in the region where the source is located. Because it can give, it is subject to international regulation. Among various air pollutants, ammonia is an odor-inducing substance that causes discomfort even at low concentrations. When directly exposed to the human body, irritation occurs to the eyes, nose, and skin, and when the concentration of ammonia is high, it can cause disorders in the respiratory system. In addition, in the case of ultra-fine dust (PM2.5), which is a recent problem, ammonia emitted from various industrial facilities and automobiles is generated by reacting with sulfur dioxide or nitrogen oxide when it behaves in the air. When the generated ultrafine dust is absorbed into the human body, it may cause conjunctivitis, rhinitis, asthma, alveolar damage, and the like. In addition, ammonia in the flue gas appears corrosive when it is present with moisture, which adversely affects industrial facilities and animals and plants. In particular, when coexisting with the sulfur dioxide (SO ₂ ) component in the flue gas, salts such as ammonium sulfate and ammonium bisulfate are generated, and thus there is a problem in the process of clogging and corrosion in the process. However, for nitrogen compounds such as ammonia, the development of treatment technology is significantly lower than its importance. Currently, ammonia is discharged from various chemical facilities using urea as a raw material, and it is also contained in a large amount in wastewater. In addition, it is also included in the exhaust gas of 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, a biological treatment method, an adsorption method, an incineration method, a catalytic oxidation method using a catalyst, etc. are used as an ammonia treatment technique to satisfy ammonia emission limit values. However, in the case of biological treatment, there is a disadvantage in that periodic microorganisms need to be managed and temperature-sensitive, and thus the treatment ability is affected depending on the season. In the case of the adsorption method, a high concentration of ammonia treatment is difficult, and an additional cost for the treatment of the adsorbent occurs . On the other hand, the selective oxidation reaction of ammonia using a catalyst is spotlighted as the most efficient ammonia treatment technology in economical or environmental aspects.

On the other hand, the selective catalytic oxidation reaction should ideally be mainly a reaction in which ammonia reacts with oxygen and is directly oxidized to nitrogen harmless to the human body as shown in [Reaction Scheme 1] below, but in most cases, ammonia is nitrogen monoxide as in [Reaction Scheme 2] , It is very important to suppress this reaction because it has the disadvantage of being oxidized to other nitrogen oxides such as nitrogen dioxide, nitrous oxide, and the like to generate secondary pollutants. Accordingly, various studies have been actively conducted to solve these problems.

[Scheme 1]

4NH ₃ + 3O ₂ → 2N ₂ + 6H ₂ O

[Scheme 2]

4NH ₃ + 5O ₂ → 4NO + 6H ₂ O

4NH ₃ + 7O ₂ → 4NO ₂ + 6H ₂ O

2NH ₃ + 2O ₂ → N ₂ O + 6H ₂ O

Specifically, an example of a selective oxidation catalyst for converting gaseous ammonia to nitrogen is disclosed in Korean Patent Publication No. 10-2007-0112201. According to the published patent, ammonia may be treated at a temperature between 300 ° C and 500 ° C, but despite the presence of a high content of 13 wt% of vanadium as the active metal in the titania carrier, it is as low as 20% at a low temperature of 300 ° C. Ammonia conversion and nitrogen selectivity. In addition, another example of a catalyst for removing ammonia is disclosed in Korean Patent Publication No. 10-2012-0128029, and according to the published patent, a conversion rate of ammonia conversion of 90% or higher and a conversion rate of nitrogen of 75% or higher at 340 to 450 ° C Although shown, a high reaction temperature of 340 ° C or higher is required.

Accordingly, the recent trend of research on the oxidation catalyst for removing gaseous ammonia is that it has excellent ammonia conversion rate and conversion rate to nitrogen by using a precious metal series such as platinum, palladium, rhodium, etc. as an active metal at a low reaction temperature of 200 ~ 300 ℃. Although research is ongoing, in the case of an ammonia oxidation catalyst using an active metal as a noble metal, the problem that most of the removed ammonia is converted into nitrogen oxides (NO, NO ₂ , N ₂ O) still exists. In order to solve this, in Korean Patent Publication No. 10-2011-0086720 and Non-Patent Document 1 (Applied Surface Science, 402, pp. 323-329, 2017), a catalyst using an active metal as a noble metal is reacted with a non-noble metal-based material. Technology has been attempted to increase the ammonia conversion rate and selectivity to nitrogen through mixing, but it does not exhibit a satisfactory effect in relation to the ammonia conversion rate and selectivity to nitrogen at 300 ° C or lower.

