JP2017192933A - Exhaust gas purification catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas purifying catalyst excellent in achieving both economic efficiency and exhaust gas purification performance.SOLUTION: There is provided an exhaust gas purifying catalyst which comprises a carrier containing YMnOand Ag and Mn and/or Ni supported by a carrier, wherein the Ag and Mn and/or Ni are supported in an amount of 1/9 or more and 9/1 or less in the mass ratio AgO/(MnOand/or NiO) in terms of oxides. The amount of Ag preferably is less than 1 mass% in the total 100 mass% of the carrier and Ag and the molar ratio between Mn and Y in the carrier preferably is 2 or less.SELECTED DRAWING: None

Description

The present invention relates to an exhaust gas purifying catalyst containing YMn ₂ O ₅ .

  Exhaust gas emitted from internal combustion engines such as gasoline engines and diesel engines such as automobiles and motorcycles (also referred to as saddle-type vehicles) contains harmful components such as HC and CO. Conventionally, an oxidation catalyst has been used for the purpose of purifying and detoxifying these harmful components. As such an oxidation catalyst, an arbitrary combination of a noble metal such as Pt, Pd, and Rh and alumina, ceria, zirconia, or a composite oxide thereof is used.

In recent years, an exhaust purification catalyst in which YMn ₂ O ₅ is used as a carrier as a yttrium manganate composite compound (hereinafter also referred to as “YMO”) and silver is supported thereon has been reported. Patent Document 1 discloses a double oxide Y _1-X A _X Mn _2-Z B _Z O ₅ (wherein A is La, Sr, Ce, Ba, Ca, Sc, Ho, Er, Tm, Yb, Lu). Or Bi, B is Co, Fe, Ni, Cr, Mg, Ti, Nb, Ta, Cu or Ru, 0.5 ≧ X ≧ 0 and 1 ≧ Z ≧ 0) Exhaust gas having at least one atom selected from the group consisting of Ag, Pt, Au, Pd, Rh, Cu, and Mn supported on the double oxide Y _1-X A _X Mn _2-Z B _Z O ₅ A gas purification catalyst is described. In an example of Patent Document 1, an exhaust gas purifying catalyst is described in which Ag or Mn is individually supported on a carrier powder made of YMn ₂ O ₅ .

Patent Document 2 discloses a compound oxide having a DyMn ₂ O ₅ structure in which the A site contains Y and the B site contains Mn, and the B / A composition ratio B / A is larger than 2. An exhaust gas purifying catalyst characterized in that it contains is described. Patent Document 2 describes that the double oxide in the exhaust gas purifying catalyst may carry Ag.
Patent Document 3 describes an exhaust gas purifying catalyst in which silver is supported on a carrier containing YMnO ₃ .

WO2012 / 093599 pamphlet JP2013-233541A WO2012 / 093600 pamphlet

  However, since the catalysts described in Patent Documents 1 to 3 use expensive Ag, they are not sufficient in that they exhibit excellent exhaust gas purification performance while reducing raw material costs.

  An object of the present invention is to provide an exhaust gas purifying catalyst that can eliminate the various disadvantages of the above-described prior art.

The present invention includes a support containing YMn ₂ O ₅ , Ag and Mn and / or Ni supported on the support,
For exhaust gas purification, Ag and Mn and / or Ni are supported in an amount of 1/9 to 9/1 in the mass ratio Ag ₂ O / (MnO ₂ and / or NiO) in terms of oxide A catalyst is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the catalyst for exhaust gas purification excellent in the point which is compatible with economical efficiency and exhaust gas purification performance is provided.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
The exhaust gas purifying catalyst of the present embodiment has a support containing YMn ₂ O ₅ . In the present specification, the carrier allows not only the function of supporting the catalyst but also the one that itself has an exhaust gas purification action. The exhaust gas purifying catalyst of this embodiment has, for example, a powder form.

YMn ₂ O ₅ is not limited to the production method, and any commercially available product can be used. Examples of the method for manufacturing YMn ₂ O _5, include the same manner as described in the pamphlet No. WO2012 / 093599. That is, Y ₂ O ₃ and MnO ₂ as raw materials are weighed so that the Y / Mn atomic ratio becomes 1/2, and pulverized and mixed preferably for 3 hours or more using a ball mill or the like. Thereafter, the composite oxide is fired in an air atmosphere, preferably 800 ° C. or higher and 1100 ° C. or lower, more preferably 850 ° C. or higher and 950 ° C. or lower, preferably 1 hour or longer and 24 hours or shorter, more preferably 4 hours or longer and 10 hours or shorter. and a method of obtaining a YMn ₂ O _5.

