JP4720592B2 - Electrochemical catalyst for exhaust gas purification - Google Patents
Electrochemical catalyst for exhaust gas purification Download PDFInfo
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Description
本発明は、自動車や小型発電装置などに使用される内燃機関や、ファンヒータやストーブなどの暖房機、焼却炉などから排出される可燃性ガス（炭化水素、一酸化炭素等）、ＮＯｘを含む排ガスに含まれる可燃性ガス、ＮＯｘを浄化する燃焼排ガスに含まれる可燃性ガス、及び、ＮＯｘなどの排ガスを浄化する排ガス浄化用電気化学触媒に関する。 The present invention includes NOx, combustible gas (hydrocarbon, carbon monoxide, etc.) exhausted from internal combustion engines used in automobiles, small power generators, heaters such as fan heaters and stoves, incinerators, etc. The present invention relates to a combustible gas contained in exhaust gas, a combustible gas contained in combustion exhaust gas for purifying NOx, and an exhaust gas purifying electrochemical catalyst for purifying exhaust gas such as NOx.
従来の自動車などの内燃機関に使用される排ガスの可燃性ガスやＮＯｘを浄化する触媒としては、三元触媒に代表されるように、排ガス中に含まれるＮＯやＮＯ2などの窒素酸化物を窒素へ還元する反応と、排ガス中の炭化水素や一酸化炭素（ＣＯ）や水素（Ｈ2）などの還元性物質（以下、このような還元性物質を代表的にＨＣとする）を酸化させる反応とを同一の触媒上で行い、高効率に浄化を行う方法が実用化されている。 As a catalyst for purifying flammable gas and NOx of exhaust gas used in conventional internal combustion engines such as automobiles, as represented by a three-way catalyst, nitrogen oxides such as NO and NO 2 contained in the exhaust gas are used. Reaction to reduce to nitrogen and oxidize reducing substances such as hydrocarbons, carbon monoxide (CO) and hydrogen (H 2 ) in the exhaust gas (hereinafter, such reducing substances are typically referred to as HC). A method in which the reaction is carried out on the same catalyst and purification is carried out with high efficiency has been put into practical use.
そして、触媒材料としては、Ｐｔ、Ｒｈ、Ｐｄ等の貴金属をアルミナ等の担体基材に担持したものが主として用いられている。 As the catalyst material, a material in which a noble metal such as Pt, Rh, or Pd is supported on a carrier substrate such as alumina is mainly used.
特に、近年では、このような排ガス浄化用触媒として、特許文献１、特許文献２などに記載されているようなＮＯｘ還元触媒とＨＣ酸化触媒とＨＣ吸着材料と混合伝導性材料から構成された電気化学触媒が提案されている。 In particular, in recent years, as such an exhaust gas purification catalyst, an electric power composed of a NOx reduction catalyst, an HC oxidation catalyst, an HC adsorbing material, and a mixed conductive material as described in Patent Document 1, Patent Document 2, and the like. Chemical catalysts have been proposed.
この排ガス浄化用電気化学触媒では、ＮＯｘの還元で生じた酸素イオンを酸化触媒まで移動させ、その酸素を使って、酸化触媒上でＨＣを酸化している。この構成の場合、ＮＯｘ還元触媒とＨＣ酸化触媒の性能が電気化学触媒の性能を支配しており、触媒材料としてＯｓ、Ｉｒ、Ｒｕ、Ｐｔ、Ｒｈ、Ｐｄといった貴金属材料を用いている。
近年、地球規模での環境に対する意識の高まりから、排気ガスの浄化は質量ともに要求水準が上がってきている。このような状況から、従来用いられてきた触媒では、貴金属の需要が広がり、供給不足とそれに伴う更なるコストの上昇が懸念される。 In recent years, with the increasing awareness of the environment on a global scale, the required level of exhaust gas purification is increasing both in terms of mass. Under such circumstances, with the conventionally used catalysts, the demand for noble metals is widened, and there is a concern that supply shortages and accompanying costs increase.
