DE112013004202T5 - purifying catalyst - Google Patents

Abstract

The present invention relates to an exhaust gas purifying catalyst containing C-Fe-Ce, and provides a novel exhaust gas catalyst capable of exhibiting stable cleaning performance even when the flow rate of an exhaust gas changes while maintaining durability as broad temperature changes having. There is proposed an exhaust gas purifying catalyst having a configuration in which a mixture containing carbon (C), iron (Fe) and (cerium) is supported by an inorganic porous powdery carrier and which is characterized in that the content of the Mixture relative to the inorganic, porous, powdery carrier 10-300 wt .-% is.

Description

Technical area

The present invention relates to an exhaust gas purifying catalyst which is useful in purifying exhaust gas discharged from an internal combustion engine.

background

The exhaust gas of a motor vehicle which uses gasoline as fuel contains harmful components such as hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NO _x ). It is necessary to purify each of these harmful components using a catalyst so that the hydrocarbons (HC) are converted into water and carbon dioxide by oxidation, the carbon monoxide (CO) is converted into carbon dioxide by oxidation, and the nitrogen oxides (NO _x ) by reduction be converted into nitrogen.

As such a catalyst for treating exhaust gas (hereinafter referred to as "exhaust purification catalyst"), a three-way catalyst (TWC) capable of oxidizing CO and HC and reducing NO _{x was} used. The three-way catalyst is generally mounted in the form of a transducer in a middle position between the engine and the muffler of the exhaust pipe.

As such a three-way catalyst, there is known a three-way catalyst which comprises loading a noble metal such as platinum (Pt), palladium (Pd) or rhodium (Rh) onto a heat-resistant porous oxide body having a high specific surface area such as a porous alumina body having a high specific surface, and its subsequent loading on a substrate, such as a heat-resistant ceramic substrate or a monolithic substrate with a metal honeycomb structure or on a heat-resistant particles is obtained.

The noble metal in this kind of three-way catalyst has a function by which the hydrocarbons in the exhaust gas are oxidized into water and carbon dioxide by oxidation, carbon monoxide in the exhaust gas is converted into carbon dioxide by oxidation; In the meantime, the nitrogen oxides in the exhaust gas are converted by reduction into nitrogen. It is preferred that the ratio of fuel to air (air to fuel ratio) be kept constant (on the theoretical air to fuel ratio) to effectively promote catalysis for both reactions at the same time.

The air-fuel ratio of internal combustion engines of a motor vehicle and the like drastically changes depending on driving conditions such as acceleration, deceleration, low-speed driving, and high-speed driving, and thus the fluctuating air-fuel ratio (FIG. A / F) is constantly controlled by the operating conditions of the engine using an oxygen sensor (zirconia). However, it is not possible for the catalyst to exert sufficient purifying catalytic performance only by controlling the air-fuel ratio (A / F) as described above, and thus the catalyst layer itself should also have the effect of reducing the air-fuel ratio. Ratio (A / F). Therefore, a catalyst is used in which a promoter is added to a noble metal of the catalytic component for the purpose of preventing a decrease in the purification performance of the catalyst caused by a change in the air-fuel ratio by the chemical action of the catalyst itself.

As such a promoter, there is known a promoter (referred to as an "OSC material") having the oxygen storage capacity (OSC) to release oxygen in a reducing atmosphere and to absorb oxygen in an oxidizing atmosphere. For example, ceria (CeO ₂ ceria) or ceria-zirconia composite oxides are known as OSC material having this oxygen storage capacity.

However, the price of the noble metals is so high as to say that the price of the catalyst is largely due to the noble metals, and thus the development of a new catalyst component has been carried out to replace the noble metals.

For example, in Patent Document 1 ( JP 2005-296735 A ) discloses a catalyst in which iron oxide is loaded on a support containing a ceria-zirconia composite oxide.

In addition, in Patent Document 2 ( JP 2004-160433 A ) discloses a catalyst composed of a composite oxide of at least one kind of metal selected from the group consisting of ceria, zirconia, aluminum, titanium and manganese, and iron.

In Patent Document 3 ( JP 2008-18322 A ) discloses a catalyst having a structure in which iron oxide is dispersed in a ceroixd-zirconia composite oxide and at least partially in a solid solution state.

Further, an exhaust gas purifying catalyst composed of carbon (C) iron (Fe) cerium (Ce) in Patent Document 4 ( JP 2012-50980 A ) disclosed.

CITATION

Patent document

• Patent Document 1: JP 2005-296735 A
• Patent Document 2: JP 2004-160433 A
• Patent Document 3: JP 2008-18322 A
• Patent Document 4: JP 2012-50980 A

Disclosure of the invention

Task to be solved by the invention

A catalyst for a motor vehicle should have a performance capable of exhibiting a stable cleaning performance despite a change in the flow rate of the exhaust gas, in addition to durability against a large change in temperature. There is a tendency that the surface of the exhaust gas purifying catalyst decreases by sintering and hence the catalytic activity decreases when the exhaust gas purifying catalyst is heat-treated at a high temperature of 900 to 1000 ° C in air for a long time to ensure its durability. In particular, there is a problem of strong sintering tendency in a C-Fe-Ce catalyst having a high catalytic activity.