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

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

The present invention is to solve the problems of the prior art, the object of the present invention is added to the ammonia contained in various chemical processes such as coal-fired power plant, fertilizer manufacturing process, petroleum refinery process, wastewater treatment facility or contained in the vehicle exhaust gas It is to provide a selective oxidation catalyst having excellent ammonia conversion rate and selectivity to nitrogen in a low temperature region of 200 to 300 ° C even without heat supply and a method for manufacturing the same.

In the process of researching and developing a catalyst related to the above-mentioned solution, the present inventors, as a selective oxidation catalyst of ammonia for oxidizing ammonia to nitrogen, use a carrier mainly composed of titania and a predetermined noble metal as an active metal, but the firing conditions While having a good ammonia conversion rate by controlling the, while selectively using a metal oxide as a co-catalyst on the titania carrier preferentially to control the firing conditions, when using a composite carrier, the function of the active metal is further enhanced. It was confirmed that the low-temperature activity at 200 to 300 ° C was greatly improved, and the present invention was reached. The gist of the present invention, based on the perceptions and knowledge of the above-mentioned solutions, is the same as described in the claims.

(1) An oxidation catalyst for removing ammonia using a carrier containing titania as a main component and ruthenium as an active metal, wherein the ruthenium is supported in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the carrier, an oxidation catalyst for removing ammonia .

(2) RuO ₂ surface density is controlled to 0.6nm ^-2 or less, the oxidation catalyst for removing ammonia in (1) above.

(3) The carrier further comprises any one metal selected from 2 parts by weight of vanadium, 2 parts by weight of tungsten, 0.5 parts by weight of phosphorus, or 0.2 parts by weight of yttrium based on 100 parts by weight of titania, and the metal is before the ruthenium loading. An oxidation catalyst for removing ammonia of (1) or (2), characterized in that it is previously supported on titania.

(4) A method for preparing an oxidation catalyst for removing ammonia, characterized in that it is prepared by supporting a ruthenium precursor so that it is 1 to 5 parts by weight of ruthenium, and calcining at 300 to 700 ° C, relative to 100 parts by weight of a carrier containing titania as a main component.

(5) The ruthenium precursor is ruthenium nitrosyl nitrate (Ru (NO) (NO ₃ ) ₃ ), ruthenium chloride (RuCl ₃ ), ruthenium acetylacetonate (Ru (acac) ₃ ), ruthenium chloride hydrate (RuCl3 xH ₂ O) the oxidation catalyst production method for removing ammonia, characterized in that at least one selected from the group consisting of (4).

(6) The carrier is first loaded with an oxide precursor for any metal selected from 2 parts by weight of vanadium, 2 parts by weight of tungsten, 0.5 parts by weight of phosphorus, or 0.2 parts by weight of yttrium based on 100 parts by weight of titania, followed by firing. Method for producing an oxidation catalyst for removing ammonia in (4), further comprising.

(7) The method for producing an oxidation catalyst for removing ammonia according to (6), wherein the oxide precursor supported on the titania is calcined at 400 to 600 ° C.

(8) The oxide precursor for vanadium is ammonium-methanadate (NH ₄ VO ₃ ) or vanadium oxide (V ₂ O ₅ ) characterized in that the method for producing an oxidation catalyst for removing ammonia in (6).

(9) The oxide precursor for tungsten is ammonium-tungstate ((NH ₄ ) ₁₀ H ₂ (W ₂ O ₇ ) ₆ ) or tungsten oxide (WO ₃ ) for removing ammonia of (6). Oxidation catalyst manufacturing method.

(10) The oxide precursor for phosphorus is ammonium-dihydrogen phosphate (H ₆ NO ₄ P) or phosphoric acid (H ₃ PO ₄ ), characterized in that the production method of the oxidation catalyst for removing ammonia (6).

(11) The yttrium oxide precursor is yttrium-nitrate hexahydrate (Y (NO ₃ ) ₃ 6H ₂ O), characterized in that the production method of the oxidation catalyst for removing ammonia in (6).

