WO2020005026A1 - Denox catalyst having improved nox reduction performance, method for producing same, and nox reduction method - Google Patents

Abstract

The deNOx catalyst having improved NOx reduction performance, according to the present invention, is characterized in that a support, on which ruthenium and iridium are supported, is fired and is surface-modified with a gas comprising sulfur.

Description

DeNox catalyst with improved NOx reduction performance, method for producing same and NOx reduction method

The present invention relates to a deNOx catalyst having improved NOx reduction performance, a manufacturing method thereof, and a NOx reduction method, and more particularly, a NOx reduction that further improves NOx reduction performance by reforming the surface of the catalyst with a gas containing sulfur. The present invention relates to a deNOx catalyst having improved performance, a method for preparing the same, and a method for reducing NOx.

Nitrogen oxides are mainly generated from mobile sources such as automobiles, and fixed sources such as industrial and power generation facilities, and have a great influence on the health and living environment of animals and plants.

Nitrogen oxides exist in the form of NO, NO ₂ , N ₂ O, N ₂ O _4, etc. The biggest damage is the production of photochemical smog, which reacts with hydrocarbons in the presence of sunlight to produce photochemical oxides.

In addition, it is estimated that nitrogen oxide is converted into nitric acid and nitrate, which cause acid rain, as well as causing visual disturbance and greenhouse effect, and about 40% of acid rain is caused by nitrogen oxide. In addition, since nitrogen oxide has a strong adsorption performance of 20,000 times with respect to O ₂ in hemoglobin, it is known as a substance that can cause great harm when the concentration is increased, and efforts to reduce it are urgently required.

Nitrogen oxides continue to increase, and the NOx emission rate by fuel is 7% Gas, 64% Oil and 29% Coal. %, Industrial plants 30%, power plants 15%, and heating 6%.

Nitrogen oxides are discharged mainly at about 5% fuel NOx due to the combustion of nitrogenous components in fuel oil and prompt NOx generated near the flame surface in the presence of hydrocarbons. And thermal NOx generated during combustion between fuel and fuel oil.

In order to reduce the emission of nitrogen oxide which is the main cause of air pollution, many countries are legally regulated. In Japan, the limits for nitrogen oxide emissions from newly built large-scale gas, oil and coal-fired power plants are 60, 130 and 200 ppm, respectively. However, to achieve atmospheric NOx concentrations regulated by local governments, power plants operate below 15, 30 and 60 ppm, well below the regulatory level, and gas turbines operate below 5 ppm. European limits are 30-50, 55-75 and 50-100 ppm for power plants and 25 ppm for gas turbines.

In order to satisfy these regulations, methods for reducing nitrogen oxides are needed. Among them, the pretreatment technique using the combustion method includes reducing the amount of excess air, cooling the combustion section, lowering the air preheating temperature, recirculating the exhaust gas, and improving the structure of the burner and the combustion chamber. However, since these methods are not effective due to low NOx reduction efficiency, introduction of a post-treatment device is essential to effectively control them.

In addition, the wet method, such as absorbing water, hydroxide or carbonate solution, sulfuric acid, etc., has good efficiency. However, when a large amount of gas is treated, a huge amount of absorbent is required. The problem arises.

Even in the dry method, a method using an adsorbent such as molecular sieve or activated carbon is difficult to apply when the amount of nitrogen oxide to be adsorbed is increased by a method used when a small amount of nitrogen oxide is contained in the flue gas. have.

For this reason, current techniques for NOx removal from most combustion gases currently utilize selective catalytic reduction (SCR) techniques with external reducing agents.

The selective catalytic reduction process utilizes a catalyst bed or system to treat the flue gas stream through selective conversion (reduction) of NO x to N ₂ . The SCR process usually utilizes ammonia or urea decomposing to ammonia as a reducing reactant injected into the flue gas stream upstream prior to contact with the catalyst. In commercial applications, SCR systems can typically achieve NOx removal rates in excess of 60%.

In case of commonly used SCR catalyst, when urea solution is injected to the dosing module disposed at the front end to maintain the NOx purification performance at a certain level or more, the urea solution is thermally decomposed by the heat of the exhaust gas. Ammonia gas is produced, and the ammonia gas and the nitrogen oxide can react on the catalyst so that the nitrogen oxide can be changed to harmless nitrogen.

On the other hand, disadvantages include a system for supplying urea in the liquid state to the catalyst, and a large space is required because additional systems such as a container for storing the urea in the liquid state and an injection device are required. There is an economic disadvantage.

In addition, the conventional liquid urea system has a problem in that the urea is not vaporized and produced as a solid ammonium when the exhaust gas temperature is sprayed under the conditions of 200 ℃ or less because the liquid urea system has to inject the liquid and vaporize the heat from the exhaust gas . In addition, since urea needs to be supplied periodically from the outside, inconvenience and additional management costs are required.

[Preceding technical literature]

[Patent Documents]

(Patent Document 0001) KR 10-0665606 B1

The present invention has been made to solve the above problems, by firing a support on which ruthenium and iridium are supported, and pretreating with a gas containing sulfur, NOx reduction performance at low temperatures of 170 ~ 300 ℃ without introducing an external reducing agent An object of the present invention is to provide an improved deNOx catalyst, a preparation method thereof, and a method for reducing NOx.