本発明は、上記問題に鑑みてなされたものであり、貴金属を用いることなく触媒機能を発揮する排ガス浄化用電気化学触媒を実現することを目的とする。 This invention is made | formed in view of the said problem, and it aims at implement | achieving the electrochemical catalyst for exhaust gas purification which exhibits a catalyst function, without using a noble metal.
上記目的を達成するため、鋭意検討した結果、本発明者は、貴金属ではない金属であっても、異なる種類の金属または金属酸化物よりなる材料の間の電子状態の差によって、排ガスを還元ないし酸化できることを、実験的に見出した。 As a result of diligent studies to achieve the above object, the present inventor reduced or reduced the exhaust gas by the difference in electronic state between materials made of different types of metals or metal oxides, even metals that are not precious metals. It was experimentally found that it can be oxidized.
すなわち、本発明の排ガス浄化用電気化学触媒は、イオン伝導性と電子伝導性とを併せ持つ混合伝導性の第１の物質と、金属または金属酸化物よりなる２種以上の第２の物質とにより構成され、異なる種類の第２の物質の間を、第１の物質を介してイオンと電子が移動するものであり、第１の物質は、Ｌａ ０．６５ Ｓｒ ０．３５ ＭｎＯ ３ であり、第２の物質は、ＴｉＯ ２ とＣｕＯであることを特徴とする。 That is, the exhaust gas purifying electrochemical catalyst of the present invention comprises a mixed conductive first material having both ionic conductivity and electronic conductivity, and two or more second materials made of metal or metal oxide. Configured to transfer ions and electrons between different types of second materials via the first material, the first material being La 0.65 Sr 0.35 MnO 3 , The second substance is characterized by being TiO 2 and CuO .
それによれば、異なる種類の第２の物質の間を、混合導電性を持つ第１の物質を介してイオンと電子が移動するため、本発明の触媒によって、排ガスの分解反応を発生させることができる。よって、本発明によれば、貴金属を用いることなく触媒機能を発揮する排ガス浄化用電気化学触媒を実現することができる。 According to this, since ions and electrons move between different kinds of second substances via the first substance having mixed conductivity, the catalyst of the present invention can generate an exhaust gas decomposition reaction. it can. Therefore, according to the present invention, it is possible to realize an exhaust gas purifying electrochemical catalyst that exhibits a catalytic function without using a noble metal.
また、第２の物質を、ナノレベルサイズの粒子であって第１の物質に担持されたものとすることが好ましい。ここで、ナノレベルサイズの粒子とは、粒径が１００ｎｍ以下のものである。このように、第２の物質をナノレベルのサイズとすることで触媒の比表面積を稼ぐことができ、好ましい。 In addition, it is preferable that the second substance is nano-level sized particles supported on the first substance. Here, the nano-level sized particles are those having a particle size of 100 nm or less. Thus, the specific surface area of the catalyst can be increased by making the second substance have a nano-level size, which is preferable.
以下、本発明の実施形態について図に基づいて説明する。図１は、本発明の実施形態に係る排ガス浄化用電気化学触媒１００の構成を模式的に示す図である。用途限定するものではないが、本実施形態の排ガス浄化用電気化学触媒１００は、例えば自動車の排ガス浄化を行うものとして説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration of an exhaust gas purifying electrochemical catalyst 100 according to an embodiment of the present invention. Although the application is not limited, the exhaust gas purifying electrochemical catalyst 100 of the present embodiment will be described as purifying exhaust gas of an automobile, for example.
図１に示されるように、本実施形態の排ガス浄化用電気化学触媒１００は、イオン伝導性と電子伝導性とを併せ持つ混合伝導性材料である第１の物質１０と、金属または金属酸化物よりなる２種以上の第２の物質２１、２２とにより構成されている。 As shown in FIG. 1, the exhaust gas purifying electrochemical catalyst 100 of the present embodiment includes a first substance 10 that is a mixed conductive material having both ionic conductivity and electronic conductivity, and a metal or metal oxide. And two or more types of second substances 21 and 22.