Accordingly, the object of the invention relates to an exhaust gas purifying catalyst containing C-Fe-Ce, and is to provide a novel exhaust gas catalyst having a power capable of stable cleaning performance despite a change in the flow rate of the exhaust gas. in addition to showing durability against a strong change in temperature.

Means of solving the task

In order to achieve the above object, the invention provides an exhaust gas purifying catalyst having a structure in which a mixture containing carbon (C), iron (Fe) and cerium (Ce) is charged on an inorganic porous powdery carrier.

Effect of the invention

The exhaust gas purifying catalyst proposed by the invention is obtained by charging a mixture containing carbon (C), iron (Fe) and cerium (Ce) onto an inorganic porous powdery carrier, and thereby sintering thereof, even if the exhaust gas purifying catalyst of FIG high temperature of 900 to 1000 ° C is suppressed. As a result, the exhaust gas purifying catalyst proposed by the invention has a high durability and can exert a stable cleaning performance at a high level despite a change in the flow rate of the exhaust gas.

As a reason why the sintering is suppressed even if the exhaust gas purifying catalyst is exposed to a high temperature as described above, it can be considered that there are a large number of fine pores on the surface of the inorganic porous powdery carrier, and in that the mixture containing carbon (C), iron (Fe) and cerium (Ce) is in a state of penetrating into each of these pores, thus inhibiting contact with an adjacent mixture, as a result of sintering is prevented. In addition, it can be considered that the mixture containing carbon (C), iron (Fe) and cerium (Ce) in the inorganic porous powdery carrier is dispersed and thus the effective reaction area is increased, as a result, a stable cleaning performance can be exercised despite a change in the flow rate of the exhaust gas.

Brief description of the figures

1 Fig. 12 is a schematic diagram of an apparatus for measuring the concentration of a model gas used in the performance test of a catalyst of Examples;

2 is a schematic diagram of a reaction tube in the device of 1 ; and

3 Fig. 12 is a graph illustrating the measured values of T50 in the examples as a ternary composition isoactivity diagram with carbon + iron, cerium, and alumina as the vertices.

Type (s) for carrying out the invention

Next, embodiments for carrying out the invention will be described. However, the invention is not limited to the embodiments described below.

purifying catalyst

The exhaust gas purifying catalyst as an example of the embodiments of the invention (referred to as "the present catalyst") is an exhaust gas purifying catalyst having a structure in which a mixture containing carbon (C), iron (Fe) and cerium (Ce) on an inorganic porous catalyst , powdered carrier is loaded.

As the above mixture containing carbon (C), iron (Fe) and cerium (Ce), a mixture containing iron carbide (Fe ₃ C), iron oxide and cerium oxide may be exemplified here.

At this time, each of the iron carbide (Fe ₃ C), iron oxide and cerium oxide serves as an active site which exerts an oxidation and reduction action. Among them, Fe ₃ C exerts high activity as an active site which exerts an oxidation and reduction effect. On the other hand, however, a simple substance of Fe ₃ C has low heat resistance, and therefore, most Fe ₃ C is oxidized to an oxide such as Fe ₂ O ₃ when subjected to a durability treatment at 900 to 1000 ° C and its activity generally deteriorates significantly as a result. However, the present catalyst is obtained by charging a mixture containing iron carbide (Fe ₃ C), iron oxide and cerium oxide on an inorganic porous powdery carrier, and as a result, can exert high catalytic activity even after such a preservability treatment.

In the present catalyst, the content of the mixture with respect to the inorganic porous powdery carrier (100% by weight) is preferably from 10.0 to 300% by weight, among which it is more preferably 20.0% by weight. % or more or 180% by weight or less, and more preferably, it is 30% by weight or more or 120% by weight or less.

In the present catalyst, it is possible to prevent the composite carbonate particles from being in close contact with each other and to prevent sintering from being exposed to a high temperature when the content of the mixture is in relation to the inorganic, porous, powdery Carrier is 300 wt% or less. It follows that it is possible to suppress a drop in the power rate caused by a drop in the effective area. On the other hand, it is possible to maintain the number of catalyst particles and maintain the performance rate by the presence of the effective active site when the content is 10.0 wt% or more.

In addition, the mass ratio of C atom to Fe atom to Ce atom (C: Fe: Ce) contained in the mixture is preferably 0.01 to 1.4 wt%: 0.1 to 98, 9 wt%: 0.1 to 98.9 wt% with respect to the total amount of C, Fe and Ce (100 wt%).

