JP2006198490A - Exhaust gas cleaning catalyst, its manufacturing method and exhaust gas cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas cleaning catalyst capable of efficiently performing the decomposition treatment of nitrogen oxide over the whole temperature range of the exhaust gas discharged from a diesel engine or the like, its manufacturing method and an exhaust gas cleaning method. <P>SOLUTION: A solution, in which metal components are dissolved, is added to a precursor 111a in an amorphous state of a carrier 111 comprising an oxide to hold a plurality of the metal components 112a and 112b on the precursor 111a and this precursor 111a is heat-treated in a non-oxidizing atmosphere such as a nitrogen gas or the like and changed structurally to obtain the exhaust gas cleaning catalyst wherein alloy particles with a particle size of 100 nm or below composed of a solid solution of a plurality of the metal components 112a and 112b are supported on the carrier 111 comprising the oxide. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purifying catalyst for decomposing nitrogen oxides in exhaust gas discharged from a diesel engine or the like, a method for producing an exhaust gas purifying catalyst, and an exhaust gas purifying method.

  As an exhaust gas purifying catalyst for decomposing nitrogen oxides in exhaust gas discharged from a diesel engine, etc., metal particles such as Pt, Pd, Au, Rh, Ag, Ir, etc. on a carrier made of a metal oxide such as titanium oxide. Are used alone or in combination.

  As such an exhaust gas purifying catalyst, for example, after the metal particles are attached to the carrier, the surface of the metal particles is coated so that a part of the surface of the metal particles is coated with a different type of metal phase from the metal particles. In this regard, a product obtained by reducing and precipitating is known (for example, see Patent Documents 1 and 2 below).

JP-A-11-156193 JP-A-11-347424

  By the way, the temperature of exhaust gas discharged from a diesel engine or the like varies widely depending on the load condition of the diesel engine or the like (about 250 to 450 ° C.). For this reason, an exhaust gas purifying catalyst that decomposes nitrogen oxides in exhaust gas discharged from a diesel engine or the like is strongly required to be able to act efficiently over the entire temperature range of the exhaust gas discharged from the diesel engine or the like. However, in the exhaust gas purifying catalyst described in Patent Documents 1 and 2 and the like as described above, the decomposition treatment of nitrogen oxides could not be efficiently expressed over the wide temperature range as described above. .

  Therefore, the present invention uses an exhaust gas purifying catalyst capable of efficiently expressing the decomposition treatment of nitrogen oxide over the entire temperature range of exhaust gas discharged from a diesel engine or the like, a method for producing the same, and a catalyst using the catalyst. An object of the present invention is to provide a method for purifying exhaust gas.

  An exhaust gas purifying catalyst according to the present invention for solving the above-mentioned problems comprises a support made of an oxide, and alloy particles supported on the support and having a plurality of metal components dissolved therein, The particle size is 100 nm or less.

In the exhaust gas purifying catalyst according to the present invention, the carrier is a composite of at least two of TiO ₂ , SiO ₂ , Al ₂ O ₃ , ZrO ₂ , CaO, MgO, SnO ₂ and ZnO. It consists of an oxide.

  The exhaust gas purifying catalyst according to the present invention is characterized in that, in the above, the alloy particles are solid solutions of at least two kinds of Pt, Ir, Pd, Rh, Ru, Au, and Ag.

  The exhaust gas purifying catalyst according to the present invention is characterized in that, in the above, the alloy particles are solid solutions of at least two kinds of metal components containing Ir and have a particle size of 10 nm or more. .

  The exhaust gas purifying catalyst according to the present invention is characterized in that, in the above, the alloy particles are supported at a ratio of 0.1 to 5 wt% with respect to the carrier.

  On the other hand, the method for producing an exhaust gas purifying catalyst according to the present invention is the above-described method for producing an exhaust gas purifying catalyst according to the present invention, wherein a metal component is dissolved in an amorphous precursor of the carrier made of an oxide. The precursor is made to contain a plurality of metal components in the precursor, and then the precursor is heat-treated in a non-oxidizing atmosphere to change the structure. The alloy particles in which the metal component is dissolved are supported.

  In the above-described method for producing an exhaust gas purifying catalyst according to the present invention, the non-oxidizing atmosphere includes at least one of a reducing gas and an inert gas.

