JP2010158669A - Exhaust gas purification catalyst, method for manufacturing the same, exhaust gas cleaning filter, method for manufacturing the same, and exhaust gas cleaning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas purification catalyst that reduces catalyst metal scattering in an atom or molecule level, a method for manufacturing the same, an exhaust gas cleaning filter, a method for manufacturing the same, and an exhaust gas cleaning device. <P>SOLUTION: The catalyst configured by supporting a first catalyst containing at least one kind of metallic element or more selected from copper, vanadium or molybdenum, a second catalyst containing an alkali metals, and a third catalyst containing an alkaline earth metal element on an inorganic oxide having heat resistance, wherein not only PM may be efficiently oxidized (combusted) but also a catalyst where catalyst metal scattering in an atom or molecule level may be reduced is obtained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification catalyst for burning particulate matter (hereinafter referred to as PM) contained in exhaust gas of a diesel engine, a method for producing the same, an exhaust gas purification filter, a method for producing the same, and an exhaust gas purification device. It is.

  Conventionally, in a method of purifying air by bringing a gas to be treated and a catalyst into contact with each other, a catalyst metal scattering countermeasure in the case of a fixed bed type is disclosed in Patent Document 1 as a catalyst scattering prevention network downstream of the catalyst. A method of collecting the scattered catalyst particles by providing a catalyst is used. In the case of the moving bed type, as disclosed in Patent Document 2, the gas processing capacity is reduced, but there is a method for reducing the amount of catalyst scattering by reducing the gas processing speed to 1.5 m / s or less. Has been taken.

Japanese Examined Patent Publication No. 59-29286 (Page 4, FIGS. 4 and 5) JP-A-8-24623 (page 6)

  Such conventional catalyst scattering countermeasures can physically collect the scattered catalyst particles with a net or filter, but cannot be collected with an ionic metal or the like that cannot be collected with a net or filter. There has been a problem that metal ions and the like are released into the atmosphere together with air since no countermeasures against scattering at the atomic or molecular level have been made.

  Therefore, the present invention solves the above-described conventional problems, and an exhaust gas purification catalyst with reduced catalyst metal scattering at the atomic or molecular level, a production method thereof, an exhaust gas purification filter, a production method thereof, and an exhaust gas It aims to provide a purification device.

  In order to achieve this object, the present invention provides a first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum using an inorganic oxide having heat resistance as a catalyst carrier, an alkali, This is an exhaust gas purification catalyst comprising a second catalyst containing a metal element and a third catalyst containing an alkaline earth metal element, thereby achieving the intended purpose.

  According to the present invention, a first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum, a second catalyst containing an alkali metal element, and a third catalyst containing an alkaline earth metal element, Is supported on an inorganic oxide having heat resistance, so that the first catalyst becomes an oxide having a strong bond, and the second catalyst can be immobilized by adding the third catalyst. It is possible to obtain an effect that the catalyst metal scattering at the molecular level can be reduced.

Conceptual diagram of the exhaust gas purification device according to the second embodiment of the present invention Conceptual diagram of the evaluation method of the metal scattering test described in the examples of the present invention

  The exhaust gas purifying catalyst according to claim 1 of the present invention is a first catalyst containing at least one metal element selected from copper, vanadium or molybdenum, a second catalyst containing an alkali metal element, and an alkaline earth An exhaust gas purifying catalyst characterized in that a third catalyst containing a metal element is supported on an inorganic oxide having heat resistance.

  As a result, it is possible to obtain an exhaust gas purification catalyst that not only can efficiently oxidize and combust PM, but also can reduce catalyst metal scattering at the atomic or molecular level.

  Further, the exhaust gas purification catalyst shown here gives oxygen atoms contained in the catalyst to the PM to oxidize the PM, and the catalyst lacking oxygen atoms is easily oxidized by the oxygen in the exhaust gas and returns to its original state. PM can be continuously oxidized and burned by repeating the cycle.

  The first catalyst is an oxide containing at least one metal element selected from copper, vanadium, or molybdenum, so that it is oxidized by the release of oxygen atoms contained in the catalyst and oxygen in the exhaust gas. The cycle of returning to the above state can be repeated to promote the effect of the second catalyst continuously oxidizing and burning PM.

  Since the second catalyst contains an alkali metal element, it has a high combustion activity with respect to PM.