From this point of view, the content of carbon (C) is preferably 0.01 to 1.4% by weight with respect to the total amount of C, Fe and Ce (100% by weight), and under this, it is more preferably 0, 3% by weight or more or 1.3% by weight or less.

The content of iron (Fe) is preferably 0.1 to 98.9 wt% with respect to the total amount of C, Fe and Ce (100 wt%), and more preferably 7.8 wt. % or more, or 98.7% by weight or less, and more preferably, it is 26.7% by weight or more or 90.8% by weight or less. The content of cerium (Ce) is preferably 0.1 to 98.9% by weight with respect to the total amount of C, Fe and Ce (100% by weight), and under this, it is more preferably 0.1% by weight. % or more, or 92.1% by weight or less, and more preferably 7.9% by weight or more, or 73.0% by weight or less.

In addition, the mixture may further contain cobalt (Co). It is possible to improve the heat resistance by containing cobalt.

The content of cobalt is preferably higher than 0.1% by weight and lower than 15% by weight with respect to the total amount of C, Fe and Ce (100% by weight), and among them, it is particularly preferable it is 5 wt% or more or 10 wt% or less.

Inorganic Porous Powdery Carrier Examples of the inorganic porous powdery carrier may be an inorganic porous powdery carrier formed from a compound selected from the group consisting of a silica compound, an alumina compound, and a Titanium oxide compound or an OSC material such as a ceria-zirconia composite oxide.

In particular, it is possible to exemplify a porous powder formed from a compound selected from alumina, silica, silica-alumina, alumino-silicate, alumina-zirconia, alumina-chromia and alumina-ceria.

As the alumina, alumina having a specific surface area of more than 50 m ² / g, for example, γ, δ, θ or α alumina, may be preferably used. Among them, γ alumina or θ alumina is preferably used. At the same time, a trace amount of lanthanum (La) may be contained in the alumina to increase the heat resistance.

Examples of the OSC material may include a cerium compound, a zirconium compound and a ceria-zirconia composite oxide.

Other components

The present catalyst may be a catalyst having a structure in which, in addition to the mixture, a noble metal is loaded on an inorganic porous powdery carrier.

The loaded amount of the noble metal is preferably 0.01% by weight or more with respect to the mass of the loaded catalyst powder (100% by weight), and below that, it is more preferably 0.41% by weight or more.

At this time, examples of noble metals may include palladium (Pd), platinum (Pt) and rhodium (Rh). Among them, particularly preferred are palladium (Pd) or platinum (Pt).

production method

Next, an example of a method for producing the present catalyst will be described. However, the manufacturing method is not limited to the following manufacturing method.

For example, the present catalyst can be prepared as follows. An inorganic porous powdery carrier is added to a solution of an iron compound and a cerium compound, and the iron compound and the cerium compound are attached to the inorganic porous powdery carrier. Thereafter, the resulting result is heated and calcined in the air to charge iron oxide and cerium oxide on the inorganic porous powdery carrier, and then the result obtained in an atmosphere of a reactive carbon-containing gas such as carbon monoxide (CO) - Gas heated.

At this time, examples of the method of attaching an iron compound and a cerium compound to an inorganic porous powdery carrier may include a method in which an inorganic porous powdery carrier is added to a solution of an iron compound and a cerium compound. Thereafter, a basic substance such as ammonia-water or sodium carbonate is added thereto dropwise with stirring to give a pH of 10 to 11, whereby a composite hydroxide of Fe and Ce or a composite carbonate salt is precipitated. The precipitate is washed with water and dried. However, the method is not limited to such a method. In addition, it is also possible to adopt a method in which the heating is carried out in an inert gas atmosphere in the simultaneous presence of a carbon-containing substance, in addition to a method in which the heating is carried out in a reactive carbon-containing gas atmosphere.

As described above, since the Fe compound and the Ce compound are attached to the inorganic porous powdery carrier in a solution state, Fe and Ce can penetrate into the fine pores, and thus it is possible for a catalyst to be significantly preferred Dispersion state is obtained.

In addition, not only is it possible to charge the mixture of iron oxide and ceria on the inorganic porous powdery carrier in a uniformly dispersed state, but also to uniformly disperse carbon (C) as iron carbide when heated in an atmosphere of a reactive carbonaceous one Gas, such as CO gas is performed, in other words, a CO treatment is carried out by the gas phase method.

Present catalyst structure

It is possible to produce an exhaust gas purifying catalyst structure (referred to as "present catalyst structure") by forming a catalyst layer containing the present catalyst on a substrate.

It is possible to prepare a catalyst structure, for example, by forming a catalyst layer on the surface of a substrate having a honeycomb (monolithic) structure, by wash coating or the like of a catalyst composition containing the present catalyst.

substratum

In the present catalyst structure, examples of the material of the substrate may include a heat-resistant material such as ceramics or a metal material.

