KR102255628B1 - Denox catalyst improved in performance by so2 treatment and method for producing the same, denox system improved in performance by so2 treatment - Google Patents

Abstract

An object of the present invention is to provide a deNOx catalyst having improved nitrogen oxide reduction performance at medium and high temperatures by _{SO 2 treatment and a method for producing the same.} In addition, the present invention is to reduce nitrogen oxides and at the same time reduce carbon monoxide in exhaust gas generated from an internal combustion engine.
_{The deNOx catalyst having improved performance by the SO 2} treatment according to the present invention is characterized in that it is calcined in humid air by supporting ruthenium and iridium on a support, and _{then passing the SO 2 gas.}

Description

DeNOx catalyst with improved performance by SO2 treatment and its manufacturing method, deNOx system with improved performance by SO2 treatment {DENOX CATALYST IMPROVED IN PERFORMANCE BY SO2 TREATMENT AND METHOD FOR PRODUCING THE SAME, DENOX SYSTEM IMPROVED IN PERFORMANCE BY SO2 TREATMENT}

The present invention relates to a _{deNOx catalyst with improved performance by SO 2} treatment and a method for producing the same, and _{to a deNOx system with improved performance by SO 2} treatment, and more particularly, excellent in reducing nitrogen oxides at medium and high temperatures, and _{The present invention relates to a deNOx catalyst with improved performance by SO 2} treatment capable of simultaneously reducing carbon monoxide, a method for producing the same, and a deNOx system with improved performance by _{SO 2 treatment.}

Nitrogen oxides (NOx) and sulfur oxides (SOx) are representative air pollutants known to be the main causes of acid rain, respiratory diseases and photochemical smog. It is a substance. Sulfur oxides and nitrogen oxides are largely discharged from exhaust gas after combustion, and are generated in various fields such as automobiles, aircraft, ships, thermal power plants, chemical industries, and large-scale industrial facilities.

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

Nitrogen oxide (NOx) is an environmental pollutant produced by the reaction of nitrogen and oxygen. When fossil fuels such as petroleum, coal, and natural gas or other biomass are combusted, nitrogen in the atmosphere is oxygenated at high temperatures. It is produced by reacting with or by combustion with nitrogen components present in the molecules of fossil fuels. In this combustion reaction, the initial product is either in the form of nitrogen monoxide (NO) or in the form of nitrogen dioxide (NO ₂ ), and these nitrogen oxides are collectively referred to as NOx. In particular, among these NOx, NO accounts for 90 to 95% of the total nitrogen oxide emissions, and it is known that the emissions slightly change depending on the combustion fuel or combustion conditions.

These nitrogen oxides are compounds with unpaired electrons, which combine with water vapor (or moisture) in the atmosphere to induce acid rain, and have the property of absorbing solar radiation energy, which causes global warming. In addition, when nitrogen monoxide produced by combustion is released into the atmosphere, it is oxidized to nitrogen dioxide, which is harmful to the human body. The generated nitrogen dioxide is well known as a representative air pollutant and pollutant that generates ozone, a secondary pollutant, through a photochemical reaction when released into the atmosphere, and when released into the atmosphere. Therefore, from the viewpoint of air pollution and global warming, it is a very important issue to prepare a plan to reduce nitrogen oxides emitted into the atmosphere.

Meanwhile, most ships operating at sea have used diesel generators in consideration of fuel cost reduction and operation cost. However, these devices also contain nitrogen oxides (NOx), sulfur oxides (SOx), and carbon dioxide (CO ₂ ), which are major air pollutants, in the exhaust gas emitted after combustion, like other internal combustion engines. It accounts for about 4~9%, 10~15%, and 2~3% of the total amount.

Accordingly, the International Marine Organization (IMO), an international maritime organization, is reinforcing environmental regulations on nitrogen oxides and sulfur oxides in accordance with Marpol Annex VI regulations in order to regulate ship emissions. In order to cope with such regulations, recently, a post-treatment device such as an exhaust gas recirculation device, a desulfurization device, and a selective catalytic reducing agent is applied, or a dual fuel generator using natural gas, which is an eco-friendly fuel, is used.

Selective catalytic reduction (SCR), one of the methods of removing nitrogen oxides, reacts NOx with a reducing agent while simultaneously passing exhaust gas and a reducing agent through the catalyst, and reducing it with nitrogen and water vapor. The conventional SCR system has a disadvantage in that the overall size of the SCR system is increased due to the urea supply device, and the application of the conventional SCR system including a general dust collector to a relatively narrow ship reduces the space used for the ship. In addition, the SCR system must be designed in consideration of the conditions of the ship, and the dust collector may cause difficulty in the overall design of the SCR system.

Conventional ship SCR systems _{used urea or NH 3} as a reducing agent, and since such urea must be supplied to the selective reduction catalyst in a liquid state, an auxiliary system was required for the storage container and the injection device. In addition, since the existing liquid urea system injects a liquid and vaporizes urea by heat from the exhaust gas, there is a problem that urea is not vaporized but is produced as solid ammonium when the exhaust gas temperature is injected under conditions of 200 ℃ or lower. come.