The problem to be solved by the present invention is not limited to the problem (s) mentioned above, and other object (s) not mentioned will be clearly understood by those skilled in the art from the following description.

The deNOx catalyst having improved NOx reduction performance according to an exemplary embodiment of the present invention is characterized in that the support is calcined by carrying ruthenium and iridium on a support, and the surface is modified with a gas containing sulfur.

In one embodiment, the sulfur-containing gas is preferably at least one selected from the group consisting of sulfur dioxide (SO ₂ ), hydrogen sulfide (H ₂ S), and sulfur monoxide (COS).

In one embodiment, it is preferable that the ruthenium (Ru) is supported at 0.1 to 10 parts by weight with respect to 100 parts by weight of the support.

In one embodiment, it is preferable that the iridium (Ir) is supported at 0.1 to 10 parts by weight with respect to 100 parts by weight of the support.

Method for producing a deNOx catalyst with improved NOx reduction performance according to an embodiment of the present invention, (a) supporting ruthenium and iridium on a support; And (b) calcining the support on which ruthenium and iridium of step (a) are carried; And (c) reforming the support surface of step (b) with a gas containing sulfur.

In one embodiment, in the step (a), it is preferable that ruthenium is firstly supported on the support and then iridium is secondly supported.

In one embodiment, the step (c) is preferably performed for 1 to 10 hours at a temperature of 300 ~ 800 ℃.

In one embodiment, the step (d), it is preferable to modify the surface by flowing a gas containing sulfur to the support of the step (c).

In one embodiment, the sulfur-containing gas is preferably at least one selected from the group consisting of sulfur dioxide (SO ₂ ), hydrogen sulfide (H ₂ S), and sulfur monoxide (COS).

In the NOx reduction method using a deNOx catalyst having improved NOx reduction performance according to another embodiment of the present invention, exhaust gas discharged from a ship engine is supplied to a deNOx catalyst through an exhaust gas discharge pipe to reduce NOx in the exhaust gas. The deNOx catalyst is characterized in that the support surface is modified with a gas containing sulfur after calcining and supporting ruthenium and iridium on the support.

In one embodiment, the sulfur-containing gas, NOx using a deNOx catalyst, characterized in that at least one selected from the group consisting of sulfur dioxide (SO ₂ ), hydrogen sulfide (H ₂ S), and carbon monoxide (COS). Reduction Method.

In one embodiment, it is preferable that the ruthenium (Ru) is supported at 0.1 to 10 parts by weight with respect to 100 parts by weight of the support.

In one embodiment, it is preferable that the iridium (Ir) is supported at 0.1 to 10 parts by weight with respect to 100 parts by weight of the support.

Using the deNOx catalyst having improved NOx reduction performance according to the present invention, a manufacturing method thereof and a NOx reduction method, there is an advantage in that the removal efficiency of NOx present in the exhaust gas can be greatly improved even at a low temperature of 180 ° C. In particular, after aging under actual conditions of catalyst use, there is an effect that shows the superior performance over the existing deNOx system.

In addition, by modifying the surface of the deNOx catalyst with a gas containing sulfur, it is possible to improve the selectivity of the catalyst in the middle temperature region to further improve the nitrogen oxide reduction effect, and more effective in removing NOx of sulfur-containing exhaust gas. have.

In addition, unlike the urea water SCR, it is not necessary to introduce a separate external reducing agent to remove NOx present in the exhaust gas, thereby simplifying the apparatus and having economic advantages in installation cost, maintenance cost, and raw material cost. In particular, it is possible to give additional deNOx performance to LNT and DOC, or TWC, etc., beyond the range of conventional urea SCR, and also to reduce CO and hydrocarbons.

1 is a flow chart showing a method for producing a deNOx catalyst with improved NOx reduction performance according to an embodiment of the present invention.

Figure 2 shows the NOx removal efficiency before and after the surface modification of the catalyst prepared according to Example 1.

Figure 3 compares the removal efficiency of nitrogen oxides according to the concentration of SO _{2 in} the exhaust gas of the catalyst prepared according to Example 3.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention and to provide general knowledge in the technical field to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims.

Shapes, sizes, ratios, angles, numbers, and the like disclosed in the drawings for describing the embodiments of the present invention are exemplary, and the present invention is not limited thereto. Like reference numerals refer to like elements throughout.

In addition, in describing the present invention, if it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In the case where 'comprises', 'haves', 'consists of' and the like mentioned in the present specification are used, other parts may be added unless 'only' is used. In the case where the component is expressed in the singular, the plural includes the plural unless specifically stated otherwise.

In the case of the description of the positional relationship, for example, if the positional relationship of the two parts is described as 'on', 'upon', 'lower', 'next to', etc. Alternatively, one or more other parts may be located between the two parts unless 'direct' is used.

In the case of a description of a temporal relationship, for example, if the temporal after-degree relationship is described as 'after', 'following', 'after', 'before', etc. This may include non-consecutive unless' is used.

Each of the features of the various embodiments of the present invention may be combined or combined with each other, partly or wholly, and various technically interlocking and driving are possible, and each of the embodiments may be implemented independently of each other or may be implemented together in an association. It may be.

Prior to describing the present invention, a brief description will be given of an SCR system using ammonia (NH ₃ ) or ammonia precursor urea.