Examples of the material of the ceramic substrate may include a heat-resistant ceramic such as cordierite, cordierite-alpha-alumina, silicon nitride, zirconium mullite, spodumene, alumina-silica-magnesia, zirconium silicate, sillimanite, magnesium silicate, zirconium, petalite, alpha-alumina, and an aluminosilicate ,

Examples of the material of the metallic substrate may include a refractory metal such as stainless steel or other suitable iron-based corrosion resistant alloys.

Examples of the substrate form may include a honeycomb shape, a pellet shape, and a spherical shape.

For example, as a honeycomb material, cordierite material such as ceramics is commonly used in general. In addition, it is also possible to use a honeycomb formed of a metal material such as ferritic stainless steel.

In the case of using a substrate having a honeycomb shape, it is possible to use, for example, a monolithic substrate having a large number of parallel and fine gas flow passages, namely, channels within the substrate so that the fluid flows through the inside of the substrate. At this time, it is also possible to form a catalyst layer by coating with a catalyst composition on the surface of the inner walls of each of the channels of the monolithic substrate by wash coating or the like.

catalyst composition

Further, if necessary, the catalyst composition for forming a catalyst layer of the present catalyst structure may contain, in addition to the present catalyst, a stabilizer or another component from above.

For example, it is possible to add a stabilizer for the purpose of suppressing the reduction of palladium oxide (PdO _x ) to metallic palladium in a propellant gas-rich atmosphere.

Examples of this type of stabilizer may include an alkaline earth metal or an alkali metal. Among them, it is possible to select one kind or two or more kinds of metals selected from the group consisting of magnesium, barium, calcium and strontium, and preferably strontium and barium. Among them, barium is preferable from the viewpoint that it has the highest temperature for the reduction of PdO _x , that is, it is scarcely reduced.

In addition, the catalyst composition may contain a known additive component such as a binder component.

As the binder component, it is possible to use an inorganic binder such as an aqueous solution such as alumina sol, silica sol or zirconia sol. These may be converted to the form of an inorganic oxide when calcined.

production method

As an example of the preparation of the present catalyst structure, it is possible to mix a process in which the present catalyst is added to water and stir by a ball mill or the like to obtain a slurry and a substrate such as a ceramic Honeycomb body or the like is dipped in this slurry, then the result thereof is taken out and calcined, thereby forming a catalyst layer on the surface of the substrate or the like, by way of example. However, the method for producing the present catalyst is not limited to the above example, and any known method may be used.

Explanation of terms

As used herein, the term "X to Y" (X and Y are any numbers) includes the meaning "preferably greater than X" or "preferably less than Y" and the meaning "X or greater and Y or less" unless otherwise specified indicated.

In addition, the term "X or more" (X is an arbitrary number) or "Y or less" (Y is any number) also includes the intention of "preferably more than X" or "preferably less than Y".

Examples

In the following, the invention will be described in more detail with reference to the following examples and comparative examples.

Examples 1 to 28 and Comparative Examples 1 to 10

Iron (II) nitrate (nonahydrate) and cerium (III) nitrate (hexahydrate) were dissolved in pure water, and then alumina powder (m001) or an OSC material (ceria-zirconia composite oxide) was added thereto while stirring. whereby a mixed solution was prepared.

At this time, the masses of iron (II) nitrate (nonahydrate), cerium (III) nitrate (hexahydrate), alumina powder and OSC material were adjusted so that the mass of the iron atom contained in the ferrous nitrate ( Nonahydrate), the mass of the cerium atom contained in the cerium (III) nitrate (hexahydrate), the mass of the alumina and the mass of the OSC material gave the composition shown in Table 1.

Next, ammonia water was added dropwise to the mixed solution until the pH thereof became 10 to 11, and the result was kept at a rotational speed of 3 hours for 3 hours Stirred from 600 rpm. Thereafter, the solution was filtered, and the precipitate was washed with water 2 to 3 times and then dried in a dryer at 120 ° C.

Subsequently, the thus-obtained precipitate was calcined at 500 ° C for 3 hours in an air atmosphere, then the result was ground using a mortar and heated at 525 ° C for 4 hours in a CO gas atmosphere to thereby produce a C-gas. Fe-Ce / alumina catalyst or a C-Fe-Ce / OSC material catalyst having a structure in which a mixture containing iron carbide (Fe ₃ C), iron oxide and ceria was loaded on alumina or an OSC material, to obtain.

Quantification method for each component

The mass of the iron atom, the mass of the cerium atom, the mass of aluminum oxide and the mass of the OSC material were the same as the blending amounts for each of them, and therefore their quantification was not particularly performed.