(12) The oxidation catalyst for removing ammonia according to any one of (4) to (6), characterized in that the oxidation catalyst is processed in any one form selected from the group consisting of particles, monoliths, slates and pellets. Manufacturing method.

According to the present invention, it is possible to provide a selective oxidation catalyst for ammonia having excellent ammonia removal efficiency and selectivity to nitrogen by controlling ruination conditions by supporting ruthenium in a predetermined amount on a titania carrier.

In addition, unlike the conventional method of supporting an active metal component on a simple titania carrier, a metal carrier such as vanadium, tungsten, phosphorus or yttrium is preferentially supported as a cocatalyst on the titania carrier to control the firing conditions to control the composite carrier. When used, the function of the active metal is further enhanced, and in particular, low-temperature activity at 200 to 300 ° C can be greatly improved.

In addition, it is possible to provide a method of removing nitrogen oxides by reacting nitrogen oxides with ammonia as a reducing agent by using a selective oxidation catalyst of ammonia prepared according to the present invention. That is, a selective oxidation catalyst for removing ammonia, ruthenium / titania or ruthenium / metal (oxide) / titania catalyst may be removed by reacting some NOx with ammonia in a condition where nitrogen oxide and ammonia enter at the same time.

1 is a RuO ₂ surface density (RuO ₂ / nm ² according to the calcination temperature of the ruthenium / titania catalyst used in Preparation Examples 1, 5, 6, and 7, 8 of the present invention and physical properties of titania used as a carrier. ) Is a graph showing the correlation between nitrogen yield and ammonia converted to nitrogen.

Hereinafter, preferred embodiments of the present invention will be described in detail. In the description of the present invention, when it is determined that the detailed description of the related known technology may obscure the subject matter of the present invention, the detailed description will be omitted. Throughout the specification, when a part “includes” a certain component, it means that it may include other components, not exclude other components, unless specifically stated otherwise.

The oxidation catalyst for removing ammonia according to the present invention is basically an oxidation catalyst for removing ammonia using a carrier as a main component of titania and ruthenium as an active metal, wherein the ruthenium is supported in 1 to 5 parts by weight based on 100 parts by weight of the carrier Characterized in that, such a catalyst can be prepared by sequentially supporting, drying and calcining a ruthenium precursor on a titania carrier.

First, the loading process may be performed using an impregnation method as a method for supporting ruthenium as an active metal on titania as a support. Specifically, the ruthenium precursor is quantified based on the weight of the prepared titania carrier, dissolved in an aqueous solution, and sufficiently mixed with the prepared titania carrier to prepare a slurry.

The ruthenium precursor may be at least one selected from the group consisting of ruthenium nitrosyl nitrate (Ru (NO) (NO ₃ ) ₃ ), ruthenium chloride (RuCl ₃ ), and ruthenium chloride hydrate (RuCl ₃ xH ₂ O). . However, it is not particularly limited as long as it does not impair the ammonia conversion rate and selectivity to nitrogen of the catalyst to be finally produced in a preferred ruthenium content range to be described later. In this case, the selectivity to nitrogen means that the generation of direct oxides is suppressed.

The content of the supported ruthenium is preferably 0.1 to 5 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of the titania carrier on a ruthenium element basis. If the ruthenium content is less than 0.1 parts by weight, sufficient catalytic activity cannot be achieved, and if the ruthenium content is more than 5 parts by weight, the ammonia conversion rate increases, but the conversion rate or selectivity to nitrogen decreases. It is not desirable in developing.

Next, after the moisture of the prepared slurry is removed using a rotary vacuum evaporator, it is sufficiently dried for at least 24 hours at a temperature of 100 to 105 ° C using a dryer to remove residual moisture contained in the fine pores in the slurry.

Subsequently, the dried sample is subjected to a calcination process to control the size, dispersion degree and surface density of the active metal through heat treatment. In particular, in the firing process, it is preferable that the surface density of RuO ₂ is controlled to 0.6 nm ⁻² or less in order to improve ammonia conversion and selectivity to nitrogen through control of the process conditions. To this end, the firing process is preferably performed for 1 to 10 hours at a temperature of 300 to 700 ° C. in a gas atmosphere containing nitrogen and oxygen, most preferably 4 hours. The firing process may be performed in various types of known furnaces, such as a convection type furnace, a tube type furnace, and a grate type furnace, and is not particularly limited.