  When the third catalyst contains an alkaline earth metal element, it has an effect of fixing the second catalyst.

Moreover, copper takes bivalent and monovalent valences, and CuO (divalent) and Cu ₂ O (monovalent) exist as copper oxides, and atoms change when divalent to monovalent. Oxygen in between can be given to PM to oxidize. Since the copper oxide reduced to monovalent is easily oxidized by oxygen in the exhaust gas and returns to the divalent state, PM can be continuously oxidized and burned by this repetition.

In addition, vanadium takes many valences such as monovalent, divalent, trivalent, tetravalent, and pentavalent, and examples of vanadium oxide include V ₂ O (monovalent), V ₂ O ₂ (divalent), V ₂ O ₃ (trivalent), V ₂ O ₄ (tetravalent), V ₂ O ₅ (pentavalent) is present, and oxygen is changed by giving oxygen between atoms to PM when changing to a low valence. Can do. Since vanadium oxide reduced to a low valence is easily oxidized by oxygen in the exhaust gas, the repetition of this makes it possible to oxidize and burn PM continuously.

Molybdenum takes many valences such as divalent, trivalent, tetravalent, pentavalent, and hexavalent, and molybdenum oxides include MoO (divalent), Mo ₂ O ₃ (trivalent), and MoO _2. (Tetravalent), Mo ₂ O ₅ (pentavalent), and MoO ₃ (hexavalent) exist, and oxygen can be oxidized by giving oxygen between atoms to PM when changing to a low valence. Since molybdenum oxide reduced to a low valence is easily oxidized by oxygen in the exhaust gas, PM can be continuously oxidized and burned by this repetition.

  In addition, the composite oxide composed of at least two metal elements selected from copper, vanadium, or molybdenum has an action of enhancing the activity of the second catalyst, so that PM can be oxidized and burned efficiently. In addition, since the first catalyst becomes a complex oxide having a strong bond, metal atoms are fixed, and the first catalyst becomes an exhaust gas purifying catalyst in which scattering of the catalytic metal at the atomic or molecular level is reduced.

There are various complex oxides of copper and vanadium. In particular, the crystal structure of CuV ₂ O ₆ is very stable, so that oxygen between atoms can be stably given to PM to be oxidized. become.

  The catalyst carrier is preferably an inorganic oxide having heat resistance, and alumina, titania, silica, ceria, zirconia, or the like can be used. Since these have a large specific surface area, the surface area of the exhaust gas purification catalyst carried on the surface of the inorganic oxide can be increased and the contact probability with PM can be improved, so that PM can be oxidized and burned efficiently. In addition, since the heat resistance is high, the exhaust gas purification catalyst can be maintained in a stable state even when exposed to high temperature exhaust gas for a long time.

  The exhaust gas purification catalyst according to claim 2 of the present invention is an exhaust gas purification catalyst characterized in that the third catalyst contains a sulfate of an alkaline earth metal.

  Since the alkaline earth metal sulfate has an effect of immobilizing the alkali metal, particularly its sulfate, an exhaust gas purifying catalyst with reduced scattering of the catalytic metal at the atomic or molecular level can be obtained.

  The exhaust gas purifying catalyst according to claim 3 of the present invention is an exhaust gas purifying catalyst characterized in that the alkaline earth metal sulfate contains magnesium sulfate.

  Among alkaline earth metal sulfates, magnesium sulfate has an effect of fixing alkali metals, particularly sulfates thereof, so that it is possible to obtain an exhaust gas purification catalyst in which catalyst metal scattering at the atomic or molecular level is reduced. .

  According to a fourth aspect of the present invention, there is provided an exhaust gas purifying catalyst manufacturing method comprising: supporting a first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum on a heat-resistant inorganic oxide. An exhaust gas purification catalyst manufacturing method comprising: one step; and a second step of supporting a second catalyst containing an alkali metal element and a third catalyst containing an alkaline earth metal element.

  As a result, the first catalyst is supported on the surface of the heat-resistant inorganic oxide, and further, the second catalyst and the third catalyst are supported thereon, so that the PM can be oxidized and burned efficiently. In addition to being able to do so, it is possible to obtain an exhaust gas purification catalyst with reduced catalytic metal scattering at the atomic or molecular level.