On the other hand, it was found that the amount of carbon was measured by a carbon and sulfur analyzer (manufactured by Horiba, Ltd.) and by multiplying the mixing amount by the C amount coefficient (19%) after a heat treatment at 500 ° C or higher and 1000 ° C or less can be determined. Furthermore, the amount of carbon by a pyrogenic reaction may decrease in some cases, and thus the amount of carbon after the durability treatment was measured at 1000 ° C for 5 hours, however, no change in the carbon amount before and after the durability treatment was observed because heating at 500 ° C or higher in the examples above. Table 1 C (% by weight) Fe (% by weight) Ce (wt .-%) m001 (wt%) OSC material (% by weight) Examples 1 to 4 0.25 18.25 18.55 62.94 Example 5 0.09 6.49 42.06 51,35 Example 6 0.09 6.49 42.06 51,35 Example 7 0.14 9.99 24.97 64.91 Example 8 0.24 17.80 13,60 68.36 Example 9 0.34 24.92 24.92 49.83 Example 10 0.41 29,88 9.96 59.76 Example 11 0.22 16.16 9.08 74.54 Example 12 0.22 16.36 32.33 51.09 Example 13 0.39 28.89 24.40 46.32 Example 14 0.40 29.48 2.59 67.53 Example 15 0.53 38.69 9.65 51.13 Example 16 0.13 9.19 25.07 65.62 Example 17 0.16 11.98 9.98 77.87 Example 18 0.68 49,66 0.00 49,66 Example 19 0.52 38.50 24.87 36.11 Example 20 0.04 3.20 37.38 59.37 Example 21 0.25 18.35 0.00 81.40 Example 22 0.75 54.79 0.00 44.47 Example 23 0.00 0.00 50,00 50,00 Example 24 0.63 45.91 26.23 27.23 Example 25 0.10 7.49 4.00 88.41 Example 26 0.86 63.15 0.00 35,99 Example 27 0.00 0.00 49,30 50,70 Example 28 0.00 0.00 16.40 83,60 Comparative Examples 1 to 4 0.99 17.72 81.29 Comparative Example 5 0.00 0.00 30.00 70,00 Comparative Example 6 0.00 0.00 100.00 0.00 Comparative Example 7 0.00 0.00 0.00 100.00 Comparative Example 8 0.68 49,66 49,66 0.00 Comparative Example 9 1.34 98.66 0.00 0.00

Durability Test Method

The exhaust gas purifying catalyst was treated under the durability conditions shown in Table 2 to examine the durability. Table 2 life conditions temperature 1000 ° C Time 5 hours gas condition Air (10s) ⇔ A / F 13.5 (20 s) A / F 13.5 texture C ₃ H ₆ 3333 ppmC O ₂ 0.105% H ₂ O 10% He rest

Procedure for performance test of the catalyst

The performance test of the catalyst was carried out using a model gas shown in Table 3. Table 3 Composition of the model gas O ₂ 1.0% NO 0.1% CO 1.0% C ₃ H ₆ 0.1% H ₂ 0.2% CO ₂ 8.0% H ₂ O 10.0% HE Base Air-fuel ratio A / F 14.63 (theoretical air-fuel ratio)

1 Fig. 12 is a schematic diagram illustrating an apparatus for measuring the concentration of the model gas containing NO _x , CO or H ₂ and C ₃ H ₃ as HC. 2 FIG. 12 is a schematic diagram illustrating the reaction tube which is a part of the top measurement apparatus. FIG.

As in 1 illustrated, the device is used for measuring by a standard gas cylinder 1 , a mass flow controller 2 , a water tank 3 , a water pump 4 , an evaporator 5 , a reaction tube 6 , a cooler 8th , a gas analyzer 9 and the like, operated as follows. First of all, each model gas will be from the standard gas cylinder 1 generated, the gases are mixed by the mass flow controller 2 , Water, which comes from the water pump 4 is introduced by the evaporator 5 vaporized and the respective gases are passed through the evaporator 5 merged and into the reaction tube 6 introduced. Thereafter, the reaction tube 6 containing the model gas through an electric heater 7 heated.

Each of the model gases is catalyzed by a catalyst 10 in the reaction tube 6 oxidized or reduced. The gas becomes after the reaction of a removal of the water vapor in the cooler 8th and then the composition thereof is determined by the gas analyzer 9 analyzed.

The gas analyzer 9 is capable of conducting the quantitative analysis of O ₂ , CO, N ₂ O, CO ₂ , HC (C ₃ H ₆ ), H ₂ or the like by gas chromatography. NO _x , NO, NO ₂ , CO or the like can be quantitatively analyzed by a NO _x analyzer.

The purification performance of the catalyst was determined as the conversion rate of each gas by the following formula for calculation using the measuring apparatus from above. Reaction rate NO _X = {(molar flow rate of NO + molar flow rate of NO ₂ at the inlet) - (molar flow rate of NO + molar flow rate of NO ₂ at the exit)} / (molar flow rate of NO + molar flow rate of NO ₂ at the entrance) × 100%

The present catalyst is prepared by heat treatment in a CO gas atmosphere, and thereby amorphous C is fixed on the surface, and as a result, in some cases, a C amount is measured as a mixing ratio which is larger than the stoichiometric carbon ratio of Fe ₃ C. Therefore, it is desirable to examine the catalyst subjected to the durability treatment to compare the stable catalytic performance.