ここで、第１の物質１０は、イオン伝導性と電子伝導性とを併せ持つことにより、異なる種類の第２の物質２１と２２との間に介在して、これら第２の物質２１、２２間でイオンと電子とを移動させる機能を有する。 Here, the first substance 10 has both ionic conductivity and electron conductivity, so that the first substance 10 is interposed between different types of second substances 21 and 22, so that the second substance 21 and 22 are interposed. And has a function of moving ions and electrons.
そのような機能を有する第１の物質としては、Ｓｍ、Ｃｅ、Ｌａ、Ｐｒ、Ｎｄ、Ｇｄ、Ｅｒ、Ｙ、Ｂｉ、Ｂａ、Ｓｒ、Ｃａ、Ｋ、Ｐｂ、Ｔｉ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ａｌ、Ｚｒ、Ｙｂからなる元素の群から選ばれた少なくとも２種以上の元素を有して構成された複合酸化物材料などが挙げられる。 As the first substance having such a function, Sm, Ce, La, Pr, Nd, Gd, Er, Y, Bi, Ba, Sr, Ca, K, Pb, Ti, Mn, Fe, Co, Ni A composite oxide material composed of at least two elements selected from the group consisting of Cu, Al, Zr, and Yb.
また、図１に示される例では、第２の物質２１、２２は２種類としている。また、この第２の物質２１、２２は、例えば１００ｎｍ以下のナノレベルサイズの粒子であり、焼成などにより、第１の物質１０の表面に担持されたものとなっている。 Moreover, in the example shown by FIG. 1, the 2nd substances 21 and 22 are made into two types. The second substances 21 and 22 are, for example, nano-sized particles having a size of 100 nm or less, and are supported on the surface of the first substance 10 by firing or the like.
本例では、片方の第２の物質２１は、ＮＯを還元する還元側の第２の物質２１であり、他方の第２の物質２２は、ＨＣすなわち炭化水素だけでなくＨ2、ＣＯなどを含む還元性物質を酸化する酸化側の第２の物質２２である。 In this example, the second material 21 of one is a second material 21 of the reduction side for reducing NO, second material 22 of the other, not only HC i.e. hydrocarbons H 2, CO, etc. It is the second substance 22 on the oxidation side that oxidizes the reducing substance that it contains.
これら還元側の第２の物質２１および酸化側の第２の物質２２は、金属材料または金属酸化物材料よりなるが、当然ながら、両第２の物質２１と２２とでは、物質を構成する金属材料または金属酸化物材料の種類は異なるものである。 The reducing-side second substance 21 and the oxidizing-side second substance 22 are made of a metal material or a metal oxide material. Of course, both the second substances 21 and 22 are metals constituting the substance. The type of material or metal oxide material is different.
ここで、上述のように、還元側の第２の物質２１と酸化側の第２の物質２２との間で、第１の物質１０を介したイオンおよび電子の移動が可能となっているが、これは、異なる材料よりなる両第２の物質２１、２２の間で、仕事関数またはフェルミ準位が異なるためと推定される。 Here, as described above, it is possible to transfer ions and electrons through the first substance 10 between the second substance 21 on the reduction side and the second substance 22 on the oxidation side. This is presumed to be because work functions or Fermi levels are different between the second substances 21 and 22 made of different materials.
例えば、還元側の第２の物質２１と酸化側の第２の物質２２とが異なる金属材料よりなる場合には、これら両第２の物質２１、２２間には仕事関数に差があり、還元側の第２の物質２１の方が、仕事関数が高く、酸化側の第２の物質２２の方が、仕事関数が低いものとなる。 For example, when the second substance 21 on the reduction side and the second substance 22 on the oxidation side are made of different metal materials, there is a difference in work function between the second substances 21 and 22, and the reduction The second material 21 on the side has a higher work function, and the second material 22 on the oxidation side has a lower work function.