  In the method for producing an exhaust gas purifying catalyst according to claim 5 of the present invention, a first solution containing at least one metal element selected from copper, vanadium, or molybdenum is impregnated with an inorganic oxide having heat resistance, After removing the surplus liquid, drying, then firing, the first step of supporting the first catalyst and the second solution containing the alkali metal element and the alkaline earth metal element were prepared in the first step. A method for producing an exhaust gas purifying catalyst, comprising: impregnating powder, removing excess liquid, drying, and then firing to carry a second catalyst and a third catalyst. It is.

  As a result, it is possible to produce an exhaust gas purification catalyst in which the first catalyst is supported on the surface of the heat-resistant inorganic oxide, and further the second catalyst and the third catalyst are supported thereon. This is a combination of a second catalyst having combustion activity and a first catalyst having an action of enhancing the activity of the second catalyst, and not only can PM be oxidized and burned efficiently, but also a third catalyst is added. As a result, the second catalyst can be immobilized, and thus an exhaust gas purification catalyst with reduced catalytic metal scattering at the atomic or molecular level can be obtained.

  Further, as the firing temperature of each step, the exhaust gas purification catalyst may be exposed to exhaust gas at about 600 ° C., and therefore it is preferable to fire at 600 ° C. or more during production, and further, if the catalyst is fired at a too high temperature, the catalyst Since the surface area of the catalyst becomes small and the catalytic activity decreases, it is preferable to calcine at 800 ° C. or lower.

  The exhaust gas purifying catalyst manufacturing method according to claim 6 of the present invention is the exhaust gas purifying catalyst manufacturing method, wherein the second solution contains an alkaline earth metal sulfate.

  Since the alkaline earth metal sulfate has an effect of immobilizing the alkali metal, particularly its sulfate, an exhaust gas purifying catalyst with reduced scattering of the catalytic metal at the atomic or molecular level can be obtained.

  According to a seventh aspect of the present invention, there is provided an exhaust gas purifying catalyst manufacturing method, wherein the alkaline earth metal sulfate contains magnesium sulfate.

  Among alkaline earth metal sulfates, magnesium sulfate has an effect of fixing alkali metals, particularly sulfates thereof, so that it is possible to obtain an exhaust gas purification catalyst in which catalyst metal scattering at the atomic or molecular level is reduced. .

  The exhaust gas purification filter according to claim 8 of the present invention is a first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum using an inorganic oxide having heat resistance as a catalyst carrier, an alkali An exhaust gas purification filter characterized in that an exhaust gas purification catalyst comprising a second catalyst containing a metal element and a third catalyst containing an alkaline earth metal element is supported on a three-dimensional structure.

  As a result, the first catalyst is supported on the surface of the heat-resistant inorganic oxide, and further, the second catalyst and the third catalyst are supported thereon, so that the PM can be oxidized and burned efficiently. In addition, it is possible to obtain an exhaust gas purification filter that reduces catalyst metal scattering at the atomic or molecular level.

  The three-dimensional structure shown here is not particularly limited as long as it has a three-dimensional structure and can adhere a liquid containing a catalyst or the like. However, PM can be oxidized efficiently. In order to burn, since it is necessary to increase the area for supporting the catalyst, it is preferable to use a honeycomb structure having a large surface area.

  Further, as the material of the three-dimensional structure, the exhaust gas temperature may exceed 600 ° C., so a heat-resistant ceramic, such as cordierite, alumina, silicon carbide, or a heat-resistant metal, for example, It is preferable to use stainless steel.

  Thereby, the heat resistance of the exhaust gas purification filter that will be exposed to the exhaust gas over a long period of time can be secured.

  The exhaust gas purification filter according to claim 9 of the present invention is an exhaust gas purification filter characterized in that the third catalyst contains a sulfate of an alkaline earth metal.

  Since the alkaline earth metal sulfate has an effect of immobilizing the alkali metal, particularly its sulfate, an exhaust gas purification filter with reduced catalyst metal scattering at the atomic or molecular level can be obtained.

  The exhaust gas purification filter according to claim 10 of the present invention is an exhaust gas purification filter characterized in that the alkaline earth metal sulfate contains magnesium sulfate.

  Among alkaline earth metal sulfates, magnesium sulfate has an effect of fixing alkali metals, particularly sulfates thereof, and therefore, it is possible to obtain an exhaust gas purification filter with reduced scattering of catalyst metal at the atomic or molecular level. .