In addition, conventional catalysts for reducing nitrogen oxides have a problem in that their ability to reduce nitrogen oxides is deteriorated at medium and high temperatures of 175°C or higher. Accordingly, the present inventors completed the present invention to find a way to effectively reduce nitrogen oxides at medium and high temperatures.

Korean Patent Registration No. 10-1798713 (2017.01.25.)

An object of the present invention is to provide a deNOx catalyst having improved nitrogen oxide reduction performance at medium and high temperatures and a method for producing the same.

Another object of the present invention is to reduce nitrogen oxides and at the same time reduce carbon monoxide (CO) in exhaust gas generated from an internal combustion engine.

Another object of the present invention is to reduce nitrogen oxides without introducing a separate reducing agent by using carbon monoxide (CO) present in exhaust gas as a reducing agent.

In order to achieve the above object, the present invention is a catalyst for reducing nitrogen oxides (NOx) using carbon monoxide (CO) in exhaust gas as a reducing agent, supporting ruthenium and iridium on a support and calcined under humid air, and then SO ₂ gas It provides a deNOx catalyst with improved performance by _{SO 2} treatment, characterized in that passing through.

The iridium may be supported in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support.

The ruthenium may be supported in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support.

The sintering may be performed for 1 to 10 hours at a temperature of 300 to 800 °C in moist air.

The SO ₂ gas may be passed at a concentration of 0.001 to 10 vol.%.

The support may be any one selected from the group consisting of aluminum oxide, zirconia, titania, silica, zeolite, ceria, and ceria-based multi-component compounds.

In addition, the present invention to achieve the above object (a) the steps of preparing a mixture of ruthenium and iridium; (b) supporting the ruthenium and iridium mixture on a support; (c) firing the support on which the ruthenium and iridium of the step (b) are supported; Provides a process for the preparation of a deNOx catalyst is enhanced by the SO ₂ treatment including a; and (d) passing the SO ₂ gas in the fired support of step (c).

The support in step (c) may be any one selected from the group consisting of aluminum oxide, zirconia, titania, silica, zeolite, ceria, and ceria-based multi-component compounds.

The sintering of step (c) may be performed for 1 to 10 hours at a temperature of 300 to 800 °C in moist air.

In the step (d), the SO ₂ gas may be passed at a concentration of 0.001 to 10 vol.%.

In addition, the present invention to achieve the above object (e) the step of injecting the exhaust gas into the housing; _{(f) reducing nitrogen oxides (NOx) to N 2} by injecting carbon monoxide (CO) into the housing for reduction of nitrogen oxides (NOx); (g) contacting the exhaust gas with an iridium and ruthenium complex catalyst; And (h) _{passing SO 2} gas through the complex catalyst to improve nitrogen oxide reduction performance; and SO ₂ treatment provides a deNOx system with improved performance.

In the step (h), the SO ₂ gas may be passed at a concentration of 0.001 to 10 vol.%.

_{Using the deNOx catalyst having improved performance by SO 2} treatment according to the present invention and a method for producing the same, it is possible to solve the problem that the activity of the catalyst for reducing nitrogen oxides decreases at medium and high temperatures of 175°C or higher.

In addition, if the _{deNOx system with improved performance by the SO 2 treatment according to the present invention is used, the nitrogen oxide reduction performance can be improved through SO 2} and CO contained in the exhaust gas, and the device can use carbon monoxide in the exhaust gas. It is simple and has an economic advantage.

1 is a process flow chart showing a method of manufacturing a deNOx catalyst with improved performance by treatment with _{SO 2} according to the present invention.
2 is a process flow diagram of a deNOx system with improved performance by _{SO 2} treatment according to the present invention.
_{3 shows NO, NO 2,} and NO over time when using the deNOx catalyst with improved performance by _{the SO 2} treatment according to the present invention. Of SO ₂ It is a graph showing the change in concentration.
4 is a graph comparing the nitrogen oxide removal performance of deNOx catalysts prepared according to Examples 1 and 2 and Comparative Example 1 by temperature.

In the following description, it should be noted that only parts necessary for understanding the embodiments of the present invention will be described, and descriptions of other parts will be omitted without distracting the gist of the present invention.

The terms or words used in the present specification and claims described below should not be construed as being limited to a conventional or dictionary meaning, and the inventor is appropriate as a concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention on the basis of the principle that it can be defined as such.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all the technical spirit of the present invention, and various equivalents that can replace them at the time of application It should be understood that there may be variations and variations.

Hereinafter, the present invention will be described with reference to the drawings.

SO ₂ DeNOx catalyst with improved performance by treatment

_{The deNOx catalyst with improved performance by the SO 2} treatment according to the present invention is a catalyst that reduces nitrogen oxides (NOx) using carbon monoxide (CO) in exhaust gas as a reducing agent, and is calcined in moist air by supporting ruthenium and iridium on a support. Afterwards, it is characterized in that the _{SO 2 gas is passed.}

The deNOx catalyst with improved performance by _{the SO 2} treatment according to the present invention can be used for SCR. SCR is a technology for removing nitrogen oxides in exhaust gas generated during operation of onshore plants, ships and automobiles with selective catalytic reduction. That is, SCR is used to reduce nitrogen oxides in exhaust gas generated from ship engines or boilers, or from boilers or incinerators of onshore plants. SCR is one of the nitrogen oxide reduction systems using the selective catalytic reduction method, and is configured to react with the nitrogen oxide and the reducing agent while simultaneously passing the exhaust gas and the reducing agent through the catalyst to reduce it to nitrogen and water vapor.