Accordingly, the conversion rate of NO _x and the temperature (T50) at which the conversion rate of _NOx was 50% after the durability treatment were at 1000 ° C for 5 hours, if necessary, measured.

Examination of the effect of dispersing the C-Fe-Ce catalyst on alumina powder

Table 4 shows the results of measurement of temperature (T50) at which the reaction rate of NO _{x of} the catalyst obtained by dispersing C-Fe-Ce on the alumina powder becomes 50%. Table 4 C (% by weight) Fe (% by weight) Ce (% by weight) m001 (weight%) T50 (NO _x) SV value (ml / min.g) life conditions example 1 0.25 18.25 18.55 62.94 682 500 Available Example 2 0.25 18.25 18.55 62.94 348 500 Absent Example 3 0.25 18.25 18.55 62.94 1000 3000 available Example 4 0.25 18.25 18.55 62.94 510 3000 Absent Comparative Example 1 0.99 17.72 81.29 930 500 available Comparative Example 2 0.99 17.72 81.29 470 500 absent Comparative Example 3 0.99 17.72 81.29 1367 3000 available Comparative Example 4 0.99 17.72 81.29 694 3000 absent

It was confirmed that the catalyst dispersed on the alumina powder has a low T50 even after the durability treatment. It is considered that the reason for this is that the sintering is suppressed by the dispersion of the catalyst on the alumina. In addition, the results obtained by varying the SV value are also shown in Table 4. It was confirmed that the catalyst dispersed on the alumina has a low T50 even after a high SV value and its activity is high.

Investigation of the effect of dispersing the C-Fe-Ce catalyst on OSC material

Table 5 shows the results of measurement of temperature (T50) at which the conversion rate of NO _{x of} the catalyst obtained by the dispersion of C-Fe-Ce on an OSC material becomes 50%. Table 5 C (% by weight) Fe (% by weight) Ce (% by weight) m001 (weight%) OSC material (except Ce) T50 (NO _x) SV value (ml / min.g) life conditions Comparative Example 1 0.99 17.72 81.29 1300 ° C or higher 500 available Example 5 0.09 6.49 42.06 51,35 800 500 available Example 6 0.09 6.49 42.06 51,35 784 500 available

From the results of Table 5, it was confirmed that the catalyst obtained by dispersing C-Fe-Ce on an OSC material has a lower T50 than the catalyst obtained by dispersing C-Fe-Ce on the Alumina powder is obtained, and an apparently lower T50 than the catalyst, which is not obtained by dispersion on a support.

Examining the compositional range that exerts beneficial T50

The ratio of the catalyst after the durability treatment at 1000 ° C for 5 hours is shown in Table 6.

In addition, Table 6 also shows the results of measurement of temperature (T50) at which the conversion rate of NO _x becomes 50% by the above catalytic performance determination method. Table 6

A ternary composition isoactivity plot with carbon + iron, cerium and alumina as vertices was prepared from the measured T50 values in Table 6 using the OriginPro7.5 graphics software supplied by LightStone Corp. and the compositions in which the T50 was 725 ° C, 750 ° C, 775 ° C, 800 ° C, 850 ° C, 900 ° C and 950 ° C were merged by a line (isoactivity temperature line). The triangle diagram thus obtained is in 3 illustrated.

As a result, the ratio of the catalyst component (C + Fe + Ce) with respect to the alumina (100% by weight) is preferably from 12.3 to 268%, among which it is preferably from 21.4 to 177% by weight. and among these, it is particularly preferable from 34.4 to 116% by weight. In addition, the optimum composition having the lowest T50 was 18.50 wt%, 18.55 wt%, and 62.94 wt% for the (carbon + iron), cerium, and alumina, respectively.

From the above result, it can be considered that the content of the mixture with respect to the inorganic porous powdery carrier (100% by weight) is preferably 10.0 to 300% by weight, below this particularly preferably 20.0% by weight. % or more or 180% by weight or less, and below this most preferably 30.0% by weight or more or 120% by weight or less.

In addition, from the results described above and the results of the tests which have been carried out, it is considered that the content of carbon (C) is preferably 0.01 to 1.4% by weight with respect to the total amount of C, Fe and Ce (100% by weight), and under this, it is more preferably from 0.3 to 1.3% by weight. It can be considered that the content of iron (Fe) is preferably 0.1 to 98.9 wt% with respect to the total amount of C, Fe and Ce (100 wt%), among which particularly preferably 7 , 8 to 98.7 wt .-%, and under this very particularly preferably 26.7 to 90.8 wt .-% is. It can be considered that the content of cerium (Ce) is preferably 0.1 to 98.9% by weight with respect to the total amount of C, Fe and Ce (100% by weight), among which more preferably 0 , 1 to 92.1 wt .-%, and most preferably 7.9 wt .-% to 73.0 wt .-%.