  The method for producing an exhaust gas purification filter according to claim 11 of the present invention includes a first step of supporting a heat-resistant inorganic oxide on a three-dimensional structure, and at least one selected from copper, vanadium, or molybdenum. A second step of supporting a first catalyst containing a metal element; and a third step of supporting a second catalyst containing an alkali metal element and a third catalyst containing an alkaline earth metal element. This is an exhaust gas purification filter manufacturing method.

  Thereby, the inorganic oxide having heat resistance is supported on the surface of the three-dimensional structure, the first catalyst is supported on the surface of the inorganic oxide having heat resistance, and the second catalyst and the third catalyst are further supported thereon. Therefore, it is possible to obtain an exhaust gas purification filter in which not only PM can be oxidized and burned efficiently, but also catalyst metal scattering at the atomic or molecular level is reduced.

  In the exhaust gas purifying filter manufacturing method according to claim 12 of the present invention, a slurry containing an inorganic oxide having heat resistance is impregnated with a three-dimensional structure, and after removing excess liquid, drying and then firing. A first step of supporting an inorganic oxide having heat resistance, and an aqueous solution containing a copper element and a vanadium element are impregnated with the three-dimensional structure obtained in the first step, and after removing excess liquid, drying is performed. Then, the second step of supporting the first catalyst by calcination and the aqueous solution containing the cesium element and the magnesium element were impregnated with the three-dimensional structure obtained in the second step, and the excess liquid was removed. And a third step of supporting the second catalyst and the third catalyst by drying and then calcining.

  As a result, an inorganic oxide having heat resistance is supported on the surface of the three-dimensional structure, and a composite oxide of copper and vanadium is supported on the surface of the inorganic oxide having heat resistance, and further to the cesium element and magnesium Since it becomes an exhaust gas purification filter carrying a compound containing an element, not only PM can be oxidized and burned efficiently, but also an exhaust gas purification filter with reduced catalyst metal scattering at the atomic or molecular level is obtained. be able to.

  Further, as the firing temperature in each step, the exhaust gas purification filter may be exposed to exhaust gas at about 600 ° C., and therefore, it is preferable to fire at 600 ° C. or higher during production, and further, if it is fired at a too high temperature, the catalyst Since the surface area of the catalyst becomes small and the catalytic activity decreases, it is preferable to calcine at 800 ° C. or lower.

  The exhaust gas purifying apparatus according to claim 13 of the present invention is an exhaust gas purifying apparatus characterized in that the exhaust gas purifying filter is arranged.

  The exhaust gas purification filter uses a heat-resistant inorganic oxide as a catalyst carrier, a first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum, and a second catalyst containing an alkali metal element. And a third catalyst containing an alkaline earth metal element, an exhaust gas purification filter comprising an exhaust gas purification catalyst supported on a three-dimensional structure, so that PM can be oxidized and burned efficiently. In addition to this, it is possible to obtain an exhaust gas purifying apparatus in which catalytic metal scattering at the atomic or molecular level is reduced.

  The exhaust gas purifying apparatus according to claim 14 of the present invention is an exhaust gas purifying apparatus characterized in that the three-dimensional structure is a diesel particulate filter.

  Since a diesel particulate filter (hereinafter referred to as DPF) has excellent PM collection efficiency, even PM having a small particle diameter contained in the exhaust gas can be collected and the exhaust gas can be purified.

  Further, since DPF has a very large surface area, the amount of catalyst supported can be increased, and PM can be oxidized and burned efficiently.

  The exhaust gas purifying apparatus according to claim 15 of the present invention is an exhaust gas purifying apparatus characterized in that the material of the three-dimensional structure is a heat-resistant ceramic or a heat-resistant metal.

  Thereby, the heat resistance of the exhaust gas purification filter that will be exposed to the exhaust gas over a long period of time can be secured.

  Moreover, since the exhaust gas temperature may exceed 600 ° C., it is preferable to use stainless steel as the heat-resistant metal such as cordierite, alumina, silicon carbide, etc. as the heat-resistant ceramic.

  The exhaust gas purifying apparatus according to claim 16 of the present invention is an exhaust gas purifying apparatus characterized by further disposing an exhaust gas oxidation filter having a noble metal element.