It can be confirmed that the exhaust gas purifying catalyst of this embodiment contains YMn ₂ O ₅ by, for example, subjecting the exhaust gas purifying catalyst to X-ray diffraction measurement. For example, in the X-ray diffraction measurement of the exhaust gas purifying catalyst using CuKα ray as the radiation source, YMn is in the range of 2θ = 28 ° to 30 °, 30 ° to 32 °, and 33 ° to 35 °. ₂ O ₅ (121) plane, (211) plane, (130) when a peak derived from the surface is observed, the catalyst for purifying exhaust gases, said to include _YMn 2 _{O 5.} Further, in the exhaust gas purifying catalyst, YMn ₂ O ₅ supports Ag, Mn, and Ni as carriers, for example, on the premise that the presence of YMn ₂ O ₅ is confirmed in the catalyst, X-ray photoelectron spectroscopy Exhaust gas purification catalyst in which the ratio (molar fraction) of each mole number of Ag, Mn, and Ni to the moles of all metal atoms present on the powder surface measured by ICP is measured by ICP emission spectrometry Can be confirmed by confirming that it is larger than the ratio (molar fraction) of the respective moles of Ag, Mn, and Ni with respect to the moles of all metal atoms in the solution obtained by dissolving by melting with alkali or the like.

The carrier containing YMn ₂ O ₅ is usually in a powder form. The average particle diameter (D ₅₀ ) is 1 μm or more and 20 μm or less from the viewpoint that the supported amount of Ag, Mn, and Ni is easily adjusted and suitable for use as an exhaust gas purification catalyst. It is preferably 5 μm or more and 15 μm or less. The average particle diameter (D ₅₀ ) is an integrated volume 50% particle diameter measured by a laser diffraction / scattering particle size distribution measuring method. For example, an automatic sample feeder for a laser diffraction particle diameter distribution measuring apparatus (“Microtorac SDC” manufactured by Nikkiso Co., Ltd.) The sample powder is put into a water-soluble solvent and irradiated with a 40 W ultrasonic wave at a flow rate of 40% for 360 seconds, and then measured using a Microtrac MT3300II manufactured by Nikkiso Co., Ltd. or Microtrac. Measurement conditions are determined as an average value of particle refractive index 1.5, particle shape true sphere, solvent refractive index 1.3, set zero 30 seconds, measurement time 30 seconds, and twice measurement.

The molar ratio Mn / Y of Mn and Y in the carrier containing YMn ₂ O ₅ is preferably 2 or less. Specifically, the carrier having a molar ratio of Mn / Y of 2 or less is, for example, YMn ₂ O ₅ itself or YMn ₂ O ₅ in addition to Y. If Y is present, the HC adsorption site provided by Y itself exhibits not only YMn ₂ O ₅ but also HC adsorption by Y, and it is considered that the HC purification performance is superior to YMO having Mn / Y exceeding ₂ . YMn ₂ O ₅ itself is also considered to be superior in HC purification performance compared to YMO having Mn / Y exceeding ₂ for reasons such as stability. On the other hand, Mn / Y is preferably 1 or more from the viewpoint of maintaining a high specific surface area by maintaining a constant amount of YMn ₂ O ₅ in the carrier and enhancing the exhaust gas purification action of the catalyst of the present embodiment. More preferably, it is 1.5 or more. The molar ratio of Mn to Y in the carrier can be measured by ICP emission spectroscopy or fluorescent X-ray analysis. In general, the carrier made of YMn ₂ O ₅ is designed so that Mn / Y is 2.

  Preferably, the exhaust gas purifying catalyst of the present embodiment does not substantially contain an yttrium manganate composite compound having a molar ratio Mn / Y of more than 2, as described in Patent Document 2. Specifically, in the exhaust gas purifying catalyst of the present embodiment, the content of the yttrium manganate composite compound having a molar ratio Mn / Y of more than 2 is, for example, 20% by mass or less from the viewpoint of heat resistance. It is preferable that it is 10 mass% or less.