  In the above-described method for producing an exhaust gas purifying catalyst according to the present invention, the non-oxidizing atmosphere contains water vapor.

  Furthermore, the exhaust gas purification method according to the present invention is characterized in that the exhaust gas purification catalyst according to the present invention and the exhaust gas are brought into contact with each other to decompose nitrogen oxides in the exhaust gas.

  The exhaust gas purification method according to the present invention is characterized in that, in the above, the exhaust gas is a gas having a temperature of 250 to 450 ° C. discharged from a diesel engine.

  According to the exhaust gas purifying catalyst of the present invention, since the carrier supports alloy particles having a particle size of 100 nm or less and in which a plurality of metal components are solid-solved, nitrogen oxides over a wide temperature range of 250 to 450 ° C. Can be efficiently performed.

  Moreover, according to the method for producing an exhaust gas purifying catalyst according to the present invention, the exhaust gas purifying catalyst according to the present invention can be easily produced.

  In addition, according to the exhaust gas purification method of the present invention, nitrogen oxides can be efficiently decomposed over the entire temperature range of the exhaust gas, even if the exhaust gas is from a diesel engine whose temperature varies widely depending on the load condition. it can.

  An embodiment of an exhaust gas purifying catalyst, an exhaust gas purifying catalyst manufacturing method and an exhaust gas purifying method according to the present invention will be described with reference to FIGS. FIG. 1 is a flowchart showing the procedure of a method for producing an exhaust gas purification catalyst, and FIG. 2 is an explanatory diagram of the method for producing an exhaust gas purification catalyst.

  The exhaust gas purifying catalyst according to the present embodiment includes a support made of an oxide, and alloy particles supported on the support and having a plurality of metal components dissolved therein, and the alloy particles have a particle size of 100 nm or less (more preferably 50 nm or less).

  Here, if the particle size of the alloy particles exceeds 100 nm, the surface area for the increase in the weight of the alloy particles becomes too small, and a sufficient catalytic function is exhibited in decomposing nitrogen oxides in the flowing exhaust gas. Cannot be applied.

The carrier is preferably composed of a composite oxide of at least two of TiO ₂ , SiO ₂ , Al ₂ O ₃ , ZrO ₂ , CaO, MgO, SnO ₂ and ZnO. It is preferable to combine the above two types so that one is in the range of 5 to 95 mol% and the other is in the remaining ratio because a stable composite oxide can be obtained.

Further, a combination of TiO ₂ and ZrO ₂ (especially in the case of a ratio of 45 to 55 mol%: 45 to 55 mol%), a combination of TiO ₂ and SiO ₂ (especially 85 to 95 mol%: 5 to 15 mol%). In the case of the ratio), the increase in the acid point due to the combination becomes very large, and the denitration performance can be greatly improved, which is very preferable.

  The alloy particles are preferably a solid solution of at least two of Pt, Ir, Pd, Rh, Ru, Au, and Ag. In particular, two of the metal components are combined and one of them is combined. It is preferable that the content is 20 to 80 wt% and the other is the remaining ratio because stable alloy particles can be obtained.

  Further, the alloy particles may be a solid solution of two kinds of metal components containing at least Ir, for example, a combination of Ir and Pt (especially in the case of 50 to 80 wt%: 20 to 50 wt%), Ir and Rh, The combination (particularly in the case of 50 to 80 wt%: 20 to 50 wt%) is very preferable because the denitration performance at a high temperature of 350 ° C. or higher can be greatly improved. In the case of alloy particles containing Ir, it is very preferable that the particle size of the alloy particles is 10 nm or more because the catalytic activity is particularly high.

  The alloy particles are preferably supported at a rate of 0.1 to 5 wt% with respect to the support, and particularly preferably at a rate of 1 to 3 wt%. This is because if the amount of the alloy particles supported on the support is less than 0.1 wt%, it is difficult to fully exhibit the function as a catalyst, and if it exceeds 5 wt%, the particle size of the alloy particles during catalyst preparation This is because the possibility of exceeding 100 nm becomes very high.