By disposing an exhaust gas oxidation filter having a noble metal element, carbon monoxide (hereinafter referred to as CO) or hydrocarbons (hereinafter referred to as HC) contained in the exhaust gas is converted into carbon dioxide (hereinafter referred to as CO ₂ ). Nitric oxide (hereinafter referred to as NO) can be oxidized to nitrogen dioxide (hereinafter referred to as NO ₂ ).

  The exhaust gas purifying apparatus according to claim 17 of the present invention is an exhaust gas purifying apparatus characterized in that an exhaust gas oxidation filter is disposed in front of the exhaust gas purification filter.

  The exhaust gas oxidation filter oxidizes carbon monoxide, hydrocarbons, etc. contained in the exhaust gas into carbon dioxide, generating oxidation heat, and the exhaust gas temperature flowing into the exhaust gas purification filter in the subsequent stage rises. There is an effect that the accumulated PM is more easily combusted.

Further, NO ₂ produced by the action of the exhaust gas oxidation filter has a high oxidizing power with respect to PM, an effect that PM accumulated in the exhaust gas purification filter is easier to burn.

  The exhaust gas purifying apparatus according to claim 18 of the present invention is an exhaust gas purifying apparatus characterized in that the exhaust gas oxidation filter has a flow-through honeycomb structure.

Since the honeycomb structure has a very large surface area, the amount of catalyst supported can be increased, so CO and HC in the exhaust gas passing through the filter are efficiently oxidized to CO ₂ and NO to NO ₂ efficiently. can do.

  Also, since PM in the exhaust gas is collected by the exhaust gas purification filter at the subsequent stage and is oxidized and burned by the action of the exhaust gas purification catalyst, the exhaust gas oxidation filter at the front stage uses a flow-through honeycomb structure with low PM collection efficiency. Is preferred.

  The exhaust gas purifying apparatus according to claim 19 of the present invention is an exhaust gas purifying apparatus characterized in that the material of the exhaust gas oxidation filter is a heat-resistant ceramic or a heat-resistant metal.

  Thereby, the heat resistance of the exhaust gas oxidation filter that will be exposed to the exhaust gas over a long period of time can be secured.

  Moreover, since the exhaust gas temperature may exceed 600 ° C., it is preferable to use stainless steel as the heat-resistant metal such as cordierite, alumina, silicon carbide, etc. as the heat-resistant ceramic.

  The exhaust gas purification apparatus according to claim 20 of the present invention is an exhaust gas purification apparatus characterized in that the noble metal element contains at least one element selected from platinum, palladium, and rhodium.

  Thereby, gas components, such as HC, CO, NO, in exhaust gas can be oxidized efficiently.

  Further, the noble metal element is preferably a carrier made of an inorganic oxide having heat resistance such as alumina, titania, silica, ceria, or zirconia. By supporting the noble metal on alumina or the like, it is possible to obtain the effects of suppressing the deterioration of the noble metal and supporting the noble metal in a highly dispersed state.

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

(Embodiment 1)
The exhaust gas purification filter and the manufacturing method thereof according to the present invention will be described.

Titania manufactured by impregnating cordierite DPF as a three-dimensional structure into a first liquid in which titania as an inorganic oxide having heat resistance is dispersed, removing excess liquid, drying, and then firing. A supported cordierite (hereinafter referred to as TiO ₂ / Cd) is impregnated in a second liquid containing copper sulfate pentahydrate and vanadium oxide n-hydrate, after removing the excess liquid, drying and then firing. Thus, the first catalyst mainly composed of CuV ₂ O ₆ was supported on the TiO ₂ / Cd surface (hereinafter referred to as CuV / TiO ₂ / Cd). Next, the third liquid containing cesium sulfate and magnesium sulfate is impregnated with CuV / TiO ₂ / Cd, the excess liquid is removed, dried, and then fired, whereby the surface of the CuV / TiO ₂ / Cd is cesium sulfate. And a third catalyst containing magnesium sulfate were supported (hereinafter referred to as CsMg / CuV / TiO ₂ / Cd).

CsMg / CuV / TiO ₂ / Cd prepared by the above-described method uses titania having a large specific surface area as a catalyst carrier, so that the surface area of the exhaust gas purification catalyst is increased and the contact probability with PM is improved. In addition to being able to oxidize and burn well, since titania has high heat resistance, it can maintain a stable state even when exposed to high-temperature exhaust gas for a long time.