In the exhaust gas purification catalyst of the present embodiment, the ratio of the carrier is preferably 75% by mass or more from the viewpoint of exerting the exhaust gas purification action by YMn ₂ O ₅ itself, and is 95% by mass or less. Ag, Mn, Ni to be supported on the carrier and, if necessary, the amount of the binder used for supporting them is more than a certain amount, which is preferable from the viewpoint of improving the adhesion strength and the exhaust gas purification action in the exhaust gas purification catalyst. . From this viewpoint, the proportion of the carrier in the exhaust gas purification catalyst of the present embodiment is preferably 85% by mass or more and 95% by mass or less.

The proportion of YMn ₂ O _{5 in} the carrier is preferably 50% by mass or more from the viewpoint of sufficiently exhibiting a good exhaust gas purifying catalyst by YMn ₂ O ₅ . The proportion of YMn ₂ O _{5 in} the carrier is preferably as high as possible. For example, it is preferably 70% by mass or more, and more preferably 80% by mass or more. Proportion of YMn ₂ O ₅ in the carrier was measured by the intensity ratio of the strongest line content YMn ₂ O ₅ in the exhaust gas purifying catalyst by X-ray diffraction (the strongest intensity peaks), relative to the amount of the carrier It can be obtained by determining the ratio. The amount of the carrier is measured by measuring the amount of metal supported on the carrier by X-ray diffraction measurement, X-ray photoelectron spectroscopy, ICP-AES, etc., and subtracting the amount of the supported metal from the whole. be able to.

One of the features of the exhaust gas purifying catalyst of the present embodiment is that the amount of Ag supported is small. Specifically, the supported amount of Ag is less than 1% by mass of Ag in a total of 100% by mass of the carrier and Ag. Ag is expensive, and the exhaust gas purifying catalyst of the present embodiment is exhausted even if the amount of Ag used in this way is reduced by containing a specific metal together with Ag in YMn ₂ O ₅ as described later. Gas purification action is high. On the other hand, in Patent Documents 1 and 2, in many examples in which Ag is supported on a carrier, Ag is 5% by mass or 5.57% by mass in a total of 100% by mass of the carrier and Ag. This ratio is 2% by mass even in the smallest example (Example 22 described in the patent document). As described above, the technology for enhancing the exhaust gas purification effect when the amount of Ag carried on the carrier containing YMn ₂ O ₅ is reduced has not been studied in Patent Documents 1 and 2, and the present inventors have made the first attempt. It has been studied. In addition, the amount of Ag here is the amount in terms of Ag metal.

  The amount of Ag in the exhaust gas purifying catalyst is 0.05% by mass or more in a total of 100% by mass of the carrier and Ag. The effect of improving the exhaust gas purifying effect by combining Ag and a specific metal From the viewpoint of increasing Further, the amount of Ag is preferably less than 1% by mass in the total of 100% by mass of the support and Ag, since the raw material cost is reduced and the economic effect of combining Ag with a specific metal is increased. From these viewpoints, the amount of Ag in the exhaust gas purifying catalyst is more preferably 0.08% by mass or more and 0.98% by mass or less in a total of 100% by mass of the carrier and Ag.

The present inventors diligently studied a technique for maintaining the exhaust gas purification action of the catalyst while reducing the amount of Ag in the exhaust gas purification catalyst. As a result, it has been found that when a specific amount of Ag is replaced with a specific metal, the exhaust gas purification action can be surprisingly maintained as compared to before replacement. Specifically, in the exhaust gas purifying catalyst of the present embodiment, Ag and Mn and / or Ni are 1/9 or more and 9 or more in terms of oxide-based mass ratio Ag ₂ O / (MnO ₂ and / or NiO). One feature is that it is supported on the carrier in an amount of 1 or less. In this specification, whether or not it is an oxide equivalent amount, the amount of “Mn and / or Ni” is the amount that is supported when only one of Mn and Ni is supported on the support. In the case where both Mn and Ni are supported on the support, the total amount of Mn and Ni supported on the support is indicated.