_{In general, SCR uses ammonia (NH 3} ) or urea to provide ammonia as a reducing agent for reducing nitrogen oxides, and uses a catalyst having an active temperature range of 200°C to 400°C.

_{However, the deNOx catalyst with improved performance by SO 2} treatment according to an embodiment of the present invention uses carbon monoxide (CO) in exhaust gas as a reducing agent to remove nitrogen oxides. Since the exhaust gas of the internal combustion engine may contain hydrocarbons, carbon monoxide, carbon dioxide, hydrogen, nitrogen, oxygen, sulfur oxides, and water in addition to nitrogen oxides, nitrogen oxides can be removed by using carbon monoxide in the exhaust gas as a reducing agent.

When carbon monoxide in the exhaust gas is used as a reducing agent, there is no need for an auxiliary system such as a container for storing urea and an injection device in the related art, so that the space in the internal combustion engine can be utilized, and there is no additional cost, which is economical. In addition, there is an advantage of reducing nitrogen oxides and simultaneously removing carbon monoxide in exhaust gas.

Examples of nitrogen oxides removed according to the present invention include nitrogen monoxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetraoxide, dinitrogen monoxide, and mixtures thereof. Preferably, they are nitrogen monoxide, nitrogen dioxide, and dinitrogen monoxide. The nitrogen oxide concentration in the exhaust gas that can be treated by the present invention is not limited.

_{The deNOx catalyst having improved performance by the SO 2} treatment according to an embodiment of the present invention may be prepared by supporting ruthenium and iridium on a support, sintering in moist air, and _{passing SO 2} gas.

Iridium is an element with an atomic number of 77 and an element symbol of Ir, a transition metal. Iridium is hard, but has little ductility and is difficult to process because it breaks easily. The lump is silvery white, but the powder is black.

The amount of iridium supported is preferably in an appropriate range, but may be supported in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support in order to sufficiently achieve the purpose of increasing the nitrogen oxide removal efficiency.

If iridium is supported in an amount of less than 0.1 parts by weight, the activity of the catalyst is not secured, and if it is supported in an amount exceeding 10 parts by weight, the degree of improvement in the activity of the catalyst is insignificant and economically unfavorable, so the above range is preferable.

The iridium compound useful for preparing the deNOx catalyst according to an embodiment of the present invention may be any compound that can be easily converted into a water-soluble or partially water-soluble compound, and can be deposited on a support. For example, iridium in a metallic state, an iridium salt, an oxide, etc. are preferable, but are not limited thereto.

As the iridium salt, iridium halide is generally used. More specifically, the iridium halide may be IrI ₃ , IrBr ₃ , IrCl ₃ , IrI ₃ ·4H ₂ O and IrBr ₃ ·4H ₂ O, and it is preferable to use _{IrCl 3.}

Ruthenium is an element with atomic number 44 and is a transition metal located in the center of the periodic table and is one of the platinum group metals.

The amount of ruthenium may be supported in an appropriate range, but in order to sufficiently exhibit the purpose of increasing the removal efficiency of nitrogen oxides at medium and high temperatures, it is preferably supported in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support.

0.1 part by weight of the ruthenium supported amount is an optimal amount for securing the activity of the catalyst, and even if the amount exceeded 10 parts by weight, the improvement of the activity of the catalyst is insignificant and economically unfavorable, so the above range is preferable.

The ruthenium compound useful for preparing the deNOx catalyst according to an embodiment of the present invention may be any compound that can be easily converted into a water-soluble or partially water-soluble compound, and can be deposited on a support.

Examples of the ruthenium compound include RuCl ₃ and Ru(NO)(NO ₃ ) ₃ , but are not limited thereto, and it is preferable to use _{RuCl 3.}

The deNOx catalyst according to an embodiment of the present invention may additionally support other noble metals in addition to ruthenium and iridium.

The noble metal component that may be additionally supported may be at least one selected from the group consisting of platinum, rhodium, palladium, and silver. Among the noble metals, platinum, rhodium, and silver are preferred.

In this case, platinum is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the support, and rhodium and silver are also preferably 0.1 to 10 parts by weight, respectively, based on 100 parts by weight of the support.

If the supported amount is less than 0.1 parts by weight, the effect of supporting additional precious metals is not exhibited, and when the amount exceeds 10 parts by weight, the properties of ruthenium and iridium, which are the main components, may be deteriorated, so the above range is preferable. In addition, the additional noble metal may additionally support two or more noble metals of platinum, rhodium, and silver with respect to iridium and ruthenium.

In the deNOx catalyst according to an embodiment of the present invention, ruthenium may be primarily supported on a support and then iridium may be secondarily supported. In addition, it is preferable that the deNOx catalyst according to an embodiment of the present invention simultaneously supports ruthenium and iridium in order to prevent iridium from being supported earlier than ruthenium.