  Moreover, since CuV which is a 1st catalyst has the effect | action which raises the activity of CsMg which is a 2nd catalyst, it can oxidize and burn PM efficiently.

  Further, since cesium sulfate is supported as the second catalyst, PM can be oxidized and burned efficiently.

  Moreover, since the magnesium sulfate which has an effect which fix | immobilizes a cesium sulfate is carry | supported as a 3rd catalyst, the amount of scattering of a cesium sulfate can be reduced.

(Embodiment 2)
The exhaust gas purification apparatus according to the present invention will be described with reference to FIG.

  As shown in FIG. 1, the exhaust gas purifying apparatus according to the present invention includes a silicon carbide exhaust gas purifying filter 2 in which an exhaust gas purifying catalyst is supported in a filter case 1, and a flow in front of the exhaust gas purifying filter 2. An exhaust gas oxidation filter 3 made of platinum-supporting cordierite having a through honeycomb structure is provided.

  PM4 in the exhaust gas discharged from the diesel engine is collected by the exhaust gas purification filter 2, and simultaneously contacts the exhaust gas purification catalyst carried on the exhaust gas purification filter 2. PM4 collected and brought into contact with the exhaust gas purification catalyst is oxidized and discharged as carbon dioxide. By performing this collection and combustion as needed, the exhaust gas purification filter 2 can continuously purify the exhaust gas without being clogged with the accumulation of PM4.

  At this time, the exhaust gas purification filter 2 is an exhaust gas purification filter in which a composite oxide of copper and vanadium is supported on the surface of an inorganic oxide having heat resistance, and further a compound containing a cesium element and a magnesium element is supported thereon. Therefore, it is possible not only to oxidize and burn PM efficiently, but also to obtain a filter with reduced catalytic metal scattering at the atomic or molecular level.

Further, an exhaust gas oxidation filter 3 made of platinum-carrying cordierite is disposed in front of the exhaust gas purification filter 2, so that the exhaust gas oxidation filter 3 oxidizes CO, HC, etc. contained in the exhaust gas into CO ₂ to generate oxidation heat. Is generated, and the temperature of the exhaust gas flowing into the exhaust gas purification filter at the subsequent stage rises, so that PM deposited on the exhaust gas purification filter becomes more easily combusted.

Furthermore, since NO ₂ generated by the action of the exhaust gas oxidation filter 3 has a high oxidizing power with respect to PM, the PM deposited on the exhaust gas purification filter becomes more easily combusted.

  Examples of the present invention will be described below.

  The exhaust gas purification filter and the manufacturing method thereof according to the present invention will be described.

Titania manufactured by impregnating a cordierite honeycomb as a three-dimensional structure into a first liquid in which titania as a heat-resistant inorganic oxide is dispersed, removing excess liquid, drying, and then firing. The supported cordierite (hereinafter referred to as TiO ₂ / Cd) is impregnated in a second liquid (Cu: V = 1: 2) containing copper sulfate pentahydrate and vanadium oxide sulfate n hydrate to remove excess liquid. Then, the first catalyst mainly composed of CuV ₂ O ₆ was supported on the surface of TiO ₂ / Cd by drying and then firing at 800 ° C. (hereinafter referred to as CuV / TiO ₂ / Cd). The generation of _CuV 2 _{O 6} was confirmed by X-ray diffractometer (XRD). Next, after impregnating CuV / TiO ₂ / Cd into a third liquid (Cs: Mg = 1: 1, 1: 0.5, or 1: 0) containing cesium sulfate and magnesium sulfate, and removing the excess liquid, The second catalyst containing cesium sulfate and the third catalyst containing magnesium sulfate were supported on the CuV / TiO ₂ / Cd surface by drying and then firing at 700 ° C. (hereinafter referred to as CsMg / CuV / TiO ₂ / Cd). ). The presence of cesium sulfate and magnesium sulfate was confirmed by XRD.

CsMg / CuV / TiO ₂ / Cd prepared by the above-described method uses titania having a large specific surface area as a catalyst carrier, so that the surface area of the exhaust gas purification catalyst is increased and the contact probability with PM is improved. In addition to being able to oxidize and burn well, since titania has high heat resistance, it can maintain a stable state even when exposed to high-temperature exhaust gas for a long time.

The first catalyst has become substantially in the form of CuV ₂ O _6, since CuV ₂ O ₆ is with a strong bond not only can reduce the catalytic metal diffusing in atomic or molecular level, a second Since it has the effect | action which raises the activity of a catalyst, PM can be oxidatively burned efficiently.