  As shown in FIGS. 1 and 2, the manufacturing method of the exhaust gas purifying catalyst according to the present embodiment produces an amorphous precursor 111a of a carrier made of an oxide (S1 in FIG. 1, FIG. 2). (A)) A solution in which a plurality of metal components 112a and 112b are dissolved is impregnated in the precursor 111a and dried to hold the plurality of metal components 112a and 112b (particle size of 1 nm or less) in the precursor 111a. (S2 in FIG. 1, (b) in FIG. 2), the precursor 111a is heat-treated in a non-oxidizing atmosphere to change the structure (S3 in FIG. 1), thereby forming the oxide carrier 111. Further, it is possible to easily obtain the exhaust gas purifying catalyst 110 supporting the alloy particles 112 (particle size of 100 nm or less) in which the plurality of metal components 112a and 112b are solid-solved ((c) in FIG. 2).

Here, examples of the raw material of the carrier (precursor raw material) include various chlorides, nitrates, sulfates, and the like. Specifically, for example, in the case of TiO ₂ , TiCl ₄ , TiOSO _{3 and the} like are mentioned, in the case of SiO ₂ , water glass, silica sol and the like are mentioned, and in the case of Al ₂ O ₃ , AlCl ₃ is mentioned. _In the case of ZrO ₂ , ZrOCl _{2 and the} like are mentioned. In the case of CaO, CaCl ₂ and Ca (NO ₃ ) ₂ are mentioned, and in the case of MgO, MgCl ₂ and Mg (NO ₃ ) _{2 and the} like are mentioned. In the case of SnO ₂ , SnCl _{2 and the} like are mentioned, and in the case of ZnO, ZnCl _{2 and the} like are mentioned.

  By mixing and dissolving these raw materials in water at a predetermined ratio, adding ammonia water or the like and stirring, precipitates (amorphous precursor of the carrier) presumed to be composite hydroxides of these raw materials are generated, The precursor in the amorphous state of the carrier can be obtained by solid-liquid separation and drying the solid content.

Moreover, as a raw material of the said metal component, various chlorides, nitrate, ammonium salt etc. are mentioned, for example. Specifically, for example, in the case of Pt, H ₂ PtCl ₆ , Pt (NH ₃ ) ₄ (OH) _{2 and the} like can be mentioned, and in the case of Ir, H ₂ IrCl ₆ , Ir (NH ₃ ) ₆ Cl _{3 and the} like are mentioned. In the case of Pd, H ₂ PdCl ₄ , Pd (NH ₃ ) ₂ (NO ₂ ) ₂ aq, Pd (NO ₃ ) and the like are mentioned. In the case of Rh, H ₂ RhCl ₆ , Rh (NO ₃ ) _{3 and the} like. In the case of Ru, H ₂ RuCl ₅ , Ru (NO ₃ ) _{3 and the} like are mentioned. In the case of Au, HAuCl ₄ aq and the like are mentioned. In this case, AgNO _{3 and the} like can be mentioned.

  These raw materials are mixed and dissolved in water at a predetermined ratio, the precursor is impregnated with the aqueous solution, and the precursor is dried, whereby the precursor is held in the precursor, and this is subjected to heat treatment (pre-heat treatment). By doing, each metal component (particle size of 1 nm or less) can be easily held in the precursor.

  The non-oxidizing atmosphere is a gas atmosphere that does not contain oxygen gas. For example, a reducing gas such as hydrogen gas, an inert gas such as nitrogen gas, helium gas, or argon gas, or these reducing gases. Examples thereof include a mixed gas of a gas and an inert gas, and those obtained by adding water vapor to these gases.

  In the exhaust gas purifying catalyst according to this embodiment manufactured as described above, the nitrogen oxide in the exhaust gas can be decomposed by contacting with the exhaust gas discharged from a diesel engine or the like.

  At this time, although the exhaust gas discharged from the diesel engine or the like varies widely in temperature depending on the load condition of the diesel engine or the like (about 250 to 450 ° C.), in the exhaust gas purifying catalyst according to the present embodiment, the temperature of the exhaust gas. Nitrogen oxide can be efficiently decomposed over the entire region (about 250 to 450 ° C.). The reason for this will be described below.