This is because when iridium is first supported on the support and then ruthenium is supported, iridium and ruthenium exist separately due to the strong interaction between iridium and the support, so that a synergy effect between iridium and ruthenium cannot be expected.

Therefore, when ruthenium is first supported on the support and then iridium is supported, a strong interaction between the support and iridium can be prevented, and iridium and ruthenium are present close to each other, thereby improving performance.

The deNOx catalyst according to an embodiment of the present invention may use one selected from the group consisting of aluminum oxide, zirconia, titania, silica, zeolite, ceria, and ceria-based multi-component compounds as a support. At this time, it is preferable to use aluminum oxide as a support, and the aluminum oxide may be monolithized and supported in a mixture solution of iridium and ruthenium to form a catalyst layer.

In addition, the support may sequentially include a ruthenium layer and an iridium layer on a monolith, the ruthenium layer may be supported on the outer surface and inner pores of the support, and may be formed by stacking an iridium layer on the ruthenium layer. have.

The aluminum oxide is generally called alumina, and is a colorless or white material that is insoluble in water. α alumina is a product of the Bayer method and has a melting point of 199 to 202 °C, and β alumina is in a stable form at high temperatures (1,500 °C). γ alumina is obtained by heating and dehydrating a hydrate or α hydrated alumina and further maintaining it at 900°C, and has a property of transitioning to α alumina when the temperature is 1,000°C or higher.

The aluminum oxide is preferred for use as a support for a catalyst because of its high specific surface area and good heat resistance against firing at elevated temperatures.

It is preferable to use the aluminum oxide having a specific surface area of 5 or more, specifically 50 or more, and more specifically 100 m ^{2 /g or more.} When the specific surface area of the aluminum oxide is less than 5, there is a disadvantage that the activity of the catalyst is deteriorated, and the above range is preferable.

The deNOx catalyst according to an embodiment of the present invention may be calcined for 1 to 10 hours at a temperature of 300 to 800° C. in moist air.

Firing at a temperature within the above range can increase the removal efficiency of nitrogen oxides at a temperature of 175° C. or higher. In addition, when firing exceeding 800° C., the catalyst component may be volatilized, and the active point of the catalyst may decrease due to sintering, thereby reducing the performance of the catalyst. In addition, the above-described range is preferable because a problem of high energy consumption due to high temperature may occur.

The sintering may be carried out under hydrogen, argon, and positive air pressure, but it is preferably carried out under humid air.

When firing is performed in a hydrogen atmosphere, the catalyst structure is different, and it is not easy to remove the constituents of the iridium and ruthenium mixture, so it is preferable to perform the firing in humid air.

DeNOx system according to an embodiment of the present invention is injected into the SO ₂ gas from the outside of the iridium and ruthenium complex catalyst, or to take advantage of a SO ₂ component contained in the exhaust gas. However, to take advantage of a SO ₂ component contained in the exhaust gas It is desirable.

Conventional iridium and ruthenium complex catalysts maintain activity only at low temperatures, and there is a problem in that activity is inferior at medium and high temperatures.

However, in the case of passing the exhaust gas through the iridium and ruthenium complex catalyst and passing the SO ₂ gas according to an embodiment of the present invention, the nitrogen oxide reduction performance at a high temperature may be improved.

In addition, since the exhaust gas contains not only nitrogen oxides but also SO _{2 components, it is possible to utilize the SO 2} component in the exhaust gas, so that an internal combustion engine does not require an auxiliary system such as a container for storing _{SO 2 gas and an injection device.} It has an economic advantage because it can utilize the space inside and does not incur additional costs.

It is preferable to pass the SO ₂ gas at a concentration of 0.001 to 10 vol.%.

SO ₂ Method for producing deNOx catalyst with improved performance by treatment

According to another aspect of the present invention, the present invention comprises the steps of: (a) preparing a mixture of ruthenium and iridium; (b) supporting the ruthenium and iridium mixture on a support; (c) firing the support on which the ruthenium and iridium of the step (b) are supported; Provides a process for the preparation of a deNOx catalyst is enhanced by the SO ₂ treatment including a; and (d) passing the SO ₂ gas in the fired support of step (c).

1 is a process flow chart showing a method of manufacturing a deNOx catalyst with improved performance by treatment with _{SO 2} according to the present invention.

_{Hereinafter, a method of manufacturing a deNOx catalyst having improved performance by treatment with SO 2} according to an embodiment of the present invention will be described in detail step by step with reference to FIG. 1.

First, a mixture of ruthenium and iridium is prepared (S10).

In order to support the ruthenium and iridium metal on the support, a solution containing the ruthenium and iridium metal compound is prepared.

As the solvent, an aqueous solvent containing water or water as a main component, or various organic solvents such as alcohol and ether may be used, but since the solubility of the ruthenium and iridium metal compounds is large, it is preferable to use water or an aqueous solvent containing water as the main component. desirable.

For preparing the ruthenium and iridium mixture, the iridium compound may be any compound that can be water-soluble or partially converted into a water-soluble compound, and can be deposited on a support. For example, iridium in a metallic state, an iridium salt, an oxide, etc. are preferable, but are not limited thereto.