  Moreover, since the cesium sulfate which shows the highest combustion activity with respect to PM is carry | supported as a 2nd catalyst among sulfates of alkali metal, PM can be oxidatively burned efficiently.

  Moreover, since magnesium sulfate which has an effect of fixing an alkali metal sulfate is supported as the third catalyst, the amount of cesium sulfate scattered can be reduced.

(Comparative example)
Titania manufactured by impregnating a cordierite honeycomb as a three-dimensional structure into a first liquid in which titania as a heat-resistant inorganic oxide is dispersed, removing excess liquid, drying, and then firing. A supported cordierite (hereinafter referred to as TiO ₂ / Cd) is added to a solution (Cs: Cu: V = 0.75: 1: 2) containing cesium sulfate, copper sulfate pentahydrate and vanadium oxide sulfate n hydrate. After the impregnation, drying and then baking at 800 ° C. supported a composite oxide composed of cesium, copper and vanadium on the surface of TiO ₂ / Cd (hereinafter referred to as CsCuV / TiO ₂ / Cd).

(Evaluation example 1)
Next, a metal scattering test of the exhaust gas purification filter according to the present invention was performed. A conceptual diagram of the evaluation method is shown in FIG.

The honeycomb-shaped CsMg / CuV / TiO ₂ / Cd produced by the method described in the examples was cut to a diameter of 20 mm and a length of 20 mm to form an exhaust gas purification filter sample 5 and placed in a glass tube 6 having an inner diameter of 20 mm. Then, about 0.4 g of quartz wool 7 was packed behind the exhaust gas purification filter sample 5 and set in the heating tubular furnace 8 so that the exhaust gas purification filter sample 5 was at the center. A thermocouple 9 was inserted into a cell near the center of the exhaust gas purification filter sample 5 so that the surface temperature of the exhaust gas purification filter sample 5 could be measured, and then the surface of the exhaust gas purification filter sample 5 was heated to 600 ° C.

Next, a mixed gas was prepared so that carbon monoxide 150 ppm, propylene 50 ppm, nitrogen monoxide 500 ppm, sulfur dioxide 1 ppm, oxygen 8 vol%, carbon dioxide 8 vol%, and moisture 10 vol%. ^-Gas was circulated for 14 hours.

Next, the quartz wool 7 after the gas flow operation for 14 hours is taken out, components adhering to the quartz wool 7 are dissolved in aqua regia, and the metal ion concentration in the solution is determined by inductively coupled plasma mass spectrometry (ICP-MS). The metal scattering amount (μg / m ³ ) was calculated therefrom. The results are shown in Table 1.

From the results of Table 1, the scattering amount of vanadium was 49 to 31 μg / m ³ and was reduced by about 40%, and the scattering amount of cesium was 230 to 61 μg / m ³ and was reduced by about 75%.

  This reduction in the amount of scattered cesium is due to the effect of magnesium sulfate, and as the third catalyst, magnesium sulfate, which has the effect of immobilizing alkali metal sulfates, was supported, and in particular, the amount of scattered cesium sulfate could be reduced. Conceivable.

(Evaluation example 2)
Next, the carbon combustion activity test of the exhaust gas purification filter according to the present invention was performed. The test method will be described.

A differential thermothermal gravimetric simultaneous measurement apparatus (TG-) was prepared by pulverizing and mixing 0.04 g of CsMg / CuV / TiO ₂ / Cd and 0.01 g of carbon black in a mortar for 1 hour. DTA) was used to measure the change in weight when the temperature was raised at 5 ° C./min. The carbon combustion activity was evaluated by comparing the temperature when the weight was reduced by 10% with the weight at 200 ° C. being 100%. The results are shown in Table 2.

  From the results of Table 2, it was found that there was almost no difference in carbon combustion activity when the Mg / Cs ratio was in the range of 0 to 1, and it was found that all had high carbon combustion activity.

  The exhaust gas purifying catalyst according to the present invention includes a first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum, a second catalyst containing an alkali metal element, and a second catalyst containing an alkaline earth metal element. By making an exhaust gas purification catalyst characterized by supporting three catalysts with a heat-resistant inorganic oxide, not only can PM be oxidized and burned efficiently, but also at the atomic or molecular level. It is useful as an exhaust gas purification catalyst that can reduce the metal scattering of the catalyst.