The SCR system is used to reduce NOx in exhaust gases generated during the operation of land plants, ships, and automobiles. For example, an SCR system is required to reduce nitrogen oxides in exhaust gas generated from an engine or a boiler of a ship subject to ship IMO regulation, or a boiler or an incinerator of a land plant. The SCR system is a NOx reduction system using a selective catalytic reduction method. The SCR system is configured to react NOx with a reducing agent while simultaneously reducing exhaust gas and a reducing agent in a catalyst to reduce the nitrogen and water vapor. Recently, there have been many efforts to improve the SCR system. In spite of such efforts, the specificity of ships or some land plants does not produce definite results.

In general, SCR systems use urea, which provides NH ₃ or NH ₃ as a reducing agent for NOx reduction. In addition, the SCR system uses a catalyst having an active temperature range of 200 ° C to 400 ° C. Therefore, in the conventional SCR system, a reheating system for heating the exhaust gas is installed in front of the casing of the SCR reactor in which the catalyst is installed in order to increase the reaction efficiency by matching the conditions of the active temperature range.

In addition, in the conventional SCR system, in order to reduce PM (Particle Material), dust, and fine dust contained in the exhaust gas that has been reacted in the SCR reactor, a dust collecting facility or the like is installed at the rear of the SCR reactor casing to occupy a large space. There is a problem.

In addition, the conventional SCR system has a weak function of removing hydrocarbons and carbon monoxide, which are harmful components, and thus, there is a problem in that an oxidation catalyst system or the like must be additionally installed in order to reduce overall harmful gases.

The present invention has been proposed to solve the above problems, by firing the support on which ruthenium and iridium are supported, and pretreatment with a gas containing sulfur, NOx removal efficiency is greatly increased at low temperatures of 170 ~ 300 ℃ without introducing a reducing agent An object of the present invention is to provide a deNOx catalyst having improved NOx reduction performance and a method of preparing the same.

Using the deNOx catalyst having improved NOx reduction performance according to the present invention, a manufacturing method thereof and a NOx reduction method, there is an advantage in that the removal efficiency of NOx present in the exhaust gas can be greatly improved even at a low temperature of 180 ° C. In addition, unlike urea SCR, there is an economic advantage because it does not need to introduce a separate reducing agent to remove NOx present in the exhaust gas.

In particular, it is possible to impart additional deNOx performance to LNT and DOC, or TWC, etc., beyond the scope of the existing urea SCR, and also to reduce CO and hydrocarbons.

The lean NOx trap (LNT) is a method of occluding NOx in the Lean region (lean combustion) and reducing the NOx occluded in the Rich region (rich combustion), and the three-way conversion (TWC) catalyst is a stoichiometric air, fuel Catalysts that reduce NOx, CO and HC in engines operating at or near conditions.

The deNOx catalyst having improved NOx reduction performance according to an embodiment of the present invention is characterized in that ruthenium and iridium are supported and calcined on a support, and the surface is modified with a gas containing sulfur.

The sulfur-containing gas may be at least one selected from the group consisting of sulfur dioxide (SO ₂ ), hydrogen sulfide (H ₂ S), and sulfur monoxide (COS), and specifically, may be sulfur dioxide (SO ₂ ).

In addition, the concentration of the gas containing sulfur is not limited, but may be preferably 0.0001 to 10%, specifically 0.001 to 5%. In addition, the deNOx catalyst having improved NOx reduction performance may be a modified surface of the catalyst at a wide temperature of 20 ~ 800 ℃.

By reforming the surface of the catalyst with a gas containing sulfur, the NOx removal efficiency at the low temperature of 170 ~ 300 ℃ can be greatly improved. In particular, the catalyst has the advantage of further improving the NOx removal efficiency of the exhaust gas containing sulfur, such as the exhaust gas discharged from the vessel.

According to an embodiment of the present invention, the deNOx catalyst having improved NOx reduction performance may provide that ruthenium (Ru) is loaded in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support.

According to one embodiment of the present invention, the deNOx catalyst having improved NOx reduction performance may provide that the iridium (Ir) is loaded in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support.

The firing may be fired for 1 to 10 hours at a temperature of 300 ~ 800 ℃, specifically may be fired at 400 ~ 750 ℃.

If the calcination temperature is less than 400 ℃, there is a disadvantage that can not impart activity to the catalyst, if it exceeds 750 ℃ there is a problem that the surface of the catalyst is deteriorated and the activity of the catalyst may be degraded, the above range is preferred.

It is preferable that the supporting amount of the iridium is in an appropriate range, but in order to sufficiently serve the purpose of increasing the NOx removal efficiency at low temperatures, it is preferable that the iridium is loaded in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the support. 0.1 parts by weight of the supported amount of iridium is the lowest supported amount for securing the activity of the catalyst. On the other hand, even if it carries more than 10 weight part, since the improvement of activity is insignificant and economically undesirable, the said range is preferable.

The iridium is an element of atomic number 77 and the element symbol is Ir. A transition metal belonging to group 9 (group 8B) in the periodic table together with cobalt (Co) and rhodium (Rh), one of the platinum group metals. Platinum group metals consist of five and six cycles of elements in groups 8, 9, and 10 of the periodic table: ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), palladium (Pd), and platinum ( 6 metal elements of Pt). Hard but less ductile and easily broken and difficult to machine. The mass is silver white, but the powder is black. The density is 22.56 g / cm at 20 ° C., next to osmium (density 22.59 g / cm) of all elements. Melting point is 2,446 ℃, boiling point is 4,430 ℃.