As the iridium salt, iridium halide is generally used. More specifically, the iridium halide may be IrI ₃ , IrBr ₃ , IrCl ₃ , IrI ₃ ·4H ₂ O and IrBr ₃ ·4H ₂ O, and it is preferable to use _{IrCl 3.}

For preparing the ruthenium and iridium mixture, the ruthenium compound may be any compound that can be water-soluble or partially converted into a water-soluble compound and can be deposited on a support.

Examples of the ruthenium compound include RuCl ₃ and Ru(NO)(NO ₃ ) ₃ , but are not limited thereto, and it is preferable to use _{RuCl 3.}

Next, a mixture of ruthenium and iridium is supported on the support (S20).

As the support, any one selected from the group consisting of aluminum oxide, zirconia, titania, silica, zeolite, ceria and ceria series multi-component compounds may be used.

Ruthenium may be primarily supported on the support, and then iridium may be secondarily supported on the support. In addition, it is preferable that the deNOx catalyst according to an embodiment of the present invention simultaneously supports ruthenium and iridium in order to prevent iridium from being supported earlier than ruthenium.

The reason why the ruthenium and iridium mixture are simultaneously supported on the support is to prevent iridium from being first supported on the support. That is, if iridium is first supported on the support, a synergistic effect of iridium and ruthenium cannot be expected due to a strong interaction between iridium and the support. In addition, when the ruthenium and iridium are supported on the support, the effect of improving the nitrogen oxide removal performance at 175° C. or higher can be expected only when the ruthenium and iridium are present in close proximity.

Next, the support on which ruthenium and iridium are supported is fired (S30).

The firing step may be performed for 1 to 10 hours at a temperature of 300 to 800 °C in humid air.

Firing at a temperature within the above range can increase the removal efficiency of nitrogen oxides at a temperature of 175° C. or higher. In addition, when firing exceeding 800° C., the catalyst component may be volatilized, and the active point of the catalyst may decrease due to sintering, thereby reducing the performance of the catalyst. In addition, the above-described range is preferable because a problem of high energy consumption due to high temperature may occur.

The sintering may be carried out under hydrogen, argon, and positive air pressure, but it is preferably carried out under humid air.

When firing is performed in a hydrogen atmosphere, the catalyst structure is different, and it is not easy to remove the constituents of the iridium and ruthenium mixture, so it is preferable to perform the firing in humid air.

Finally, the fired support _{is passed through the SO 2} gas (S40).

DeNOx system according to an embodiment of the present invention is injected into the SO ₂ gas from the outside of the iridium and ruthenium complex catalyst, or to take advantage of a SO ₂ component contained in the exhaust gas. However, to take advantage of a SO ₂ component contained in the exhaust gas It is desirable.

Conventional iridium and ruthenium complex catalysts maintain activity only at low temperatures, and there is a problem in that activity is inferior at medium and high temperatures.

However, in the case of passing the exhaust gas through the iridium and ruthenium complex catalyst and passing the SO ₂ gas according to an embodiment of the present invention, the nitrogen oxide reduction performance at a high temperature may be improved.

In addition, since the exhaust gas contains not only nitrogen oxides but also SO _{2 components, it is possible to utilize the SO 2} component in the exhaust gas, so that an internal combustion engine does not require an auxiliary system such as a container for storing _{SO 2 gas and an injection device.} It has an economic advantage because it can utilize the space inside and does not require additional cost.

SO ₂ DeNOx system with improved performance by processing

According to another aspect of the present invention, the present invention comprises the steps of: (e) injecting exhaust gas into the housing; _{(f) reducing nitrogen oxides (NOx) to N 2} by injecting carbon monoxide (CO) into the housing for reduction of nitrogen oxides (NOx); (g) contacting the exhaust gas with an iridium and ruthenium complex catalyst; And (h) the performance by the SO ₂ treatment, which was passed through the SO ₂ gas to the catalytic composite comprising the step of improving the NOx reduction performance provides improved deNOx system.

2 is a flow chart of a process flow diagram of a deNOx system with improved performance by _{SO 2} treatment according to the present invention, _{and FIG. 3 is a NO, NO 2 over} time when using a deNOx catalyst with improved performance by _{SO 2} treatment according to the present invention, And a graph showing the change in the concentration of _{SO 2.}

Hereinafter, a deNOx system with improved performance by _{SO 2} processing according to the present invention will be described in detail with reference to FIGS. 2 to 3.

First, exhaust gas is injected into the housing (S100).

The housing may have an inlet and an outlet so that exhaust gas is introduced and discharged. Exhaust gas generated by combustion of the engine is introduced through the inlet of the housing, and nitrogen oxide contained in the exhaust gas is reduced to _{N 2 and discharged through the outlet of the housing.}

The exhaust gas is generated by engine combustion of an internal combustion engine. The internal combustion engine may be an automobile, a ship, an industrial machine, a power plant, an incinerator, or a boiler.

The exhaust gas may include nitrogen oxide, hydrocarbon, carbon dioxide, carbon monoxide, hydrogen, nitrogen, oxygen, sulfur oxide, particulate matter, and water.

Nitrogen oxides in the exhaust gas introduced through the inlet are reduced inside the housing and are reduced to nitrogen (N ₂ ), carbon dioxide (CO ₂ ), and water (H ₂ O). At this time, the reduced nitrogen and carbon dioxide are discharged through the outlet of the housing.