Examples 29 to 31: Investigation of the Effect of Precious Metal Addition

The catalysts were prepared in the same manner as in Examples 1 to 28, except that the mass of the iron atom, the mass of the cerium atom and the mass of the alumina were changed to the ratios shown in Table 7. Thereafter, the catalyst powder thus obtained was stirred into a Pd nitrate solution, which was taken to have the charged amount of the noble metal shown in Table 7, for 3 hours at a rotation speed of 600 rpm and then dried in a dryer at 120 ° C. Subsequently, the result was calcined at 600 ° C for 3 hours in the air atmosphere, whereby a noble metal-loaded powdery catalyst (Examples 29 to 31) having a structure in which a mixture containing iron carbide (Fe ₃ C), iron oxide and ceria on alumina was loaded.

Table 7 shows the results of measuring the temperature (T50) at which the conversion rate of NO _x of the catalyst, which was obtained by the loading of Pd to the mixture of Example 1, 50%.

The T50 of the NO _x decreases with an increase in the amount of Pd loaded and it was thus confirmed that Pd contributes well to improving the performance of a catalytic converter.

Furthermore, this loaded amount of Pd is about a fraction of the amount normally charged on an exhaust gas purifying catalyst, and thus, this fact can simultaneously contribute to a decrease in the use amount of expensive Pd.

With this in mind, it is considered that the charged amount of a noble metal is preferably 0.01% by weight or more with respect to the charge catalyst powder (100% by weight), and below that, it is more preferably 0.41% by weight. % or more. Table 7 Pd (wt%) C (% by weight) Fe (% by weight) Ce (wt .-%) m001 (wt%) T50 (NOx) SV value (ml / min.g) life conditions example 1 0 0.25 18.25 18.55 62.94 682 500 available Example 29 0.073 0.25 18.24 18.54 62,90 393 500 available Example 30 0.41 0.25 18.18 18.48 62.68 348 500 available Example 31 0.66 0.25 18.13 18.43 62.53 329 500 available

Examples 32 to 34: Examination of the effect of co-addition

Iron (II) nitrate (nonahydrate), cerium (III) nitrate (hexahydrate) and cobalt nitrate were dissolved in pure water, and then an alumina powder (m001) was added while stirring, thereby preparing a mixed solution. The masses of iron (II) nitrate (nonahydrate), cerium (III) nitrate used (Hexahydrate), cobalt nitrate and aluminum powder were adjusted so that the mass of the iron atom contained in the ferrous nitrate (nonahydrate) was the mass of the cerium atom contained in the cerium (III) nitrate (hexahydrate). the mass of the cobalt atom contained in the cobalt nitrate and the mass of the alumina became the ratio shown in Table 8.

Next, an aqueous solution of sodium carbonate was added dropwise to the mixed solution until its pH was from 10 to 11, and the result was stirred for 3 hours at a stirrer rotation speed of 600 rpm.

Thereafter, the solution was filtered and the precipitate was washed with water 2 to 3 times and then dried in a dryer at 120 ° C. Subsequently, the resulting precipitate was calcined at 500 ° C for 3 hours in the air atmosphere, and the result was ground using a mortar and heated at 525 ° C for 4 hours in a CO gas atmosphere, whereby the C-Fe-Ce-Co / Alumina catalyst having a structure in which a mixture containing iron carbide (Fe ₃ C), iron oxide and cerium oxide was charged on alumina was obtained.

The ratio of C, Fe, Ce, Co, alumina and T50 of the NO _x is shown in Table 8 below. Table 8 Co (% by weight) C (% by weight) Fe (% by weight) Ce (wt .-%) m001 (wt%) T50 (NOx) SV value (ml / min.g) life conditions example 1 0 0.25 18.25 18.55 62.94 682 500 Available Example 32 5 0.24 17.34 17.63 59,80 504 500 Available Example 33 10 0.22 16.43 16.70 56.65 541 500 Available Example 34 15 0.21 15.52 15.77 53.50 780 500 Available

The T50 of NO _x decreases with an increase in the amount of Co added, but it increases when the amount of CO added exceeds a certain amount. With this result, it was confirmed that Co contributes to improving the performance of an exhaust gas catalyst.

Taking this aspect into consideration, it is considered that the content of Co is preferably more than 0.1% by weight and less than 15% by weight with respect to the catalyst material (100% by weight), and more preferably from 5 to 10% by weight.

Example 35: Effect of Co and Pt addition

Iron (II) nitrate (nonahydrate), cerium (III) nitrate (hexahydrate), and cobalt nitrate were dissolved in pure water, and then an alumina powder (m001) was added while stirring, thereby preparing a mixed solution. The masses of iron (II) nitrate (nonahydrate), cerium (III) nitrate (hexahydrate), cobalt nitrate and aluminum powder used were adjusted so that the mass of the iron atom contained in the iron (II) nitrate (nonahydrate), the Mass of the cerium atom contained in the cerium (III) nitrate (hexahydrate), the mass of the cobalt atom contained in the cobalt nitrate) and the mass of the alumina became the ratio shown in Table 9.