The iridium is one of the refractory metals having the highest corrosion resistance, and does not react with air, water, acid, or alkali at room temperature, and does not dissolve in aqua regia. When heated to 800 ° C or higher in air or reacted with oxidizing molten alkali, it becomes iridium dioxide (IrO ₂ ). IrO ₂ is dissolved in aqua regia and decomposes into elements at about 1,100 ° C or higher. It reacts with some molten salts and also with halogen elements at high temperatures. In compounds, oxidation states of -3 to +6 are present, but oxidation states of +3 and +4 exist in the most common state.

In addition, the iridium compounds may be used as a catalyst for various chemical reactions. For example, _{[IrI 2 (CO) 2]} - may be used as a catalyst in methanol (CH ₃ OH) to carbonylation (carbonylation) cationic bar step (Cativa Process) making acetic acid (CH ₃ COOH) by.

The amount of ruthenium supported is preferably in an appropriate range, but in order to sufficiently serve the purpose of increasing the NOx removal efficiency at low temperatures, it is preferable that ruthenium is loaded at 0.1 to 10 parts by weight with respect to 100 parts by weight of the support.

0.1 parts by weight of the ruthenium supported amount is the lowest supported amount for securing the activity of the catalyst. Even if it carries more than 10 weight part, since the improvement of activity is insignificant and economically undesirable, the said range is preferable.

Ruthenium, the element number 44, is a transition metal located at the center of the periodic table, and is one of the platinum group metals. Transition metals are elements filled with electrons in the d-electron shell, which are generally hard, strong, colored complexes of various oxidation states, and have a common catalytic activity.

However, in detail, there is a significant difference between the early-transition metal belonging to Group 7 of the periodic table and the late-transition metal belonging to Groups 9-11.

Ruthenium belonging to group 8 has a common property of both the front transition metal and the post transition metal. Ruthenium is a rare metal that ranks approximately sixth in the smallest abundance of elements on the planet, and produces very little annual output. Thus, for most people, ruthenium will be considered a very new element. Ruthenium is mainly used as an alloy in the metal industry, as a catalyst in the chemical industry, and as an electrical contact and a resistive material in the electronic industry. It is also used for decorative and wear resistant plating of fine jewelry. Ruthenium complexes are also expected to be anticancer drugs and photocatalysts used to convert solar energy.

In addition, the deNOx catalyst having improved NOx reduction performance according to an embodiment of the present invention may additionally support other precious metals in addition to ruthenium and iridium, thereby limiting this within a range of increasing the NOx removal efficiency.

In one embodiment of the present invention, the preferred additional catalyst components for the ruthenium and iridium may be one or more precious metals selected from the group consisting of platinum, rhodium, palladium, and silver.

Particularly preferred among these additional precious metals may be platinum, rhodium and silver, and the platinum, rhodium, and silver preferably contain 0.1 to 10 parts by weight based on 100 parts by weight of the support. The reason why the noble metal should be included within the above range is to exert the supporting effect of the additionally supported precious metal and not to deteriorate the properties of the main components ruthenium and iridium. In addition, these additional precious metals may be supported in plural, for example, two kinds of precious metals of platinum and rhodium may be additionally supported with respect to iridium and ruthenium.

Platinum belongs to a rare element and ranks 74th in Clark number, and is produced as an alloy with a free state or other cognate elements, and is mainly produced in Russia, Ural, South Africa, Colombia, Canada and the like. Purity is 75 to 85% and impurities are other platinum group elements.

It is a silver-white noble metal, harder than silver, and has malleability and ductility. Cold work can also be done, but usually heated to 800 ~ 1,000 ℃. Adding a small amount of iridium can be a harder and stronger alloy while retaining the benefits of pure platinum. The expansion rate is almost the same as that of glass, which is convenient for joining glass appliances. Fine powdered platinum absorbs hydrogen at least 100 times its volume, and glowing platinum absorbs and permeates hydrogen. It is very stable to air and moisture and does not change even when heated to high temperature, and is resistant to acids and alkalis and has high corrosion resistance. However, it slowly melts in aqua regia and erodes when heated to high temperature with caustic alkali. It reacts when heated with fluorine, chlorine, sulfur, selenium and the like.

Rhodium is an element of atomic number 45, and the element symbol is Rh. It is a silvery white shiny transition metal, one of the platinum group metals. Usually produced and sold forms are blackish brown in powder or sponge form. In the periodic table, together with cobalt (Co) and iridium (Ir), they belong to group 9, and the elements of groups 8 to 10 are also called group 8B elements. Physical and chemical properties are closer to iridium or other platinum group metals than cobalt. It has a higher melting point and lower density than platinum. It is hard and does not wear well, and has a high reflectance of light, it does not oxidize at room temperature in air, and slowly oxidizes above 500 ° C to form rhodium oxide (Rh ₂ O ₃ ), but when heated further, it is decomposed into metal rhodium and oxygen again. . At high temperatures it reacts with sulfur and halogens. Insoluble in most acids, including nitric acid.