On the other hand, in the present invention, in particular, in order to improve the low-temperature activity of the catalyst at 200 to 300 ° C, it is characterized by using a complex carrier prepared by preferentially supporting a metal oxide on a titania carrier before carrying a ruthenium active metal. do.

The metal oxide related to the low temperature activity of the oxidation catalyst functions as a co-catalyst, and its type and content are selected from 2 parts by weight of vanadium, 2 parts by weight of tungsten, 0.5 parts by weight of phosphorus, or 0.2 parts by weight of yttrium. It is preferably an oxide for any one metal. The composite carrier is made separately before carrying the ruthenium, which is an active metal, and can be prepared by sequentially supporting each metal oxide precursor, followed by drying and firing. In this case, the firing conditions with respect to temperature and time when manufacturing the composite carrier may be changed in consideration of the properties of each supported metal oxide, and the firing temperature is controlled in the range of 400 to 600 ° C. from the viewpoint of enhancing the low temperature activity of the catalyst. desirable.

The metal oxide precursor is not particularly limited as long as it does not lower the ammonia conversion rate and selectivity to nitrogen of the catalyst to be produced. Specifically, ammonium-metavanadate (NH ₄ VO ₃ ), vanadium oxide (V ₂ O ₅ ), etc. may be selected as the vanadium precursor, and ammonium-meta-tungstate ((NH ₄ ) ₁₀ as the tungsten precursor. H ₂ (W ₂ O ₇ ) ₆ ), tungsten oxide (WO ₃ ), etc. may be selected, and as the phosphorus precursor, ammonium-dihydrogenphosphate (NH ₄ H ₂ PO ₄ ), phosphoric acid (H ₃ PO ₄ ) may be selected, and yttrium-nitrate hexahydrate (Y (NO ₃ ) ₃ 6H ₂ O) may be selected as the yttrium precursor.

On the other hand, when the selective oxidation catalyst of ammonia according to the present invention is actually applied, it can be used by coating on structures such as honeycomb, metal fiber, metal plate, metal foam, and ceramic filter.

As described above, the selective oxidation catalyst of ammonia prepared according to the present invention suppresses oxidation of ammonia in flue gas to nitrogen oxides, and at the same time, selectively oxidizes to nitrogen, which exhibits high conversion efficiency at low temperatures of 200 to 300 ° C or less. It can be induced. In addition, it can be used to remove nitrogen oxides by reacting nitrogen oxides with ammonia and oxygen by using a selective oxidation catalyst of ammonia according to the present invention.

Hereinafter, the present invention will be described in more detail based on preferred examples and experimental examples of the present invention. However, the technical spirit of the present invention is not limited to or limited thereto, and can be variously implemented by a person skilled in the art.

Preparation Example 1

In the production of a selective oxidation catalyst for ammonia according to the present invention, 1 part by weight based on 100 parts by weight of titania used as a carrier by selecting ruthenium nitrosyl nitrate (Ru (NO) (NO ₃ ) ₃ ) as a ruthenium precursor Quantify to be (based on ruthenium element) and dissolve in distilled water at room temperature. Thereafter, a ruthenium aqueous solution was added to a prepared titania (specific surface area 300 m ² / g, crystal size 122 mm 2) carrier and mixed to prepare a slurry, followed by stirring and heating at 65 ° C. using a rotary vacuum evaporator to evaporate moisture, and fine In order to completely remove the moisture contained in the pores, it is dried in a dryer at a temperature of 105 ° C for 24 hours or more. Thereafter, in a gas atmosphere containing nitrogen and oxygen, it was maintained at a temperature of 400 ° C. and fired for 4 hours to prepare a catalyst.

Preparation Example 2

A ruthenium / titania catalyst was prepared in the same manner as in Production Example 1, except that the ruthenium content in Production Example 1 was determined to be 0.1 parts by weight.

Preparation Example 3

A ruthenium / titania catalyst was prepared in the same manner as in Production Example 1, except that the ruthenium content in Production Example 1 was determined to be 0.5 parts by weight.