In the exhaust gas purifying catalyst of the present embodiment, the mass ratio Ag ₂ O / (MnO ₂ and / or) in which the amount ratio of Ag supported on the carrier and Mn and / or Ni supported on the carrier is an oxide equivalent. By being 1/9 or more in NiO), the amount of Ag can be secured and the exhaust gas purification performance can be enhanced. Further, when the quantitative ratio of Ag to Mn and / or Ni is 9/1 or less in the mass ratio, the exhaust gas purification performance is improved by combining Ag and Mn and / or Ni. An effect is obtained. From these viewpoints, in particular, the quantitative ratio of Ag to Mn and / or Ni is 1/5 or more 5 / in the mass ratio Ag ₂ O / (MnO ₂ and / or NiO) in terms of oxide. It is preferably 1 or less, and particularly preferably 1/3 or more and 3/1 or less. In addition, the description of oxide conversion here does not prescribe | regulate the presence form of Ag and Mn and / or Ni which were carry | supported by the support | carrier in the exhaust gas purification catalyst. In the exhaust gas purifying catalyst, Mn or Ni supported on the carrier is usually present in the form of MnO ₂ or NiO, but Ag is present in the form of metal metal.

The supported Mn and / or Ni may be either Mn or Ni, or both. When both are supported, the mass ratio (MnO ₂ / NiO) in terms of oxide of both is preferably 1/3 or more and 3/1 or less from the viewpoint of the purification balance of HC and CO. Of Mn or Ni, an exhaust gas purification catalyst having Mn has a high HC purification action, and an exhaust gas purification catalyst having Ni has a high CO purification action.

  Furthermore, when the exhaust gas purifying catalyst of the present embodiment contains Mn supported on a carrier, the amount of Mn supported is supported on the carrier, Ag, the Mn and, if necessary, the carrier contained. From the viewpoint of obtaining an effect of improving the exhaust gas purification effect by using Mn, it is preferably 0.06% by mass or more in a total of 100% by mass with Ni. The amount of Mn supported on the carrier is 0.57% by mass or less of the total of 100% by mass of the carrier, Ag, Mn, and Ni supported on the carrier contained as necessary. This is preferable because the effect of purifying exhaust gas per added amount is increased. From these viewpoints, the amount of Mn supported on the carrier is 0.06 mass in a total of 100 mass% of the carrier, Ag, the supported Mn, and Ni supported on the carrier contained as necessary. % To 0.50% by mass is more preferable. The amounts of Ag, Mn and Ni here are amounts in terms of metal.

  Further, when the exhaust gas purifying catalyst of this embodiment contains Ni supported on a carrier, the amount of Ni is the sum of the carrier, Ag, Ni, and Mn supported on the carrier contained as necessary. From 100% by mass, 0.08% by mass or more is preferable from the viewpoint of obtaining an effect of improving the exhaust gas purification effect by using Ni. The amount of Ni is 0.71% by mass or less per 100% by mass of the total of 100% by mass of the carrier, Ag, Ni, and Mn supported on the carrier contained as necessary. It is preferable because the exhaust gas purification effect is enhanced. From these viewpoints, the amount of Ni supported on the carrier is 0.08% by mass or more and 0.000% by mass in 100% by mass in total with the carrier, Ag, Ni, and Mn supported on the carrier contained as necessary. More preferably, it is 70 mass% or less. The amounts of Ag, Mn and Ni here are amounts in terms of metal.

  The amount of Ag supported on the carrier can be measured by measuring the amount of Ag in the solution obtained by dissolving the exhaust gas purifying catalyst by alkali melting or the like by ICP-AES. The amount of Mn supported on the carrier is determined based on the X-ray diffraction measurement by measuring the amount of Y and Mn in the solution obtained by dissolving the exhaust gas purification catalyst by alkali melting or the like with ICP-AES. It can be measured by subtracting the amount of Mn of the carrier from the amount of Mn in the solution based on the Y: Mn ratio in the obtained carrier. Furthermore, the amount of Ni supported on the carrier can be measured by measuring the amount of Ni in a solution obtained by dissolving the exhaust gas purifying catalyst by alkali melting or the like by ICP-AES.