Examples of nitrogen oxides removed according to the present invention include nitrogen monoxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetraoxide, dinitrogen monoxide, and mixtures thereof. Preferably, they are nitrogen monoxide, nitrogen dioxide, and dinitrogen monoxide. The nitrogen oxide concentration of the exhaust gas that can be treated by the present invention is not limited.

Next, carbon monoxide is injected into the housing to reduce nitrogen oxides (S200).

In the deNOx system according to an embodiment of the present invention, carbon monoxide may be injected from the outside for reduction of nitrogen oxide or carbon monoxide contained in the exhaust gas may be used, but it is preferable to use carbon monoxide contained in the exhaust gas as a reducing agent.

The exhaust gas of the internal combustion engine may include hydrocarbons, carbon monoxide, carbon dioxide, hydrogen, nitrogen, oxygen, sulfur oxides, and water in addition to nitrogen oxides. Therefore, when carbon monoxide in the exhaust gas is used as a reducing agent, there is no need for an auxiliary system such as a container for storing urea and an injection device in the related art, so that the space in the internal combustion engine can be utilized, and there is no additional cost, so there is an economic advantage. In addition, there is an advantage in that carbon monoxide in exhaust gas can be removed at the same time as reducing nitrogen oxides.

Next, the exhaust gas is brought into contact with the iridium and ruthenium complex catalyst (S300).

The iridium and ruthenium composite catalyst may be prepared by supporting ruthenium and iridium on a support, sintering in moist air, and _{passing SO 2} gas.

Iridium is an element with an atomic number of 77 and an element symbol of Ir, a transition metal. Iridium is hard, but has little ductility and is difficult to process because it breaks easily. The lump is silvery white, but the powder is black.

The amount of iridium supported is preferably in an appropriate range, but may be supported in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support in order to sufficiently achieve the purpose of increasing the nitrogen oxide removal efficiency.

If iridium is supported in an amount of less than 0.1 parts by weight, the activity of the catalyst is not secured, and if it is supported in an amount exceeding 10 parts by weight, the degree of improvement in the activity of the catalyst is insignificant and economically unfavorable, so the above range is preferable.

The iridium compound useful for preparing the deNOx catalyst according to an embodiment of the present invention may be any compound that can be easily converted into a water-soluble or partially water-soluble compound, and can be deposited on a support. For example, iridium in a metallic state, an iridium salt, an oxide, etc. are preferable, but are not limited thereto.

As the iridium salt, iridium halide is generally used. More specifically, the iridium halide may be IrI ₃ , IrBr ₃ , IrCl ₃ , IrI ₃ ·4H ₂ O and IrBr ₃ ·4H ₂ O, and it is preferable to use _{IrCl 3.}

Ruthenium is an element with atomic number 44 and is a transition metal located in the center of the periodic table and is one of the platinum group metals.

The amount of ruthenium may be supported in an appropriate range, but in order to sufficiently exhibit the purpose of increasing the removal efficiency of nitrogen oxides at medium and high temperatures, it is preferably supported in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support.

0.1 part by weight of the ruthenium supported amount is an optimal amount for securing the activity of the catalyst, and even if the amount exceeded 10 parts by weight, the improvement of the activity of the catalyst is insignificant and economically unfavorable, so the above range is preferable.

The ruthenium compound useful for preparing the deNOx catalyst according to an embodiment of the present invention may be any compound that can be easily converted into a water-soluble or partially water-soluble compound, and can be deposited on a support.

Examples of the ruthenium compound include RuCl ₃ and Ru(NO)(NO ₃ ) ₃ , but are not limited thereto, and it is preferable to use _{RuCl 3.}

The deNOx catalyst according to an embodiment of the present invention may additionally support other noble metals in addition to ruthenium and iridium.

The deNOx catalyst according to an embodiment of the present invention may additionally support other noble metals in addition to ruthenium and iridium.

The noble metal component that may be additionally supported may be at least one selected from the group consisting of platinum, rhodium, palladium, and silver. Among the noble metals, platinum, rhodium, and silver are preferred.

In this case, platinum is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the support, and rhodium and silver are also preferably 0.1 to 10 parts by weight, respectively, based on 100 parts by weight of the support.

If the supported amount is less than 0.1 parts by weight, the effect of supporting additional noble metals is not exhibited, and when the amount exceeds 10 parts by weight, the properties of ruthenium and iridium, which are main components, may be deteriorated, so the above range is preferable. In addition, the additional noble metal may additionally support two or more noble metals of platinum, rhodium, and silver with respect to iridium and ruthenium.

In the deNOx catalyst according to an embodiment of the present invention, ruthenium may be primarily supported on a support and then iridium may be secondarily supported. In addition, the deNOx catalyst according to an embodiment of the present invention may simultaneously support ruthenium and iridium in order to prevent iridium from being supported earlier than ruthenium.

This is because when iridium is first supported on the support and then ruthenium is supported, iridium and ruthenium exist separately due to the strong interaction between iridium and the support, so that a synergy effect between iridium and ruthenium cannot be expected.