一方、還元側の第２の物質２１と酸化側の第２の物質２２とが異なる金属酸化物材料よりなる場合には、両者２１、２２間にはフェルミ準位に差があり、還元側の第２の物質２１の方が、フェルミ準位が高く、酸化側の第２の物質２２の方が、フェルミ準位が低いものとなる。 On the other hand, when the second substance 21 on the reduction side and the second substance 22 on the oxidation side are made of different metal oxide materials, there is a difference in Fermi level between the two substances 21 and 22, The second substance 21 has a higher Fermi level, and the second substance 22 on the oxidation side has a lower Fermi level.
これら還元側の第２の物質２１および酸化側の第２の物質２２としては、Ｐｔなどの貴金属を除く金属元素が用いられる。具体的には、これら第２の物質２１、２２として、Ｓｍ、Ｃｅ、Ｌａ、Ｐｒ、Ｎｄ、Ｇｄ、Ｅｒ、Ｙ、Ｂｉ、Ｂａ、Ｓｒ、Ｃａ、Ｋ、Ｐｂ、Ｔｉ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ａｌ、Ｚｒ、Ｙｂ、Ｚｎからなる元素の群から選ばれた元素を有して構成されたものなどが挙げられる。 As the second substance 21 on the reduction side and the second substance 22 on the oxidation side, metal elements other than noble metals such as Pt are used. Specifically, these second substances 21 and 22 include Sm, Ce, La, Pr, Nd, Gd, Er, Y, Bi, Ba, Sr, Ca, K, Pb, Ti, Mn, Fe, Co. , Ni, Cu, Al, Zr, Yb, and Zn, and the like.
例えば、この元素の群からＴｉとＣｕとを選んだ場合、第２の物質２１、２２としては、ＴｉまたはＴｉ酸化物を有して構成されるものとＣｕまたはＣｕ酸化物を有して構成されるものとの２種となる。そして、この場合においては、２種のうち仕事関数またはフェルミ準位の高い方を還元側の第２の物質２１とし、仕事関数またはフェルミ準位の低い方を酸化側の第２の物質２２とする。 For example, when Ti and Cu are selected from this group of elements, the second materials 21 and 22 are composed of Ti or Ti oxide and composed of Cu or Cu oxide. It becomes two kinds with what is done. In this case, the higher work function or Fermi level of the two types is used as the second substance 21 on the reduction side, and the lower work function or Fermi level is used as the second substance 22 on the oxidation side. To do.
こうして、本実施形態の排ガス浄化用電気化学触媒１００においては、電子（ｅ-）の流れとイオン種として酸素イオン（Ｏ2-）を用いた場合、図１中の矢印に示されるように、電子およびイオンの流れが示され、第２の物質２１、２２間をイオンと電子の双方が移動可能な電気化学触媒１００が構成されている。 Thus, in the exhaust gas purifying electrochemical catalyst 100 of the present embodiment, when oxygen ions (O 2− ) are used as the flow of electrons (e − ) and ion species, as shown by the arrows in FIG. The flow of electrons and ions is shown, and an electrochemical catalyst 100 is configured in which both ions and electrons can move between the second substances 21 and 22.
なお、本実施形態の排ガス浄化用電気化学触媒１００は、ペレット状に成形したり、セラミックス製のハニカムや、ハニカム以外の連通孔を有する形状や多孔質形状を有する担体などに塗布したりすることにより、排ガスの可燃性ガス及びＮＯｘ浄化に使用することができる。 The exhaust gas-purifying electrochemical catalyst 100 of the present embodiment is formed into a pellet shape, or applied to a ceramic honeycomb, a shape having a communication hole other than a honeycomb, or a carrier having a porous shape. Therefore, it can be used for purifying combustible gas and NOx of exhaust gas.
本実施形態の排ガス浄化用電気化学触媒１００についての、具体的な組成や製造方法、評価結果等については、後述の実施例に示すこととし、次に、図１を参照して、本実施形態の作用効果について説明する。 The specific composition, manufacturing method, evaluation results, and the like of the exhaust gas purifying electrochemical catalyst 100 of the present embodiment will be shown in examples described later. Next, referring to FIG. The operational effects of will be described.