Preparation Example 4

A ruthenium / titania catalyst was prepared in the same manner as in Production Example 1, except that the ruthenium content in Production Example 1 was determined to be 5 parts by weight.

Preparation Example 5

A ruthenium / titania catalyst was prepared in the same manner as in Production Example 1, except that the firing temperature in Production Example 1 was maintained at 500 ° C.

Preparation Example 6

A ruthenium / titania catalyst was prepared in the same manner as in Production Example 1, except that the firing temperature in Production Example 1 was maintained at 600 ° C.

Preparation Example 7

A ruthenium / titania catalyst was prepared in the same manner as in Preparation Example 1, except that a titania carrier having a titania (specific surface area of 76.6 m ² / g, crystal size of 206 mm ² ) used as a carrier in Preparation Example 1 was used.

Preparation Example 8

A ruthenium / titania catalyst was prepared in the same manner as in Production Example 1, except that a titania carrier having a titania (specific surface area of 258.88 m ² / g, crystal size of 128 mm ² ) used as a carrier in Preparation Example 1 was used.

Preparation Example 9

The vanadium precursor is 2 parts by weight (based on the element of vanadium) and the amount of vanadium precursor is determined by quantifying 2 parts by weight (based on the element of vanadium) with respect to 100 parts by weight of titania (specific surface area 300 m ² / g, crystal size: 122 mm 2) used as a carrier by selecting ammonium-metavanadate as the vanadium precursor. Add and mix. Thereafter, the drying process was prepared in the same manner as in Preparation Example 1, and maintained at a temperature of 400 ° C. in a gas atmosphere containing nitrogen and oxygen, followed by firing for 4 hours to prepare a catalyst. Subsequently, 1 part by weight of ruthenium precursor (based on ruthenium element) was quantitatively charged and mixed, and the drying and firing process was performed in the same manner as in Preparation Example 1 to prepare a ruthenium / vanadium / titania catalyst.

Preparation Example 10

Tungsten precursor is quantified in 2 parts by weight (based on tungsten element) with respect to 100 parts by weight of titania (specific surface area: 300 m ² / g, crystal size: 122 mm 2) used as a carrier by selecting ammonium-methung tungstate as the tungsten precursor. Add and mix. Thereafter, the drying process was prepared in the same manner as in Preparation Example 1, and maintained at a temperature of 600 ° C. in a gas atmosphere containing nitrogen and oxygen, followed by firing for 4 hours to prepare a catalyst. Thereafter, 1 part by weight of ruthenium precursor (based on ruthenium element) was quantitatively added to the prepared tungsten / titania catalyst, and the drying and calcination process was performed in the same manner as in Preparation Example 1 to prepare a ruthenium / tungsten / titania catalyst.

Preparation Example 11

Phosphorus precursor is 0.5 parts by weight (based on phosphorus element) and 100 parts by weight of titania (specific surface area 300m ² / g, crystal size 122Å) used as a carrier by selecting ammonium-dihydrogenphosphate as the phosphorus precursor. Put in and mix. Thereafter, the drying process was prepared in the same manner as in Preparation Example 1, and maintained at a temperature of 400 ° C. in a gas atmosphere containing nitrogen and oxygen, followed by firing for 4 hours to prepare a catalyst. The ruthenium precursor was then added to the prepared phosphorus / titania catalyst by quantifying 1 part by weight (based on ruthenium element), and the drying and calcination process was performed in the same manner as in Preparation Example 1 to prepare a ruthenium / phosphorus / titania catalyst.

Preparation Example 12

The yttrium precursor is 0.2 parts by weight (based on yttrium element), and the yttrium carrier is quantified based on 100 parts by weight of titania (specific surface area 300 m ² / g, crystal size 122 mm 2) used as a carrier by selecting yttrium-nitrate hexahydrate as the yttrium precursor. Put in and mix. Thereafter, the drying process was prepared in the same manner as in Preparation Example 1, and maintained at a temperature of 400 ° C. in a gas atmosphere containing nitrogen and oxygen, followed by firing for 4 hours to prepare a catalyst. Thereafter, 1 part by weight of ruthenium precursor (based on ruthenium element) was quantitatively added to the prepared yttrium / titania catalyst, and the drying and calcination process was performed in the same manner as in Production Example 1 to prepare a ruthenium / yttrium / titania catalyst.