  The metal component exhibiting catalytic activity differs in temperature at which activity is manifested for each element type. In such alloy particles in which a plurality of types of metal components having different activity expression temperatures are solidified, these metal components are mixed together to have different crystal structures, and therefore differ from the activity expression temperature of each element of the composition component. Although the activity was expressed at the temperature, it was considered that the temperature range of the activity expression hardly changed.

  However, when the inventors of the present application have conducted intensive research, in alloy particles in which a plurality of types of metal components having different activity expression temperatures are solid-solubilized, a temperature different from the activity expression temperature of each element of the composition component of the alloy particles. In addition to expressing the activity, it was possible to obtain the knowledge that the temperature range of the activity expression markedly increased.

  Therefore, the catalyst in which the alloy component whose activity expression temperature range is remarkably increased is supported on the carrier is used for the decomposition treatment of nitrogen oxide in the gas whose temperature fluctuates widely such as exhaust gas discharged from a diesel engine or the like. By using it, it becomes possible to efficiently decompose nitrogen oxides over the entire temperature range (about 250 to 450 ° C.) of the exhaust gas.

  By the way, in a catalyst that decomposes nitrogen oxides or the like in exhaust gas discharged from a diesel engine or the like, nitrogen oxides must be decomposed by efficiently contacting with exhaust gas flowing and discharged at a relatively high speed. Therefore, the alloy particles need to have a very large surface area, that is, a very small particle size, specifically, 100 nm or less.

  However, it is very difficult to produce alloy particles having a very small particle size of 100 nm or less, and even if alloy particles having a particle size of 100 nm or less are produced, the carrier is not aggregated. It becomes extremely difficult to carry the film uniformly.

  Therefore, as a result of further diligent research conducted by the inventors of the present application, first, an amorphous precursor of a support made of an oxide is prepared, and a solution in which a metal component is dissolved is contained in the precursor to thereby add a plurality of metal components. Then, when the precursor is heat-treated in a non-oxidizing atmosphere to change the structure, a plurality of alloy particles having a particle size of 100 nm or less in which a plurality of the metal components are dissolved are supported on the oxide support. It has been found that an exhaust gas purifying catalyst can be easily obtained.

  The reason why an exhaust gas-purifying catalyst in which an alloy particle having a particle diameter of 100 nm or less in which a plurality of metal components are dissolved in a carrier made of an oxide is easily obtained by such a manufacturing method is not clear. By containing a solution in which a component is dissolved in the precursor, a minute metal component (1 nm or less) is retained in the precursor, and when the precursor is heat-treated to change the structure, the molecular structure of the precursor is changed. It is inferred that (with crystallization), the metal component moves and becomes compatible with the metal component located in the vicinity, resulting in alloy particles having an appropriate particle size (100 nm or less). .

  Moreover, when the heat treatment is performed in an oxidizing atmosphere (an atmosphere containing oxygen gas), alloy particles are not generated, and only metal components particles in which each metal component is grown are generated. Although the reason for this is not clear, when the heat treatment is performed in an oxidizing atmosphere (an atmosphere containing oxygen gas), an oxide film is formed on the surface of each metal component, and compatibility between different types of metal components is increased. It is speculated that it may be significantly reduced.

  Therefore, according to the exhaust gas purifying catalyst according to the present embodiment, it is possible to efficiently perform the decomposition treatment of nitrogen oxide over the wide temperature range of 250 to 450 ° C., and manufacture of the exhaust gas purifying catalyst according to the present embodiment. According to the method, the exhaust gas purifying catalyst according to the present embodiment can be easily manufactured. According to the exhaust gas purifying method according to the present embodiment, exhaust gas from a diesel engine or the like whose temperature varies widely depending on the load condition. Even if it exists, a nitrogen oxide can be efficiently decomposed | disassembled over the whole temperature range of the said waste gas.

  In order to confirm the effects of the exhaust gas purifying catalyst, the exhaust gas purifying catalyst manufacturing method and the exhaust gas purifying method according to the present invention, the following experiments were conducted.

[A. Production of catalyst]
<Test body 1>
A TiCl ₄ aqueous solution and a ZrOCl ₂ aqueous solution are mixed so that the molar ratio of Ti and Zr is 50:50, an aqueous ammonia solution is added and stirred, and the resulting precipitate is filtered and dried (120 ° C. × 2 hours) ) To produce an amorphous precursor (TiO ₂ —ZrO ₂ hydroxide) of an oxide carrier.