The exhaust gas purifying catalyst may contain other compounds in addition to YMn ₂ O ₅ , Ag, Mn (MnO ₂ ), and Ni (NiO). Examples of compounds other than YMn ₂ O ₅ constituting the carrier include YMO compounds such as YMnO ₃ and Y ₂ Mn ₂ O ₇ . In addition, as a compound other than YMn ₂ O ₅ constituting the carrier, a part of Y in YMn ₂ O ₅ is replaced with another element, for example, La, Sr, Ce, Ba, Ca as described in Patent Document 1. , Sc, Ho, Er, Tm, Yb, Lu, Bi or the like, or a part of Mn with other elements, for example, Co, Fe, Ni, Cr, Mg as described in Patent Document 1 , Ti, Nb, Ta, Cu, Ru or the like. Further, in the exhaust gas purification catalyst, Pt, Au, Pd, Rh, and Cu may be supported on a carrier in addition to Ag, Mn, and Ni. Further, the exhaust gas purifying catalyst may use a binder for supporting Ag, Mn, and Ni on YMn ₂ O _5, and the binder in that case is an inorganic water-soluble solution such as alumina sol or zirconia sol. Is used. When the binder is used, the content thereof is preferably 5% by mass or more and 15% by mass or less in the exhaust gas purification catalyst from the viewpoint of not impairing the catalytic action and the adhesion strength of the exhaust gas purification catalyst.

In order to support Ag and Mn and / or Ni on a carrier containing YMn ₂ O ₅ , it is preferable to immerse the carrier in a solution containing Ag and Mn and / or Ni, and then to dry and fire. As Ag, Mn, and Ni salt used for the preparation of a solution containing Ag and Mn and / or Ni, for example, oxalate, acetate, nitrate, ammine complex salt, chloride and the like are used. As the solvent, water or the like can be used. Firing is preferably performed at 450 ° C. to 600 ° C. for 1 hour to 3 hours in an air atmosphere.

  The exhaust gas purifying catalyst in which Ag and Mn and / or Ni are supported on the support as described above exhibits stable catalytic ability even when exposed to a high temperature of about 900 ° C. or higher and 1150 ° C. or lower. Such an exhaust gas purification catalyst can exhibit stable and high exhaust gas purification performance as an exhaust gas purification catalyst of an internal combustion engine that uses fossil fuel as a power source such as a gasoline engine or a diesel engine. In particular, the exhaust gas purifying catalyst of the present embodiment is preferably used for purifying exhaust gas discharged from gasoline engines such as automobiles and motorcycles because of its high heat resistance. The exhaust gas purifying catalyst of the present embodiment is effectively used particularly for removing carbon monoxide (CO) and / or hydrocarbon (HC) in the exhaust gas.

The exhaust gas purifying catalyst of the present embodiment can be used as a catalyst layer supported on a catalyst support. The catalyst support is made of, for example, ceramics or a metal material. The shape of the catalyst support is not particularly limited, but is generally a honeycomb shape, a plate, a pellet, a DPF or the like, and preferably a honeycomb or a DPF. The material of such a catalyst support, e.g., alumina _{(Al 2 O} 3), mullite _{(3Al 2 O 3 -2SiO 2)} , cordierite _{(2MgO-2Al 2 O 3 -5SiO} 2), titanate Examples thereof include ceramics such as aluminum (Al ₂ TiO ₅ ) and silicon carbide (SiC), and metal materials such as stainless steel.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”.

[Example 1]
YMn ₂ O ₅ powder _(D 50: 10.0 [mu] m), silver nitrate (AgNO _3), manganese nitrate (II) 6 hydrate _{(Mn (NO 3) 2 ·} 6H 2 O), and an inorganic binder (a zirconia sol ) Were prepared. As a support, a stainless steel metal honeycomb support (300 cells, φ40 mm × L60 mm, capacity 75.4 cc) was fired at 500 ° C. for 1 hour to remove oil and dust adhering to the support.
215 g of water was added to 2.377 g of silver nitrate (AgNO ₃ ) and 0.600 g of manganese nitrate (II) hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O) and stirred to obtain an aqueous solution of silver nitrate and manganese nitrate. 179.46 g of YMn ₂ O ₅ powder was added to the aqueous solution. After stirring for 2 hours, 57.14 g of an inorganic binder was added to obtain a YMn ₂ O ₅ -containing slurry.

Next, after immersing the stainless steel metal honeycomb support in a slurry containing YMn ₂ O ₅ , the excess slurry in the cell is removed by air blowing and dried, followed by firing at 500 ° C. for 1 hour in an air atmosphere. A catalyst layer was formed, and the exhaust gas purifying catalyst of Example 1 was obtained. In the produced exhaust gas purification catalyst, the supported amount of YMn ₂ O ₅ was 133.65 g per liter of the catalyst in terms of oxide. Further, the molar ratio Mn / Y of Mn and Y in the carrier was 2.
Carrier in the resulting exhaust gas purifying catalyst _(YMn 2 _{O 5)} to supported the Ag, the mass ratio of the oxide in terms of Mn and Ni, the sum of Ag that is supported with the carrier _(YMn 2 _{O 5)} 100 Table 1 shows the ratio of Ag in% and the ratio of Mn and Ni supported in a total of 100% of the support (YMn ₂ O ₅ ) and supported Ag, Mn and Ni. In Example 1, the ratio of the carrier in the exhaust gas purifying catalyst was 89.1% by mass (the same applies to Examples 2 to 7 described later). In the obtained exhaust gas purification catalyst, Ag is present as a metal metal, Mn supported on YMn ₂ O ₅ is present as MnO ₂ , and Ni supported on YMn ₂ O ₅ is present as NiO. (Examples 2 to 7 were also the same).