Therefore, when ruthenium is first supported on the support and then iridium is supported, a strong interaction between the support and iridium can be prevented, and iridium and ruthenium are present close to each other, thereby improving performance.

The deNOx catalyst according to an embodiment of the present invention may use one selected from the group consisting of aluminum oxide, zirconia, titania, silica, zeolite, ceria, and ceria-based multi-component compounds as a support. At this time, it is preferable to use aluminum oxide as a support, and the aluminum oxide may be monolithized and supported in a mixture solution of iridium and ruthenium to form a catalyst layer.

In addition, the support may sequentially include a ruthenium layer and an iridium layer on a monolith, the ruthenium layer may be supported on the outer surface and inner pores of the support, and may be formed by stacking an iridium layer on the ruthenium layer. have.

The aluminum oxide is generally called alumina, and is a colorless or white material that is insoluble in water. α alumina is a product of the Bayer method and has a melting point of 199 to 202 °C, and β alumina is in a stable form at high temperatures (1,500 °C). γ alumina is obtained by heating and dehydrating a hydrate or α hydrated alumina and further maintaining it at 900°C, and has a property of transitioning to α alumina when the temperature is 1,000°C.

The aluminum oxide is preferred for use as a support for a catalyst because of its high specific surface area and good heat resistance against firing at elevated temperatures.

It is preferable to use the aluminum oxide having a specific surface area of 5 or more, specifically 50 or more, and more specifically 100 m ^{2 /g or more.} When the specific surface area of the aluminum oxide is less than 5, there is a disadvantage that the activity of the catalyst is deteriorated, and the above range is preferable.

The deNOx catalyst according to an embodiment of the present invention may be calcined for 1 to 10 hours at a temperature of 300 to 800° C. in moist air.

Firing at a temperature within the above range can increase the removal efficiency of nitrogen oxides at a temperature of 175°C or higher. In addition, when firing exceeding 800° C., the catalyst component may be volatilized, and the active point of the catalyst may decrease due to sintering, thereby reducing the performance of the catalyst. In addition, the above-described range is preferable because there may be a problem that energy consumption is large due to high temperature.

The sintering may be carried out under hydrogen, argon, and positive air pressure, but it is preferably carried out under humid air.

When firing is performed in a hydrogen atmosphere, the catalyst structure is different, and it is not easy to remove the constituents of the iridium and ruthenium mixture, so it is preferable to perform the firing in humid air.

_{Finally, the SO 2} gas is passed through the iridium and ruthenium complex catalyst (S400).

DeNOx system according to an embodiment of the present invention is injected into the SO ₂ gas from the outside of the iridium and ruthenium complex catalyst, or to take advantage of a SO ₂ component contained in the exhaust gas. However, to take advantage of a SO ₂ component contained in the exhaust gas It is desirable.

The SO ₂ gas may be passed at a concentration of 0.001 to 10 vol.%.

Conventional iridium and ruthenium complex catalysts maintain activity only at low temperatures, and there is a problem in that activity is inferior at medium and high temperatures. However, according to an embodiment of the present invention, when the exhaust gas is passed through the iridium and ruthenium complex catalyst and the SO ₂ gas is passed, the nitrogen oxide reduction performance of the catalyst is improved.

Referring to Figure 3, SO ₂ in the period in which the concentration of SO ₂ gas increases as the gas injection was able to confirm that reducing the concentration of NO and NO _2, was passed through the SO ₂ gas to the catalyst, the concentration of SO ₂ When is again decreased, it was confirmed that the concentration _{of NO and NO 2 increased.} As described above, it was confirmed that the nitrogen oxide reduction performance was improved when the _{SO 2} gas was passed through the catalyst according to the present invention.

According to this, since the exhaust gas contains not only nitrogen oxides but also SO _{2 components, it is possible to utilize the SO 2} component in the exhaust gas, thereby eliminating the need for ancillary systems such as a container for storing _{SO 2 gas and an injection device.} It is possible to utilize the space in the institution and has an economic advantage as there is no additional cost.

Example

Hereinafter, the present invention will be described in more detail by examples and experimental examples. However, the following Examples and Experimental Examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Comparative Example 1: IrRu/Al ₂ O ₃ Preparation of catalyst

First, 0.190 g of _{IrCl 3 sample and 0.193 g of RuCl 3} sample were simultaneously dissolved in water, and then immersed in 5 g of γ-aluminum oxide, and then dried at 100° C. for 12 hours. After drying, the sample was calcined for 4 hours at a temperature of 500° C. in humid air, and an IrRu/Al ₂ O ₃ catalyst in which iridium-ruthenium was supported on aluminum oxide was prepared.

Example 1: IrRu/Al ₂ O ₃ 20 ppm SO in the catalyst ₂ Gas treatment

In the IrRu/Al ₂ O ₃ catalyst prepared in Comparative Example 1 20 ppm of SO ₂ gas was passed.

Example 2: IrRu/Al ₂ O ₃ 100 ppm SO in the catalyst ₂ Gas treatment

In the IrRu/Al ₂ O ₃ catalyst prepared in Comparative Example 1, 100 ppm of SO ₂ gas was passed.

Experimental Example 1: Confirmation of nitrogen oxide removal performance

The catalysts prepared in Examples 1 and 2 and Comparative Example 1 were measured for nitrogen oxide removal performance under the following conditions.