The palladium is a rare element of the 71st Clark number, but more than platinum or gold. It is an alloy in platinum, gold and silver ores. It is a white metal, the lightest of the platinum group metals and the lowest melting point metal. It is malleable and ductile and alloys with almost all metals. The metal has the property of absorbing a large amount of gas, especially hydrogen, which absorbs about 850 times hydrogen at room temperature and atmospheric pressure, with a marked expansion. When the hydrogen is released in a vacuum, it is as active as generator hydrogen. It is relatively reactive among the platinum group elements, so it is easy to be eroded by acid and is well soluble in aqua regia. Mild heating in oxygen produces oxides, but does not change in humid air or ozone at room temperature.

The silver is generally an off-white metal but also gray in powder. The second malleable and ductile property of metals, followed by gold, can produce very thin silver foils. In addition, it transfers heat and electricity best and has very good processability and mechanical properties. Metals such as silver, gold and platinum do not react easily with air or water. It reflects light well and is often used to make jewelry, and it is also called precious metal because the output is expensive due to its low output. The malleable and ductile metals are followed by gold, which, when melted, occludes large amounts of oxygen in the air and releases them violently when solidified. Thermal and electrical conductivity is the largest of the metals. It is stable in water and air, and does not rust very well, but turns to black silver peroxide in ozone and black silver sulfide in sulfur or hydrogen sulfide. It does not dissolve in normal acids or alkalis, but it dissolves in nitric acid and warm sulfuric acid, and nitric acid becomes silver sulfate, and the oxidation number of ordinary compounds is present in +1 and +2 valences.

In the deNOx catalyst having improved NOx reduction performance according to an embodiment of the present invention, a mixture of ruthenium and iridium may be supported on the support, and the support may be primarily supported on ruthenium and then secondly supported on iridium. Can be.

The reason why ruthenium is primarily supported on the support and then iridium is secondly supported is to prevent the iridium from being supported first.

When the support is first supported on iridium and then on ruthenium, iridium and ruthenium are separately present due to the strong interaction between the iridium and the support, and thus synergistic effects of iridium and ruthenium cannot be expected. When the support is first supported on ruthenium and then supported on iridium, strong support between the support and iridium may be prevented, and iridium and ruthenium may be present in close proximity, thereby improving low temperature performance.

In addition, even when the support is supported on the iridium and ruthenium mixture, the iridium and ruthenium mixture may be in close proximity to exhibit a low temperature performance enhancing effect. That is, the present invention is a catalyst for removing NOx in exhaust gas, and is an exhaust gas NOx reduction catalyst formed by simultaneously supporting and firing iridium and ruthenium in order to support the support, ruthenium and iridium or iridium first. .

The support may be one selected from the group consisting of aluminum oxide, zirconia, titania, silica, zeolite, ceria, and ceria-based multicomponent compounds, and specifically, may be aluminum oxide. In this case, the support may be monolithized to be supported on the iridium and ruthenium precursor solutions to form a catalyst layer.

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

The specific surface area of the said aluminum oxide is 5 m ² / g or more, specifically 50 m ² / g or more, and more preferably 100 m ² / g or more.

When the specific surface area of the aluminum oxide is small, 5 m ² / g or less, there is a disadvantage that the activity of the catalyst is inferior, the above range is preferable.

The aluminum oxide is generally called alumina and is colorless or white insoluble in water. α-alumina is a product of the Bayer method. Melting Point 1,999 ~ 2,050 ℃. β-alumina is said to be a stable form at high temperatures (above 1,500 ° C). (gamma) -alumina is obtained by heating and dehydrating a hydrate or (alpha) -hydrated alumina, and also maintaining it at 900 degreeC, and when it is 1000 degreeC or more, it has the characteristic of transition to alpha-alumina.

The aluminum oxide exhibits high specific surface area and good heat resistance to calcination at elevated temperatures, and is therefore preferred for use as a support for catalysts.

However, the aluminum oxide strongly interacts with sulfur and sulfur compounds present in the fuel and exhaust gas products, so that SO ₄ can be adsorbed on the surface of the aluminum oxide. When adsorbed in that way, sulfur compounds can shorten the life of common noble metal catalysts.

The zirconia is zirconium oxide (IV) (ZrO ₂ ), and is normally used as stabilized zirconia as an industrial material. It has a molecular weight of 123.22 and a melting point of about 2,700 ° C. The refractive index is large and the melting point is high, so the corrosion resistance is large. It does not dissolve in water, but dissolves in sulfuric acid and hydrofluoric acid. It can withstand rapid temperature change and can be used for equipment of rapid quenching and quenching.

The titania is an oxide of titanium, and absorbing ultraviolet rays can produce oxygen in the air or active oxygen having a strong oxidizing power in water. Because of this, it can act as an anti-pollution action, air purification action, antibacterial action, and environmentally friendly photocatalyst which is attracting attention these days.

Silica is a chemical combination of silicon and oxygen (SiO ₂ ), and in nature, silica is composed of five homogeneous crystals (quartz, tridymite, cristobalite, coesite, stishovite), chalcedony, amorphous, and hydrated (opal). It exists in various forms.

The zeolite is also referred to as zeolite and has many kinds but commonalities such as high water content, crystal properties, and acid phase. Hardness does not exceed 6, specific gravity is about 2.2. Generally it is colorless transparent or white translucent. In addition, since the bond of each atom is loosely crystallized structurally, even if the moisture filling the space is released at high heat, the skeleton remains the same, so that other particulates can be adsorbed and used as a support for the catalyst.

According to an embodiment of the present invention, the deNOx catalyst having improved NOx reduction performance may be calcined for 1 to 10 hours at a temperature of 300 to 800 ° C.