[Example 2]
Example 1 except that the amount of silver nitrate (AgNO ₃ ) was 1.321 g and the amount of manganese nitrate (II) hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O) was 3.001 g. Thus, an exhaust gas purification catalyst was obtained. About the obtained exhaust gas purifying catalyst, Ag supported on the support (YMn ₂ O ₅ ), mass ratio in terms of oxides of Mn and Ni, the total of the support (YMn ₂ O ₅ ) and the supported Ag Table 1 shows the ratio of Ag in 100%, and the ratio of Mn and Ni supported in a total of 100% of the support (YMn ₂ O ₅ ), supported Ag, Mn and Ni. The molar ratio Mn / Y between Mn and Y in the carrier was 2.

Example 3
Example 1 except that the amount of silver nitrate (AgNO ₃ ) was 0.264 g and the amount of manganese nitrate (II) hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O) was 5.402 g. Thus, an exhaust gas purification catalyst was obtained. About the obtained exhaust gas purifying catalyst, Ag supported on the support (YMn ₂ O ₅ ), mass ratio in terms of oxides of Mn and Ni, the total of the support (YMn ₂ O ₅ ) and the supported Ag Table 1 shows the ratio of Ag in 100%, and the ratio of Mn and Ni supported in a total of 100% of the support (YMn ₂ O ₅ ), supported Ag, Mn and Ni. The molar ratio Mn / Y between Mn and Y in the carrier was 2.

Example 4
Instead of manganese nitrate (II) hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O) 0.600 g, nickel nitrate (II) hexahydrate (Ni (NO ₃ ) ₂ .6H ₂ O) 0 Exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that .715 g was used. The obtained exhaust gas purifying catalyst, the support _(YMn 2 _{O 5)} to supported the Ag, the mass ratio of the oxide in terms of Mn and Ni, and the metal is supported with the carrier _(YMn 2 _{O 5)} X Table 1 shows the ratio of the metal X in a total of 100%. The molar ratio Mn / Y between Mn and Y in the carrier was 2.

Example 5
The amount of silver nitrate (AgNO ₃₎ and 1.321G, instead of manganese nitrate (II) 6 hydrate _{(Mn (NO 3) 2 ·} 6H 2 O) 0.600g, nickel nitrate (II) 3.576g Exhaust gas purification catalyst was obtained in the same manner as in Example 1 except that it was used. About the obtained exhaust gas purifying catalyst, Ag supported on the support (YMn ₂ O ₅ ), mass ratio in terms of oxides of Mn and Ni, the total of the support (YMn ₂ O ₅ ) and the supported Ag Table 1 shows the ratio of Ag in 100%, and the ratio of Mn and Ni supported in a total of 100% of the support (YMn ₂ O ₅ ), supported Ag, Mn and Ni. The molar ratio Mn / Y between Mn and Y in the carrier was 2.

Example 6
The amount of silver nitrate (AgNO ₃₎ and 0.264 g, instead of manganese nitrate (II) 6 hydrate _{(Mn (NO 3) 2 ·} 6H 2 O) 0.600g, nickel nitrate (II) 6.436g Exhaust gas purification catalyst was obtained in the same manner as in Example 1 except that it was used. About the obtained exhaust gas purifying catalyst, Ag supported on the support (YMn ₂ O ₅ ), mass ratio in terms of oxides of Mn and Ni, the total of the support (YMn ₂ O ₅ ) and the supported Ag Table 1 shows the ratio of Ag in 100%, and the ratio of Mn and Ni supported in a total of 100% of the support (YMn ₂ O ₅ ), supported Ag, Mn and Ni. The molar ratio Mn / Y between Mn and Y in the carrier was 2.