Subsequently, the precursor is impregnated with an aqueous solution in which H ₂ IrCl ₆ and H ₂ PtCl ₆ are mixed and dissolved at a ratio of 1 wt% Ir and 0.5 wt% Pt with respect to the weight of the support and dried ( 100 ° C. × 24 hours), Ir and Pt are held in the precursor.

Next, the precursor is pre-heated in an air atmosphere (500 ° C. × 5 hours) to first remove corrosive components such as chlorine in various remaining raw materials, and then the precursor is non-oxidized. By performing heat treatment (750 ° C. × 6 hours) in an atmosphere (nitrogen gas containing 10% H ₂ O), the precursor is structurally changed to be crystallized, and an exhaust gas purifying catalyst specimen 1 (particle size) 0.5-1 mm).

<Specimen 2>
In the manufacturing method of the test body 1, the test body 2 is based on the same conditions as the manufacturing method of the test body 1 except that the non-oxidizing atmosphere of the heat treatment is changed (nitrogen gas containing 10% H ₂ O + 1% H ₂ ). Was made.

<Test body 3>
In the manufacturing method of the test body 1, the test body 3 was produced based on the same conditions as the manufacturing method of the test body 1 except that the heat treatment time was changed (18 hours).

<Test body 4>
In the manufacturing method of the test body 1, the non-oxidizing atmosphere of the heat treatment is changed (only nitrogen gas) and the temperature and time of the heat treatment are changed (800 ° C. × 5 hours). The test body 4 was produced based on the same conditions.

<Test body 5>
In the manufacturing method of the said test body 1, while changing the non-oxidizing atmosphere of heat processing (only nitrogen gas) and changing the temperature and time of heat processing (900 degreeC x 5 hours), the manufacturing method of the said test body 1 The test body 5 was produced based on the same conditions.

<Comparator 1: Ir only>
In the same manner as in the manufacturing method of the test body 1, an amorphous precursor of a support composed of an oxide (a hydroxide of TiO ₂ —ZrO ₂ ) was prepared, and then Ir was 1 wt% with respect to the weight of the support. The precursor is impregnated with an aqueous solution in which H ₂ IrCl ₆ is dissolved at a ratio to be dried and dried (100 ° C. × 24 hours), thereby holding Ir in the precursor. Hereinafter, the exhaust gas-purifying catalyst comparative body 1 was obtained by operating in the same manner as in the manufacturing method of the test body 1 described above.

<Comparator 2: Pt only>
In the same manner as in the manufacturing method of the test body 1, an amorphous precursor of a support made of an oxide (a hydroxide of TiO ₂ —ZrO ₂ ) was prepared, and then Pt was 2 wt% with respect to the weight of the support. The precursor is impregnated with an aqueous solution in which H ₂ PtCl ₄ is dissolved at a ratio to be dried and dried (100 ° C. × 24 hours), thereby holding Pt on the precursor. Thereafter, a comparative body 2 of an exhaust gas purifying catalyst was obtained by operating in the same manner as the manufacturing method of the test body 1 described above.

<Comparator 3: Heat treatment under oxidizing atmosphere>
In the manufacturing method of the test body 1, a comparative body 3 was manufactured based on the same conditions as the manufacturing method of the test body 1 except that the heat treatment was performed in an oxidizing atmosphere (atmosphere).

<Comparative body 4: Direct retention of metal components on the carrier>
An aqueous solution in which H ₂ IrCl ₆ and H ₂ PtCl ₆ are mixed and dissolved at a ratio of 1 wt% Ir and 0.5 wt% Pt with respect to the weight of the carrier is a carrier comprising SiO ₂ (particle size 0.5 to 1 mm) and dried (100 ° C. × 24 hours) to directly hold Ir and Pt on the carrier. Thereafter, the exhaust gas purifying catalyst comparison body 4 was obtained by operating in the same manner as in the manufacturing method of the test body 1 described above.