Only when the calcination temperature is 300 ° C. or higher can be used to increase the NOx removal efficiency at low temperatures, and when the calcination temperature is 800 ° C. or lower, a deNOx catalyst with improved NOx reduction performance can be provided at low temperatures.

When the calcination temperature is higher than 800 ° C., the catalyst component may be volatilized, and the catalytic activity point may be reduced by calcination, thereby decreasing performance. In addition, a problem that a large energy consumption due to high temperature may occur, so the above range is preferable.

The firing may be carried out under atmospheric pressure such as hydrogen, argon and air, but is not limited thereto.

According to one embodiment of the present invention, the deNOx catalyst having improved NOx reduction performance may be any one selected from the group consisting of TWC, LNT, and SCR catalysts.

Hereinafter, a method for preparing a deNOx catalyst having improved NOx reduction performance according to an embodiment of the present invention will be described in detail with reference to FIG. 1.

Method for producing a deNOx catalyst with improved NOx reduction performance according to an embodiment of the present invention, (a) supporting the ruthenium and iridium on the support (S100); And (b) calcining the support on which ruthenium and iridium of step (a) are carried (S200); And (c) reforming the support surface of step (b) with a gas containing sulfur (S300).

In the method for producing a deNOx catalyst having improved NOx reduction performance according to an embodiment of the present invention, step (a) (S100) is a step (S100) of supporting ruthenium and iridium on a support.

In the step (a), the ruthenium and iridium mixture may be prepared and supported at the same time, and ruthenium may be firstly supported on the support, and then iridium may be secondly supported.

The reason for preparing the ruthenium and iridium mixture to support the support is to prevent the support of iridium on the support first. If iridium is first supported on the support, synergistic effects of iridium and ruthenium cannot be expected due to the strong interaction between the iridium and the support. In addition, when ruthenium and iridium are supported on the support, two components must be present in close proximity to achieve low temperature performance.

According to an embodiment of the present invention, the support may be one selected from the group consisting of aluminum oxide, zirconia, titania, silica, zeolite, ceria, and ceria-based multicomponent compounds, and specifically, may be aluminum oxide. . In this case, the support may be monolithized to be supported on the iridium and ruthenium precursor solutions to form a catalyst layer.

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

The specific surface area of the aluminum oxide used as the support in step (a) (S100) is 5 m ² / g or more, specifically 50 m ² / g or more and more specifically 100 m ² / g or more desirable.

When the specific surface area of the aluminum oxide, which is the support, is less than 5 m ² / g or less, there is a disadvantage in that the activity of the catalyst is deteriorated.

The ruthenium (Ru) of the step (a) (Su), may be carried in 0.1 to 10 parts by weight, preferably in 1.5 parts by weight with respect to 100 parts by weight of the support.

The carrying amount of ruthenium is preferably in an appropriate range. Specifically, in order to sufficiently exhibit the purpose of increasing the NOx removal efficiency at low temperatures, the loading amount of ruthenium is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the support.

If the ruthenium is contained less than 0.1, the effect of removing NOx in the exhaust gas is insignificant, and if the ruthenium is included in excess of 10 parts by weight, there is a fear that the activity of iridium is suppressed, the above range is preferable.

After carrying out ruthenium on the support in step (a) (S100) it may further comprise the step of firing the ruthenium-supported support for 1 to 10 hours at a temperature of 300 ~ 800 ℃.

The reason for firing after ruthenium is supported on the support is that ruthenium is supported on the support so as not to be released.

The support is added to a ruthenium solution and supported, and then calcined at 300 to 800 ° C. for 1 to 10 hours to prepare a ruthenium-supported support first. Preferably, with respect to 100 parts by weight of the support, ruthenium may comprise 1.5 parts by weight.

In addition to the ruthenium in step (a) (S100), a catalyst component may be further included, and the preferred catalyst component may be at least one selected from the group consisting of platinum, rhodium, palladium, and silver. Particularly preferred among these additional precious metals are platinum, rhodium and silver. In this case, it is preferable that platinum carries 0.1-10 weight part with respect to the support amount of platinum, rhodium, and silver with respect to 100 weight part of said support bodies. In addition, it is preferable that the supporting amount of rhodium and silver also contains 0.1-10 weight part with respect to 100 weight part of said support bodies, respectively. In order to exert the effect of supporting an additional precious metal similarly to the above, in order not to reduce the characteristic of ruthenium which is a main component. Moreover, these additional metals may be supported on a plurality.

In the step (a) (S100) it may be supported on the support on which ruthenium is supported iridium.

Here, the supported amount of the iridium (Ir) may include 0.1 to 10 parts by weight, specifically, 1.5 parts by weight based on 100 parts by weight of the support. The 0.1 part by weight is the minimum supported amount for securing the activity of the catalyst. On the other hand, even if it carries more than 10 weight part, since the improvement of activity is insignificant, since it is economically undesirable, the said range is preferable.

A catalyst component may be further included in addition to the iridium, and the preferred catalyst component may be at least one selected from the group consisting of platinum, rhodium, palladium, and silver. Particularly preferred among these additional precious metals are platinum, rhodium and silver. In this case, it is preferable that platinum contains 0.1-10 weight part with respect to 100 weight part of said support bodies with respect to platinum, rhodium, and silver. In addition, the supported amount of rhodium and silver also preferably contains 0.1 to 10 parts by weight based on 100 parts by weight of the support. In order to exhibit the effect of supporting an additional precious metal similarly to the above, and to prevent the characteristic of the iridium which becomes a main component from degrading. Moreover, these additional metals may be supported on a plurality.