The catalyst composition and firing temperature according to the above preparation examples are shown in Table 1 below.

division carrier Active substance (parts by weight) Firing temperature
(℃) ruthenium vanadium tungsten sign yttrium Preparation Example 1 Titania A One 400 Preparation Example 2 Titania A 0.1 400 Preparation Example 3 Titania A 0.5 400 Preparation Example 4 Titania A 5 400 Preparation Example 5 Titania A One 500 Preparation Example 6 Titania A One 600 Preparation Example 7 Titania B One 400 Preparation Example 8 Titania C One 400 Preparation Example 9 Titania A One 2 400
400 Preparation Example 10 Titania A One 2 600400 Preparation Example 11 Titania A One 0.5 400400 Preparation Example 12 Titania A One 0.2 400400 *week
-Titania A: specific surface area 344.7m ² / g, crystal size 112Å
-Titania B: specific surface area 76.6m ² / g, crystal size 206Å
-Titania C: specific surface area 258.88m ² / g, crystal size 128Å

Example 1

Selective oxidation experiments of ammonia were performed on the ruthenium / titania catalyst prepared according to the content of ruthenium used as an active material in the titania carrier according to Preparation Examples 1 to 2,3,4 , and the conversion of ammonia and the conversion rate to nitrogen Measurement was made, and the results are shown in Table 2 below. The experimental conditions and measurement conditions are as follows.

 [Experimental conditions]

The temperature range of the catalytic reactor was fixed at 200 to 400 ° C, and the gas to be injected was a mixed gas containing 200 ppm of ammonia, 10 mol% of oxygen, and 6 mol% of moisture under a nitrogen (N2) atmosphere, and the space velocity was 60,000 hr. ^It was kept at ^-1 . The space velocity is an index indicating the amount of gas to be treated by the catalyst and is expressed as a ratio of the amount of catalyst (volume) to the total gas flow rate (volume). For example, if the space velocity is large, it means that the amount of processing gas per unit volume of the catalyst is large.

[How to measure]

The conversion of ammonia and conversion to nitrogen were calculated according to the following Equations 1 and 2. Here, since the nitrogen selectivity among the methods for evaluating the performance of ammonia being converted to nitrogen means the degree of conversion to nitrogen among the total ammonia converted, it is limited to represent nitrogen generated by oxidation of ammonia by itself. In this example, it was calculated as the nitrogen yield converted to nitrogen in ammonia injected into the reactor during the catalytic reaction. In addition, the concentration of nitrogen oxides (NO, NO ₂ , N ₂ O) generated by oxidation of ammonia injected into the reactor was calculated by measuring with a non-dispersive infrared gas analyzer.

division Ammonia conversion rate (%) Nitrogen yield (%) Preparation Example 1 85 65.3 Preparation Example 2 0 0 Preparation Example 3 50 43.8 Preparation Example 4 100 44.5 *week
Measured at a reaction temperature of 250 ° C.

Referring to Table 2, it was found that the selective oxidation efficiency of ammonia shows a large difference as the active material ruthenium is supported on titania used as a carrier according to the content. That is, as the ruthenium content applied when preparing the ruthenium / titania catalyst as an ammonia oxidation catalyst increased, the ammonia conversion rate tended to increase, but the conversion rate to nitrogen was 1 part by weight based on 100 parts by weight of titania used as a carrier (ruthenium element Criterion). Therefore, it can be seen that the content of ruthenium when preparing a ruthenium / titania catalyst with an ammonia oxidation catalyst having excellent ammonia conversion and conversion to nitrogen is most suitable when 1 part by weight (based on ruthenium element) with respect to 100 parts by weight of titania. However, when the content of ruthenium is supported by 1 part by weight (based on ruthenium element) or less by weight of 100 parts by weight of titania, there is a disadvantage that the conversion rate of ammonia is low, but the conversion rate to nitrogen is excellent, and the content of ruthenium is 100 parts by weight of titania With respect to 1 part by weight (based on ruthenium element), the conversion rate to nitrogen is reduced, but the ammonia conversion rate has the advantage of exhibiting high activity up to a lower temperature. It can be included in the scope of the present invention.