<Comparator 5: Direct retention of alloy particles on carrier>
Metal Ir pieces and metal Pt pieces are mixed at a ratio of 1 wt% Ir and 0.5 wt% Pt with respect to the weight of the carrier, and arc-melted to pulverize and atomize the resulting alloy particles in water. After being dispersed, impregnated with a carrier made of SiO ₂ (particle size 0.5 to 1 mm) and dried (100 ° C. × 24 hours), heat treatment in the atmosphere (500 ° C. × 2 hours) An exhaust gas purifying catalyst comparative body 5 in which Ir—Pt alloy particles were directly held on the carrier was obtained.

<Comparator 6: Catalyst based on the description of Patent Documents 1 and 2>
An aqueous solution in which H ₂ IrCl ₆ is dissolved at a rate of 1 wt% of Ir with respect to the weight of the carrier is impregnated with a carrier made of TiO ₂ (particle size 0.5 to 1 mm) and dried (120 ° C. × 24 hours) Then, Ir is supported on the carrier by heat treatment in the atmosphere (300 ° C. × 2 hours).

Next, the carrier is dispersed in ion-exchanged water, Pt (NO ₂ ) ₂ (NH ₃ ) ₂ is added at a ratio of 0.5 wt% with respect to the weight of the carrier, and Na ₂ SO _3. 5H ₂ O, Na ₂ SO ₃ , C ₆ H ₇ NaO ₆ .H ₂ O was added to adjust the pH (pH = 6.21), the mixture was stirred (24 hours), filtered, washed with water, and dried (120 Of the exhaust gas purification catalyst in which Pt is laminated on part of the surface of Ir by heat-reducing in the atmosphere (500 ° C. × 2 hours). Comparative body 6 was obtained.

[B. experimental method]
<A. Presence / absence of solid solution alloying of active ingredients and average particle size>
The presence / absence of solid solution alloying of the active components of the test bodies 1 to 5 and the comparative bodies 1 to 6 and the average particle size were determined based on the measurement results by XRD. That is, based on the peak position measured by XRD, the face spacing (d (111)) is obtained, and the face spacing (reference value) of Ir and Pt is compared, and the active ingredient is determined based on its size and position. The presence or absence of alloying was determined, and the average particle size value of the active component was determined by half-width analysis (Scherrer's formula) of the peak measured by XRD. In addition, in the comparative body 5, it measured and calculated | required by XRD before making the produced alloy particle carry | supported to a support | carrier.

<B. Denitration rate>
For each sample (2 cm ³ ) of the test bodies 1 to 5 and the comparative bodies 1 to 6 manufactured as described above, a test gas having the following composition is heated to a predetermined temperature while circulating under the following conditions: The nitrogen oxide concentration in the test gas flowing through the sample was measured, and the denitration rate at the temperature at that time was determined based on the nitrogen oxide concentration in the test gas before flowing the sample.

《Test gas composition》
・ NO: 900ppm
・ SO ₂ : 900 ppm
・ C ₃ H ₆ : 900 ppm
・ O ₂ : 15%
・ H ₂ O: 5%
・ N ₂ : Remaining

《Test gas supply conditions》
・ GHSV: 6500h ^-1
・ AV: 5.5Nm ³ / m ² h

[C. Experimental result]
<A. Presence / absence of solid solution alloying of active ingredients and average particle size value>
Table 1 below shows the presence / absence of solid-solution alloying of the active ingredient and the average particle size determined as described above.

  As can be seen from Table 1 above, in the test bodies 1 to 5, the interplanar spacing (d (111)) determined from the XRD measurement results is clearly different from the interplanar spacing of Ir and Pt (document values). It was confirmed that the active component was formed into a solid solution alloy and that the average particle size was in the range of 10 to 50 nm.

  On the other hand, in the comparative body 5, although the active component is an alloy particle in which the active component is dissolved, the average particle diameter can only be at the μm level. In the comparative bodies 1 to 4, 6, the average particle diameter of the active ingredient is Although it is within the range of 10 to 50 nm, the surface distance (d (111)) determined from the XRD measurement results is substantially the same as the surface distance (document value) of Ir or Pt, so that the active ingredient is in solution. It was confirmed that they existed without becoming alloy particles. In Comparative Examples 3, 4, and 6, Pt could not be measured because the peak intensity was much smaller than Ir.

<B. Denitration rate>
Next, the measurement experiment results of the denitration rate are shown in FIGS.