In the method for producing a deNOx catalyst with improved NOx reduction performance according to an embodiment of the present invention, the step (b) (S200), the (a) step 100 to burn the support on which ruthenium and iridium is supported Step S200.

The step (b) (S200) may be performed for 1 to 10 hours at a temperature of 300 ~ 800 ℃.

When (b) the sintering temperature of step (S200) is performed at 300 ° C. or lower, there is a disadvantage in that low-temperature activity of the resulting catalyst is lowered. When the calcination temperature is performed at 800 ° C. or higher, catalyst components may be volatilized and calcined. By this, the catalytically active point can be reduced, thereby reducing the performance. In addition, high energy consumption due to high temperature.

In the method for producing a deNOx catalyst with improved NOx reduction performance according to an embodiment of the present invention, the step (c) (S300), the (b) step (S200) of reforming the surface of the support with a gas containing sulfur Step.

The step (c) (S300), by flowing a gas containing 0.0001 ~ 10% sulfur to the support of the step (b) (S200) to modify the surface, specifically, 0.001 ~ 5 at 20 ~ 800 ℃ The surface may be modified by flowing a gas containing% sulfur.

The sulfur-containing gas may be at least one selected from the group consisting of sulfur dioxide (SO ₂ ), hydrogen sulfide (H ₂ S), and sulfur monoxide (COS), and specifically, may be sulfur dioxide (SO ₂ ).

In addition, the deNOx catalyst having improved NOx reduction performance may be modified on the surface of the catalyst at a wide range of temperature of 20 ~ 800 ℃.

The method for preparing a deNOx catalyst having improved NOx reduction performance as described above may include two methods of first supporting ruthenium on the support and then supporting iridium and supporting the mixture of ruthenium and iridium on the support.

The deNOx catalyst prepared according to one embodiment of the present invention may be any one selected from the group consisting of TWC, LNT and SCR catalyst.

In the NOx reduction method using a deNOx catalyst according to an embodiment of the present invention, the exhaust gas discharged from the ship engine is supplied to the deNOx catalyst through the exhaust gas discharge pipe to reduce NOx in the exhaust gas, and the deNOx catalyst is supported on the support. After carrying and calcining ruthenium and iridium, the surface of the support is modified with a gas containing sulfur.

Since the deNOx catalyst has been described above in the present invention, description thereof will be omitted.

According to one embodiment of the present invention can provide a deNOx system comprising the step of removing NOx with the catalyst described above.

DeNOx system according to an embodiment of the present invention, the diesel particulate filter for removing particulate matter in the exhaust gas flowing from the diesel engine; A diesel oxidation catalyst disposed between the diesel engine and the diesel particulate filter; And a NOx abatement device disposed behind the diesel particulate filter to decompose nitrogen oxides contained in the exhaust gas, wherein the NOx abatement device includes a deNOx system for removing nitrogen oxides from the exhaust gas that has passed through the diesel particulate filter. At least one catalyst prepared according to the present invention may be disposed therein.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. However, the following Examples and Experimental Examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example  One

First, 0.190 g of IrCl ₃ sample and 0.193 g of RuCl ₃ sample were simultaneously dissolved in water, and then supported on 5 g of γ-aluminum oxide, followed by drying at 100 ° C. for 12 hours. The dried γ-aluminum oxide was calcined at a temperature of 500 ° C. for 4 hours.

The catalyst was prepared by modifying the catalyst surface by flowing 20 ppm (0.002%) of sulfur dioxide (SO ₂₎ gas per hour after firing.

At this time, the ruthenium loading of the catalyst was 1.52 parts by weight based on 100 parts by weight of the total catalyst, and the loading of iridium was 2.11 parts by weight.

Example  2

First, 0.193 g of RuCl ₃ sample was dissolved in water, and then supported on 5 g of γ-aluminum oxide, which was dried at 100 ° C. for 12 hours.

The dried γ-aluminum oxide was calcined at a temperature of 500 ° C. for 4 hours. 0.190 g of IrCl ₃ sample was dissolved in water, and then supported on calcined γ-aluminum oxide and dried at 100 ° C. for 12 hours. The dried γ-aluminum oxide was calcined at a temperature of 500 ° C. for 4 hours.

After firing After the firing, 100 ppm (0.01%) of sulfur dioxide (SO ₂₎ gas was flowed to modify the surface of the catalyst to prepare a catalyst.

At this time, the amount of ruthenium supported by this catalyst is 1.52 parts by weight based on 100 parts by weight of the total catalyst, and the amount of iridium is 2.11 parts by weight.

Example  3

First, 0.190 g of IrCl ₃ sample and 0.193 g of RuCl ₃ sample were simultaneously dissolved in water, and then supported on 5 g of γ-aluminum oxide, followed by drying at 100 ° C. for 12 hours. After drying, the sample was calcined for 4 hours at a temperature of 500 ℃ to prepare a catalyst.

At this time, the amount of ruthenium supported by this catalyst is 1.52 parts by weight based on 100 parts by weight of the total catalyst, and the amount of iridium is 2.11 parts by weight.