図１に示されるように、本実施形態の触媒１００は、ＮＯやＨＣ、ＣＯなどを含む排ガス雰囲気に置かれているとき、これら排ガスを分解するものである。 As shown in FIG. 1, the catalyst 100 of the present embodiment decomposes the exhaust gas when placed in an exhaust gas atmosphere containing NO, HC, CO, and the like.
まず、２種の第２の物質２１、２２として金属材料を用いた場合を説明する。仕事関数の高い金属材料である還元側の第２の物質２１に吸着したＯ2やＮＯは、電子を供与されて、Ｏ2はＯ2-にイオン化され、ＮＯはＮ2とＯ2-に分解される。これらの分解の具体的な反応式は、次の化学式１に示される。 First, the case where a metal material is used as the two types of second substances 21 and 22 will be described. O 2 or NO adsorbed on the second substance 21 on the reducing side, which is a metal material having a high work function, is donated with electrons, O 2 is ionized into O 2− , and NO is converted into N 2 and O 2− . Disassembled. A specific reaction formula of these decompositions is shown in the following chemical formula 1.
（化１）
ＮＯ＋２ｅ− → １／２Ｎ2＋Ｏ2-
Ｏ2＋４ｅ− → ２Ｏ2-
そして、Ｏ2-は混合伝導体である第１の物質１０中を通過して、仕事関数の低い金属材料である酸化側の第２の物質２２に移動する。この酸化側の第２の物質２２で、Ｏ2-はＨＣを酸化し、二酸化炭素と水を生成する。
(Chemical formula 1)
NO + 2e- → 1 / 2N 2 + O 2-
O 2 + 4e- → 2O 2-
Then, O 2− passes through the first substance 10 which is a mixed conductor and moves to the second substance 22 on the oxidation side which is a metal material having a low work function. In the second substance 22 on the oxidation side, O 2− oxidizes HC to generate carbon dioxide and water.
また、同様に、酸化側の第２の物質２２では、ＣＯ、Ｈ2も分解する。また、ＨＣが存在しない場合は、Ｏ2を生成する。その際発生する余剰電子は、第１の物質１０中を通過して還元側の第２の物質２１に移動し、Ｏ2-の生成に使用される。これら酸化側の第２の物質２２側における分解の具体的な反応式は、次の化学式２に示される。 Similarly, in the second substance 22 on the oxidation side, CO and H 2 are also decomposed. If HC does not exist, O 2 is generated. The surplus electrons generated at this time pass through the first substance 10 and move to the second substance 21 on the reduction side, and are used to generate O 2− . A specific reaction formula of the decomposition on the second substance 22 side on the oxidation side is represented by the following chemical formula 2.
（化２）
Ｏ2-＋ＨＣ → Ｈ2Ｏ＋ＣＯ2＋２ｅ−
１／２Ｏ2-＋ＣＯ → ＣＯ2＋ｅ−
Ｏ2-＋Ｈ2 → Ｈ2Ｏ＋２ｅ−
２Ｏ2- → Ｏ2＋４ｅ−
次に２種の第２の物質２１、２２として、金属酸化物材料を用いた場合を説明する。フェルミ準位の高い金属材料である還元側の第２の物質２１に吸着したＯ2やＮＯは、電子を供与されて、Ｏ2はＯ2-にイオン化され、ＮＯはＮ2とＯ2-に分解される。
(Chemical formula 2)
O 2− + HC → H 2 O + CO 2 + 2e−
1 / 2O 2- + CO → CO 2 + e-
O 2− + H 2 → H 2 O + 2e−
2O 2- → O 2 + 4e-
Next, the case where a metal oxide material is used as the two types of second substances 21 and 22 will be described. O 2 and NO adsorbed to the second material 21 of the Fermi level of a metal material having high reduction side are donating electrons, O 2 is ionized into O 2-, NO is N 2 and O 2- Is broken down into
そして、Ｏ2-は第１の物質１０中を通過して、フェルミ準位の低い金属である酸化側の第２の物質２２に移動する。酸化側の第２の物質２２で、Ｏ2-はＨＣを酸化し、二酸化炭素と水を生成するとともに、ＣＯ、Ｈ2も分解する。 Then, O 2− passes through the first substance 10 and moves to the second substance 22 on the oxidation side, which is a metal having a low Fermi level. In the second substance 22 on the oxidation side, O 2− oxidizes HC to generate carbon dioxide and water, and also decomposes CO and H 2 .