Example 2

When preparing a ruthenium / titania catalyst, RuO ₂ dispersed on the surface is affected by the calcination temperature of the catalyst and the physical properties of titania used as a carrier. For this reason, there was applied by introducing the concept of a surface density in the RuO ₂ considering the surface area of the catalyst _{(RuO 2 surface density, Ns)} . The surface density of RuO ₂ can be calculated by the following equation.

Here, Cw is the ruthenium content (g / g) of the catalyst, NA is the avogadro number (6.022 × 10 ²³ / mol), Mw is the molecular weight of ruthenium (101.1), and S _BET is the specific surface area of the catalyst (m ² / g). Therefore, in order to evaluate the effect of the surface density of RuO ₂ on the selective oxidation properties of ammonia according to the calcination temperature of the ruthenium / titania catalyst and the physical properties of titania used as a carrier, Preparation Examples 1, 5, 6 and Preparation Example 7, A ruthenium / titania catalyst was prepared according to 8 to perform a selective oxidation experiment, and ammonia conversion and nitrogen yield were measured, and the results are shown in Table 3 below. Experimental and measurement methods are the same as in Example 1. In addition, the correlation between the surface density of RuO ₂ and the ammonia conversion rate according to the calcination temperature of the ruthenium / titania catalyst and the physical properties of titania used as a carrier is schematically shown in FIG. 1 (correlation with ruthenium surface density).

division Ammonia conversion rate (%) Nitrogen yield (%) Surface density
(RuO ₂ / nm ² ) Preparation Example 1 85 65.3 0.5222 Preparation Example 5 65 49.8 0.6559 Preparation Example 6 40 35.1 1.3213 Preparation Example 7 55 47.4 1.5012 Preparation Example 8 0 0 2.0812 *week
Measured at a reaction temperature of 250 ° C.

Referring to Table 3 and Figure 1, it was found that the selective oxidation efficiency of ammonia shows a large difference according to the surface density of ruthenium. That is, it was confirmed that the ammonia conversion rate increased as the ruthenium surface density decreased, and the catalyst with excellent ammonia conversion rate also confirmed that the nitrogen yield was also excellent. Therefore, a catalyst having a selective oxidation efficiency of ammonia has a RuO ₂ surface density of 0.6 nm ^-2 or less, and a catalyst having a RuO ₂ surface density of 0.5222 nm ^-2 is most suitable. In this case, the surface density of RuO ₂ is determined by the content of ruthenium or the specific surface area as in Equation 3 above. As the surface density of RuO ₂ increases, it can be considered that the density of RuO ₂ in a specific specific surface area is high. It is judged that if the RuO ₂ is concentrated in a narrow specific surface area, the degree of dispersion may decrease due to agglomeration. For reference, the degree of dispersion of the active metal in the noble metal catalyst can greatly affect the ammonia conversion rate and nitrogen yield.

Example 3

Ruthenium / vanadium / titania (manufacturing example 9), ruthenium / prepared as a method for enhancing the selective oxidation efficiency of ammonia according to the physical properties conditions of the titania carrier and the ruthenium / titania catalyst selected in Examples 1 and 2 Selective oxidation properties of ammonia were evaluated for tungsten / titania (Preparation 10), ruthenium / phosphorus / titania (Preparation 11) and ruthenium / yttrium / titania (Preparation 12), and the results are shown in Table 4 below. . Experimental conditions and measurement methods are the same as in Example 1, and the results of the catalyst prepared according to Preparation Example 1 are shown together for comparison.

division 200 ℃ 250 ℃ Ammonia conversion rate (%) Nitrogen yield
(%) Ammonia conversion rate (%) Nitrogen yield
(%) Preparation Example 1 0 0 85 65.3 Preparation Example 9 0 0 65 54.7 Preparation Example 10 20 19 100 76.9 Preparation Example 11 50 49 100 77.7 Preparation Example 12 20 18.4 100 78 *week
-Measured at reaction temperature of 250 ℃ and 200 ℃.

Referring to Table 4, the physical properties capable of exhibiting excellent oxidation efficiency of ammonia by supporting a desirable ruthenium content (1 part by weight) with respect to 100 parts by weight of a titania carrier suitable for the selective oxidation reaction of ammonia by showing certain physical properties basically As a result of evaluating the selective oxidation properties of ammonia by supporting vanadium, tungsten, phosphorus, and yttrium on a catalyst having properties, in the case of a catalyst prepared by supporting 0.5 parts by weight of phosphorus (Production Example 11), ammonia was completely converted at 250 ° C. And nitrogen yield was also very high.