Experimental Example  One

The removal efficiency of NOx according to the modification of the catalyst surface prepared according to Example 1 was confirmed.

Figure 3 shows the NOx removal efficiency before and after the surface modification of the catalyst prepared according to Example 1.

Referring to FIG. 3, when the surface of the catalyst is reformed with 20 ppm SO ₂ gas, the removal efficiency of NO is not improved, but the removal efficiency of NO 2 is greatly improved. Particularly, the catalyst is sent by flowing SO ₂ gas. It can be seen that the removal efficiency of NO ₂ is further improved when the surface is modified.

Experimental Example  2: Confirmation of nitrogen oxide removal efficiency according to SO2 concentration in exhaust gas

In Experimental Example 1, when the surface of the catalyst was modified with SO ₂ gas, it was confirmed that the removal efficiency of the nitrogen oxide was further improved. In Experimental Example 2, the nitrogen oxide in the exhaust gas containing the SO ₂ gas of the unmodified catalyst was improved. The removal efficiency of was confirmed.

The catalyst prepared according to Example 3 was measured for nitrogen oxide removal activity under the following measurement conditions.

SO ₂ : 20 ppm or 100 ppm

NOx: 50 ppm

CO: 0.7%

O ₂ : 5%

H ₂ O: 5%,

It was measured under the condition of N ₂ : balance and GHSV 200,000 h ⁻¹ , and the results are shown in FIG. 4.

Figure 4 compares the removal efficiency of nitrogen oxides according to the concentration of SO _{2 in} the exhaust gas of the catalyst prepared according to Example 3.

As shown in Figure 4, when the SO ₂ gas is included in the exhaust gas it can be seen that the removal efficiency of the NOx further improved at 170 ~ 300 ℃.

As a result, it can be confirmed that the deNOx catalyst having improved NOx reduction performance according to the present invention is more effective to be applied to an SCR system such as a ship that discharges exhaust gas having a high content of SO ₂ gas.

So far, the deNOx catalyst having improved NOx reduction performance according to an embodiment of the present invention and a specific embodiment related to the preparation method thereof have been described, but it is obvious that various modifications can be made without departing from the scope of the present invention. .

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

In other words, the foregoing embodiments are to be understood in all respects as illustrative and not restrictive, the scope of the invention being indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be construed as being included in the scope of the present invention.

Claims (13)

1. A deNOx catalyst with improved NOx reduction performance, characterized in that ruthenium and iridium are supported and calcined on a support, and the surface is modified with a gas containing sulfur.
2. The method of claim 1,

   The gas containing sulfur,

   DeNOx catalyst with improved NOx reduction performance, characterized in that at least one selected from the group consisting of sulfur dioxide (SO ₂ ), hydrogen sulfide (H ₂ S), and sulfur monoxide (COS).
3. The method of claim 1,

   The ruthenium (Ru), deNOx catalyst with improved NOx reduction performance, characterized in that supported by 0.1 to 10 parts by weight with respect to 100 parts by weight of the support.
4. The method of claim 1,

   The iridium is deNOx catalyst with improved NOx reduction performance, characterized in that supported by 0.1 to 10 parts by weight with respect to 100 parts by weight of the support.
5. (a) supporting ruthenium and iridium on a support; And

   (b) calcining the support on which ruthenium and iridium of step (a) are carried; And

   (c) reforming the surface of the support of step (b) with a gas containing sulfur; and a method for producing a deNOx catalyst having improved NOx reduction performance, comprising: a.
6. The method of claim 5,

   In step (a),

   A method for producing a deNOx catalyst having improved NOx reduction performance, characterized in that ruthenium is firstly supported on the support and then iridium is secondly supported.
7. The method of claim 5,

   In step (b),

   Method for producing a deNOx catalyst with improved NOx reduction performance, characterized in that carried out for 1 to 10 hours at a temperature of 300 ~ 800 ℃.
8. The method of claim 5,

   In step (c),

   The method for producing a deNOx catalyst having improved NOx reduction performance, characterized in that to modify the surface by flowing a gas containing sulfur to the support of step (b).
9. The method of claim 5,

   The gas containing sulfur,

   A method for producing a deNOx catalyst with improved NOx reduction performance, characterized in that at least one selected from the group consisting of sulfur dioxide (SO ₂ ), hydrogen sulfide (H ₂ S), and sulfur monoxide (COS).
10. The exhaust gas discharged from the ship engine is supplied to the deNOx catalyst through the exhaust gas discharge pipe to reduce the NOx in the exhaust gas,

    The deNOx catalyst,

    A method for reducing NOx using a deNOx catalyst, characterized in that after supporting ruthenium and iridium on a support and baking, the surface of the support is modified with a gas containing sulfur.
11. The method of claim 10,

    The gas containing sulfur,

    A method for reducing NOx using a deNOx catalyst, characterized in that at least one selected from the group consisting of sulfur dioxide (SO ₂ ), hydrogen sulfide (H ₂ S), and sulfur carbon monoxide (COS).
12. The method of claim 10,

    The ruthenium (Ru), NOx reduction method using a deNOx catalyst, characterized in that supported by 0.1 to 10 parts by weight with respect to 100 parts by weight of the support.
13. The method of claim 10,

    The iridium (Ir) is 0.1 to 10 parts by weight based on 100 parts by weight of the support, characterized in that NOx reduction method using a deNOx catalyst, characterized in that.

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