  As is apparent from FIGS. 3 to 13, in the test bodies 1 to 5, it was confirmed that nitrogen oxides can be decomposed at a denitration rate of 10% or more over the entire temperature range of 250 to 450 ° C. On the other hand, in Comparative bodies 1 to 6, it was confirmed that nitrogen oxides could not be decomposed at a denitration rate of 10% or more over the entire temperature range of 250 to 450 ° C.

  The exhaust gas purifying catalyst according to the present invention can efficiently decompose nitrogen oxides over a wide temperature range of 250 to 450 ° C. The method for producing an exhaust gas purifying catalyst according to the present invention includes the present invention. Such an exhaust gas purifying catalyst can be easily manufactured, and the exhaust gas purifying method according to the present invention is capable of producing nitrogen over the entire temperature range of the exhaust gas, even if it is exhaust gas from a diesel engine whose temperature varies widely depending on the load condition. Since the oxide can be decomposed efficiently, the present invention can be used extremely beneficially industrially.

It is a flowchart showing the procedure of embodiment of the manufacturing method of the exhaust gas purification catalyst which concerns on this invention. It is explanatory drawing of embodiment of the manufacturing method of the catalyst for exhaust gas purification which concerns on this invention. 3 is a graph showing the relationship between the temperature and the denitration rate in the test body 1. 4 is a graph showing the relationship between the temperature and the denitration rate in the test body 2. 3 is a graph showing the relationship between the temperature and the denitration rate in the test body 3. 3 is a graph showing the relationship between the temperature and the denitration rate in the test body 4. 4 is a graph showing the relationship between the temperature and the denitration rate in the test body 5. 3 is a graph showing the relationship between the temperature and the denitration rate in the comparative body 1. 4 is a graph showing the relationship between the temperature and the denitration rate in comparative body 2. 5 is a graph showing the relationship between the temperature and the denitration rate in the comparative body 3. 4 is a graph showing the relationship between the temperature and the denitration rate in the comparative body 4. 5 is a graph showing the relationship between the temperature and the denitration rate in the comparative body 5. 7 is a graph showing the relationship between the temperature and the denitration rate in the comparative body 6.

Explanation of symbols

110 exhaust gas purifying catalyst 111 support 111a precursor 112 alloy particles 112a and 112b metal components

Claims (10)

A support made of an oxide;
An alloy particle supported on the carrier and having a plurality of metal components dissolved therein,
A catalyst for exhaust gas purification, wherein the alloy particles have a particle size of 100 nm or less. In claim 1,
Wherein said _{carrier, TiO 2, SiO 2, Al} 2 O 3, ZrO 2, CaO, MgO, exhaust gas-purifying catalyst characterized by comprising a SnO _2, at least two or more composite oxides of ZnO. In claim 1,
The catalyst for exhaust gas purification, wherein the alloy particles are at least two kinds of solid solutions of Pt, Ir, Pd, Rh, Ru, Au, and Ag. In claim 3,
The exhaust gas purifying catalyst, wherein the alloy particles are a solid solution of two kinds of metal components containing at least Ir and have a particle size of 10 nm or more. In claim 1,
The exhaust gas purifying catalyst, wherein the alloy particles are supported at a ratio of 0.1 to 5 wt% with respect to the carrier. A method for producing an exhaust gas purifying catalyst according to any one of claims 1 to 5,
The amorphous precursor of the carrier made of an oxide contains a solution in which a metal component is dissolved, and the precursor is held with a plurality of metal components, and then the precursor is heat-treated in a non-oxidizing atmosphere. The method for producing an exhaust gas purifying catalyst is characterized in that the alloy particles in which a plurality of the metal components are dissolved are supported on the support made of oxide by changing the structure. In claim 6,
The method for producing an exhaust gas purifying catalyst, wherein the non-oxidizing atmosphere comprises at least one of a reducing gas and an inert gas. In claim 6,
The method for producing an exhaust gas purifying catalyst, wherein the non-oxidizing atmosphere contains water vapor. An exhaust gas purification method comprising decomposing a nitrogen oxide in the exhaust gas by bringing the exhaust gas purification catalyst according to any one of claims 1 to 5 into contact with the exhaust gas. In claim 9,
The exhaust gas is a gas having a temperature of 250 to 450 ° C discharged from a diesel engine.

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