In addition, the catalyst prepared by supporting 2 parts by weight of tungsten and 0.2 parts by weight of yttrium with respect to 100 parts by weight of the titania carrier showed excellent ammonia conversion and nitrogen yield even at a reaction temperature of 250 ° C. . Therefore, in order to enhance the reaction activity of a ruthenium / titania catalyst showing physical properties suitable for the selective oxidation reaction of ammonia, it was shown that it is preferable to further include tungsten, yttrium, and phosphorus.

The preferred embodiments of the present invention have been described above in detail. The description of the present invention is for illustration only, and those skilled in the art to which the present invention pertains will appreciate that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention. Accordingly, the scope of the present invention is indicated by the claims, which will be described later, rather than by the detailed description, and all modifications or variations derived from the meaning, scope, and equivalent concepts of the claims are included in the scope of the present invention. Should be interpreted.

Claims (12)

Oxidation catalyst for removing ammonia, characterized in that the carrier as a main component and an oxidation catalyst for removing ammonia using ruthenium as an active metal, the ruthenium is supported in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the carrier.
The oxidation catalyst for removing ammonia according to claim 1, wherein the RuO ₂ surface density is controlled to be 0.6 nm ⁻² or less.
The method according to claim 1 or 2, wherein the carrier further comprises any one metal selected from 2 parts by weight of vanadium, 2 parts by weight of tungsten, 0.5 parts by weight of phosphorus, or 0.2 parts by weight of yttrium based on 100 parts by weight of titania. Metal is an oxidation catalyst for removing ammonia, characterized in that previously supported on the titania before the ruthenium is supported.
A method for preparing an oxidation catalyst for removing ammonia, characterized in that it is prepared by supporting a ruthenium precursor so that it is 1 to 5 parts by weight of ruthenium with respect to 100 parts by weight of a carrier having titania as a main component and firing at 300 to 700 ° C.
According to claim 4, The ruthenium precursor is ruthenium nitrosyl nitrate (Ru (NO) (NO ₃ ) ₃ ), ruthenium chloride (RuCl ₃ ), ruthenium acetylacetonate (Ru (acac) ₃ ), ruthenium chloride hydrate (RuCl3 xH ₂ O) method for producing an oxidation catalyst for removing ammonia, characterized in that at least one selected from the group consisting of.
The method of claim 4, wherein the carrier is supported by firing after the oxide precursor for any one metal selected from 2 parts by weight of vanadium, 2 parts by weight of tungsten, 0.5 parts by weight of phosphorus or 0.2 parts by weight of yttrium based on 100 parts by weight of titania. Characterized in that it further comprises a process for producing an oxidation catalyst for removing ammonia.
The method of claim 6, wherein the oxide precursor supported on the titania is calcined at 400 to 600 ° C.
The method of claim 6, wherein the oxide precursor for vanadium is ammonium-methvanadate (NH ₄ VO ₃ ) or vanadium oxide (V ₂ O ₅ ), a method for preparing an oxidation catalyst for removing ammonia.
The oxidation precursor for ammonia removal according to claim 6, wherein the oxide precursor for tungsten is ammonium-tungstate ((NH ₄ ) ₁₀ H ₂ (W ₂ O ₇ ) ₆ ) or tungsten oxide (WO ₃ ). Catalyst manufacturing method.
According to claim 6, The oxide precursor for phosphorus is characterized in that the ammonium-dihydrogen phosphate (H ₆ NO ₄ P) or phosphoric acid (H ₃ PO ₄ ), the oxidation catalyst production method for removing ammonia.
7. The method of claim 6, wherein the yttrium oxide precursor is yttrium-nitrate hexahydrate (Y (NO ₃ ) ₃ 6H ₂ O).
According to any one of claims 4 to 6, wherein the oxidation catalyst is a particle, monolithic (monolith), slate and pellets prepared for the oxidation catalyst for removing ammonia, characterized in that processed in any one form selected from the group consisting of Way.

Images