1 Filter case 2 Exhaust gas purification filter 3 Exhaust gas oxidation filter 4 PM
5 Exhaust gas purification filter sample 6 Glass tube 7 Quartz wool 8 Heated tubular furnace 9 Thermocouple

Claims (20)

A first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum, a second catalyst containing an alkali metal element, and a third catalyst containing an alkaline earth metal element have heat resistance. An exhaust gas purification catalyst which is supported on an inorganic oxide. The exhaust gas purifying catalyst according to claim 1, wherein the third catalyst contains an alkaline earth metal sulfate. The exhaust gas purifying catalyst according to claim 2, wherein the alkaline earth metal sulfate contains magnesium sulfate. A first step of supporting a first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum on a heat-resistant inorganic oxide; a second catalyst containing an alkali metal element; and an alkaline earth A method for producing an exhaust gas purifying catalyst, comprising: a second step of supporting a third catalyst containing a metal element. A first solution containing at least one metal element selected from copper, vanadium, or molybdenum is impregnated with a heat-resistant inorganic oxide, the excess liquid is removed, dried, and then fired. 1 The first step of supporting the catalyst, and the second solution containing the alkali metal element and the alkaline earth metal element are impregnated with the powder prepared in the first step, the excess liquid is removed, and then dried. The method for producing an exhaust gas purification catalyst according to claim 4, comprising: a second step of supporting the second catalyst and the third catalyst by firing. 6. The method for producing an exhaust gas purification catalyst according to claim 5, wherein the second solution contains an alkaline earth metal sulfate. The method for producing an exhaust gas purification catalyst according to claim 6, wherein the alkaline earth metal sulfate contains magnesium sulfate. A first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum, a second catalyst containing an alkali metal element, and an alkaline earth metal element using an inorganic oxide having heat resistance as a catalyst carrier An exhaust gas purifying filter comprising an exhaust gas purifying catalyst comprising a third catalyst and a three-dimensional structure. The exhaust gas purification filter according to claim 8, wherein the third catalyst contains a sulfate of an alkaline earth metal. The exhaust gas purification filter according to claim 8 or 9, wherein the alkaline earth metal sulfate contains magnesium sulfate. A first step of supporting a heat-resistant inorganic oxide on a three-dimensional structure; a second step of supporting a first catalyst containing at least one metal element selected from copper, vanadium, or molybdenum; and an alkali A method for producing an exhaust gas purification filter, comprising: a third step of supporting a second catalyst containing a metal element and a third catalyst containing an alkaline earth metal element. A first step of supporting a heat-resistant inorganic oxide by impregnating a slurry containing a heat-resistant inorganic oxide with a three-dimensional structure, removing excess liquid, drying, and then firing; and copper A second step of supporting the first catalyst by impregnating the aqueous solution containing the element and vanadium element with the three-dimensional structure obtained in the first step, removing excess liquid, drying, and then firing. And an aqueous solution containing a cesium element and a magnesium element are impregnated with the three-dimensional structure obtained in the second step, the excess liquid is removed, dried, and then calcined. The method for producing an exhaust gas purification filter according to claim 11, comprising a third step of supporting a catalyst. An exhaust gas purification apparatus comprising the exhaust gas purification filter according to any one of claims 8 to 10. The exhaust gas purification apparatus according to claim 13, wherein the three-dimensional structure is a diesel particulate filter. The exhaust gas purifying apparatus according to claim 13 or 14, wherein the material of the three-dimensional structure is ceramic having heat resistance or metal having heat resistance. The exhaust gas purification device according to any one of claims 13 to 15, further comprising an exhaust gas oxidation filter having a noble metal element. The exhaust gas purification device according to any one of claims 13 to 16, wherein the exhaust gas oxidation filter is disposed in front of the exhaust gas purification filter. The exhaust gas purification apparatus according to claim 16 or 17, wherein the exhaust gas oxidation filter has a flow-through honeycomb structure. The exhaust gas purifying apparatus according to any one of claims 16 to 18, wherein a material of the exhaust gas oxidation filter is ceramic having heat resistance or metal having heat resistance. The exhaust gas purifying apparatus according to any one of claims 16 to 19, wherein the noble metal element includes at least one element selected from platinum, palladium, and rhodium.

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