Nitrogen oxide (NO): 50 ppm

CO: 0.7%

O2: 5% and N ₂ balanced and GHSV ^{was measured under the conditions of 200,000 h -1} and the experimental results are shown in FIG. 5.

<Evaluation>

4 is a graph comparing the nitrogen oxide removal performance of Examples 1 and 2 and Comparative Example 1 by temperature.

As a result, as shown in FIG. 4, the catalyst prepared by Comparative Example 1 increases the nitrogen oxide conversion rate while the temperature increases from 150° C. to 175° C., and the nitrogen oxide conversion rate reaches 90% at 175° C. However, when the temperature was higher than 175 ℃, it was confirmed that the conversion ratio of nitrogen oxides gradually decreased, and the conversion ratio was as low as 30% from the temperature higher than 250 ℃.

However, it was confirmed that the catalysts prepared according to Examples 1 and 2 maintained a high nitrogen oxide conversion rate even at a temperature of 175°C or higher and exhibited a conversion rate of 50% or more even at 300°C.

Accordingly, it can be seen that the nitrogen oxide reduction performance at a high temperature is improved when the exhaust gas is passed through the iridium and ruthenium composite catalyst and the SO _{2 gas is passed through according to an embodiment of the present invention.}

Since the exhaust gas contains not only nitrogen oxides but also SO ₂ components, it is possible _{to utilize the SO 2} component in the exhaust gas, so there is no need for an auxiliary system such as a container for storing _{SO 2 gas and an injection device.} It can be used and has an economic advantage as there is no additional cost.

_{So far, specific examples of a deNOx catalyst having improved performance by SO 2} treatment according to an embodiment of the present invention, a method for producing the same, and a _{deNOx system having improved performance by SO 2} treatment have been described, but within the scope of the present invention It is obvious that various implementation modifications are possible within the limit that does not deviate.

Therefore, the scope of the present invention should not be defined by being limited to the described embodiments, and should be defined by the claims and equivalents as well as the claims to be described later.

That is, it should be understood that the above-described embodiments are illustrative in all respects and not limiting, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims and All changes or modified forms derived from the equivalent concept should be construed as being included in the scope of the present invention.

Claims (12)

As a catalyst for reducing nitrogen oxides (NOx) using carbon monoxide (CO) in exhaust gas as a reducing agent,
After supporting ruthenium and iridium on a support and firing in moist air, SO ₂ gas is passed through at a concentration of more than 0.002 and not more than 0.01 vol.%,
The support is one selected from the group consisting of aluminum oxide, zirconia, titania, zeolite, ceria and ceria series multi-component compounds,
After passing through the SO ₂ gas is also enhanced by stopping the supply of the SO ₂ gas by the SO ₂ treatment, characterized in that the deNOx performance maintained deNOx catalyst. The method of claim 1,
The iridium is
DeNOx catalyst with improved performance by _{SO 2} treatment, characterized in that supported by 0.1 to 10 parts by weight based on 100 parts by weight of the support. The method of claim 1,
The ruthenium is
DeNOx catalyst with improved performance by _{SO 2} treatment, characterized in that supported by 0.1 to 10 parts by weight based on 100 parts by weight of the support. The method of claim 1,
The firing is
DeNOx catalyst with improved performance by _{SO 2} treatment, characterized in that it is performed for 1 to 10 hours at a temperature of 300 to 800 °C in moist air. delete delete (a) preparing a mixture of ruthenium and iridium;
(b) supporting the ruthenium and iridium mixture on a support;
(c) firing the support on which the ruthenium and iridium of the step (b) are supported; And
_{(d) passing SO 2} gas at a concentration of more than 0.002 and not more than 0.01 vol.% through the calcined support of step (c); including,
_{Even if the supply of the SO 2} gas is stopped after the step (c), the deNOx performance is maintained,
(C) the support of the step is process for producing a deNOx catalyst is enhanced by the SO ₂ treatment, characterized in that one selected from the group is aluminum oxide, zirconia, titania, zeolite, ceria, and ceria series consisting of component compounds. delete The method of claim 7,
The firing of step (c) is
A method for producing a deNOx catalyst having improved performance by _{SO 2} treatment, characterized in that it is carried out for 1 to 10 hours at a temperature of 300 to 800° C. in moist air. delete (e) injecting exhaust gas into the housing;
_{(f) reducing nitrogen oxides (NOx) to N 2} by injecting carbon monoxide (CO) into the housing for reduction of nitrogen oxides (NOx);
(g) contacting the exhaust gas with an iridium and ruthenium complex catalyst; And
_{(h) improving the nitrogen oxide reduction performance by passing SO 2} gas through the complex catalyst at a concentration of more than 0.002 and not more than 0.01 vol.%; including,
_{Even if the supply of the SO 2} gas is stopped after the step (h), the deNOx performance is maintained,
The complex catalyst of step (h) is calcined under humid air by supporting ruthenium and iridium on a support,
The support is one selected from the group consisting of aluminum oxide, zirconia, titania, zeolite, ceria and ceria-based multi-component compounds. DeNOx system with improved performance by _{SO 2 treatment.}
delete

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