Example 7
Silver nitrate (AgNO ₃₎ the amount of the 1.321G, instead of manganese nitrate (II) 6 hydrate _{(Mn (NO 3) 2 ·} 6H 2 O) 0.600g, manganese nitrate (II) 6 hydrate An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that 1.501 g and 1.788 g of nickel (II) nitrate were used. The obtained exhaust gas purifying catalyst, the carrier mass ratios of oxides in terms of _(YMn 2 _{O 5)} to supported the Ag, Mn and Ni, and Ag that is supported with the carrier _(YMn 2 _{O 5)} Table 1 shows the ratio of Ag in 100% in total, and the ratio of Mn and Ni supported in the total of 100% of the support (YMn ₂ O ₅ ), Ag, Mn and Ni supported. The molar ratio Mn / Y between Mn and Y in the carrier was 2.

[Comparative Example 1]
Exhaust gas purification of Comparative Example 1 in the same manner as in Example 1 except that silver nitrate (AgNO ₃ ) and manganese nitrate (II) hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O) are not used. A catalyst was obtained.

[Comparative Example 2]
Except that manganese nitrate (II) hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O) was not used and the amount of silver nitrate (AgNO ₃ ) was 0.264 g, the same as in Example 1, An exhaust gas purifying catalyst of Comparative Example 2 was obtained.

  The obtained exhaust gas purifying catalyst was subjected to durable firing at 1100 ° C. in the atmosphere for 4 hours, and then subjected to the following evaluation. The results are shown in Table 3.

Each catalyst obtained in Examples and Comparative Examples was charged into a 100 mg flow reactor, and flowed at 25 L / min of model gas for evaluation (model gas of exhaust gas from a gasoline engine) having the composition shown in Table 2 below. The temperature was raised to 500 ° C. at a rate of 20 ° C./min, then cooled to 50 ° C., again raised to 500 ° C. at a rate of temperature rise of 20 ° C./min, and the light-off temperature T50 for CO and HC purification was measured. The results are shown in Table 3. T50 is the gas temperature at the inlet of the apparatus when the evaluation model gas temperature flowing into the apparatus in which the complex oxide powder is arranged is gradually increased from room temperature and the CO and HC purification rate reaches 50%. The total hydrocarbon amount was measured using an FID detector, and the CO concentration was measured using PG-240 manufactured by Horiba. Note values in Table 2 is the volume ratio than the amount of C ₃ H _6.

As shown in Table 3, the catalyst powder of each example is composed of YMn ₂ O ₅ and Ag, Mn and / or Ni, and the mass ratio Ag ₂ O / (MnO ₂ and / or Ni in terms of oxide). It can be seen that the NiO) is supported in an amount of 1/9 or more and 9/1 or less, so that even if the amount of Ag is small, the temperature of T50 is low and an excellent exhaust gas purification action is exhibited.

Claims (7)

A carrier containing YMn ₂ O ₅ , Ag and Mn and / or Ni supported on the carrier,
For exhaust gas purification, Ag and Mn and / or Ni are supported in an amount of 1/9 to 9/1 in the mass ratio Ag ₂ O / (MnO ₂ and / or NiO) in terms of oxide catalyst.   The exhaust gas purifying catalyst according to claim 1, wherein Ag is less than 1 mass% in a total of 100 mass% of the carrier and Ag.   The exhaust gas purifying catalyst according to claim 1 or 2, wherein a molar ratio Mn / Y of Mn to Y in the carrier is 2 or less.   The exhaust gas purification catalyst according to any one of claims 1 to 3, wherein the exhaust gas purification catalyst is used to purify exhaust gas discharged from a gasoline engine.   The exhaust gas purification catalyst according to any one of claims 1 to 4, wherein a ratio of the carrier in the exhaust gas purification catalyst is 75 mass% or more. The exhaust gas purifying catalyst according to any one of claims 1 to 5, wherein a ratio of YMn ₂ O _{5 in} the carrier is 50 mass% or more. A method of purifying exhaust gas using a catalyst powder containing a carrier containing YMn ₂ O ₅ and Ag and Mn and / or Ni supported on the carrier,
In the catalyst powder, Ag and Mn and / or Ni are supported on the carrier in an amount of 1/9 or more and 9/1 or less in the mass ratio Ag ₂ O / (MnO ₂ and / or NiO) in terms of oxide. Is there a way to purify the exhaust gas.