Next, an aqueous solution of sodium carbonate was added dropwise to the mixed solution until its pH was from 10 to 11, and the result was stirred for 3 hours at a stirrer rotation speed of 600 rpm. Thereafter, the solution was filtered and the precipitate was washed with water 2 to 3 times and then dried in a dryer at 120 ° C. Subsequently, the thus-obtained precipitate was calcined at 500 ° C for 3 hours in the air atmosphere, and the result was introduced into an aqueous solution of chloroplatinic acid and stirred for 3 hours, whereby platinum (Pt) was charged. The loaded amount of Pt is shown in Table 9. Thereafter, the result was further dried in a dryer at 120 ° C, calcined at 500 ° C for 3 hours in the air atmosphere, and then ground using a mortar. Thereafter, the result was heated at 525 ° C for 4 hours in a CO gas atmosphere, whereby a Pt / C-Fe-Ce-Co / alumina catalyst was obtained, with a structure in which Pt was loaded on a catalyst a mixture containing iron carbide (Fe ₃ C), iron oxide and ceria on alumina.

Example 36: Effect of Co and Pd addition

A Pd / C-Fe-Ce-Co / alumina catalyst was obtained in the same manner as in Example 35 except that an acetone solution of palladium acetate was used instead of the aqueous solution of chloroplatinic acid and palladium (Pd) was charged by vacuum drying in Example 35 has been. The loaded amount of Pd is shown in Table 9. Table 9 Pt Pd C Fe Co Ce m001 T50 SV life conditions (Wt .-%) (Wt .-%) (Wt .-%) (Wt .-%) (Wt .-%) (Wt .-%) (Wt .-%) (NO _x ) (Ml / min · g) Example 35 0.35 0 0.38 2.0 2.0 18.0 77.62 402 3000 available Example 36 0 0.35 0.38 2.0 2.0 18.0 77.62 383 3000 available

The T50 of NO exerted a low value even in a case where the SV value was even 3000 mL / min · g, and it was confirmed that the C-Fe-Ce-Co / alumina catalyst containing Pt or Pd was loaded, showing an advantageous performance even in a case where Pt or Pd was charged in only small amounts, which is about a fraction of the amount normally charged to an exhaust gas purifying catalyst.

LIST OF REFERENCE NUMBERS

1

Standard gas cylinder

2

Mass flow controller

3

water tank

4

water pump

5

Evaporator

6

reaction tube

7

electric heater

8th

cooler

9

Gas analyzer

10

catalyst

11

quartz sand

12

Quartz wool and

13

thermocouple

Claims (9)

An exhaust gas purifying catalyst comprising a composition having a mixture containing carbon (C), iron (Fe) and cerium (Ce) loaded on an inorganic porous powdery carrier. The exhaust gas purifying catalyst according to claim 1, wherein the mixture is a mixture including iron carbide (Fe ₃ C), iron oxide and cerium oxide. The exhaust gas purifying catalyst according to any one of claims 1 or 2, wherein the content of the mixture in relation to the inorganic porous powdery carrier (100% by weight) is from 10.0 to 300% by weight and the mass ratio of the C atom to Fe Atom to Ce atom (C: Fe: Ce) contained in the mixture, 0.01 to 1.4 wt%: 0.1 to 98.9 wt%: 0.1 to 98 , 9% by weight with respect to the total amount of C, Fe and Ce (100% by weight). The exhaust gas purifying catalyst according to any one of claims 1 to 3, wherein the mixture further includes cobalt (Co). The exhaust gas purifying catalyst according to any one of claims 1 to 4, wherein said inorganic porous powdery carrier is an inorganic porous powdery carrier containing alumina or a ceria-zirconia composite oxide. An exhaust purification catalyst according to any one of claims 1 to 5, wherein a noble metal is further loaded on the exhaust gas purifying catalyst. The exhaust gas purifying catalyst according to claim 6, wherein the noble metal is platinum (Pt) or palladium (Pd). An exhaust purification catalyst structure comprising a substrate and a catalyst layer including the exhaust purification catalyst according to any one of claims 1 to 7. A method of manufacturing an exhaust gas purifying catalyst, comprising: dissolving an iron compound and a cerium compound in a solution; the addition of an inorganic, porous, powdery carrier thereto and attaching the iron compound and the cerium compound to the inorganic porous powdery carrier, then charging the iron oxide and cerium oxide to the inorganic porous powdery carrier while heating and calcining the result in air and then; heating the result in a reactive carbon-containing gas atmosphere to obtain an exhaust gas purifying catalyst having a mixture containing carbon (C), iron (Fe) and cerium (Ce) loaded on an inorganic porous powdery carrier.

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