また、この場合も、ＨＣが存在しない場合は、Ｏ2を生成し、その際発生する余剰電子は、第１の物質１０中を通過して還元側の第２の物質２１に移動し、Ｏ2-の生成に使用される。なお、この金属酸化物材料を用いた場合の分解の化学反応式も、上記化学式１、化学式２と同様である。 Also in this case, when the HC is not present, generates O 2, excess electrons generated at that time, moved to the first of the second material 21 to pass through the material 10 of the reduction side, O Used to generate 2- The chemical reaction formula of decomposition when using this metal oxide material is the same as the chemical formula 1 and chemical formula 2.
このように、本実施形態の電気化学触媒１００では、２種以上の金属材料または金属酸化物材料が、混合伝導体によって接続されることで、ＮＯの分解（還元）反応とＨＣの酸化反応によって、いわゆる局部電池が構成され、外部電源から電力を供給しなくても、燃焼排ガスの可燃性ガス及び、ＮＯｘを浄化できる。 As described above, in the electrochemical catalyst 100 of the present embodiment, two or more kinds of metal materials or metal oxide materials are connected by the mixed conductor, so that NO decomposition (reduction) reaction and HC oxidation reaction occur. In other words, a so-called local battery is configured, and the combustible gas and NOx of the combustion exhaust gas can be purified without supplying power from an external power source.
よって、本実施形態によれば、貴金属を用いることなく触媒機能を発揮する排ガス浄化用電気化学触媒１００を実現することができる。また、本実施形態では、第２の物質２１、２２を、ナノレベルサイズの微粒子とすることで触媒の比表面積を稼ぐことができ、また、活性が向上する。 Therefore, according to this embodiment, the exhaust gas-purifying electrochemical catalyst 100 that exhibits a catalytic function without using a noble metal can be realized. Moreover, in this embodiment, the specific surface area of a catalyst can be earned and the activity improves by making the 2nd substances 21 and 22 into nano level size microparticles | fine-particles.
次に、実施例に基づいて、本実施形態の排ガス浄化用電気化学触媒についての具体的な組成や製造方法、評価結果について説明するが、もちろん、これらにより本発明が限定されるものではない。 Next, specific compositions, production methods, and evaluation results for the exhaust gas purifying electrochemical catalyst of the present embodiment will be described based on examples, but of course the present invention is not limited thereto.
［サンプル調整］
金属酸化物よりなる第２の物質として、ｎ型半導体性を有しフェルミ準位が高いＴｉＯ2（還元側の第２の物質に相当）と、ｐ型半導体性を有しフェルミ準位が低いＣｕＯ（酸化側の第２の物質に相当）とを用いた。各材料は、シーアイ化成製ナノ粒子（水系溶媒に分散、１５ｗｔ％）を用いた。平均粒径は、ＴｉＯ2が３６ｎｍであり、ＣｕＯが４８ｎｍである。
[Sample adjustment]
As a second substance made of a metal oxide, an n-type Fermi level is higher TiO 2 has a semiconductor property (corresponding to the second material of reduced side), a low Fermi level has a p-type semiconductor properties CuO (corresponding to the second substance on the oxidation side) was used. As each material, nanoparticles made by CI Kasei (dispersed in an aqueous solvent, 15 wt%) were used. The average particle size is 36 nm for TiO 2 and 48 nm for CuO.
混合伝導体としての第１の物質には、Ｌａ0.65Ｓｒ0.35ＭｎＯ3を用いた。Ｌａ2Ｏ3、ＳｒＣＯ3、ＭｎＣＯ3を所定量秤量し、ボールミル法（ＺｒＯ2ボール）で２０時間混合後、空気フロー状態（５．０ｌ／ｍｉｎ）で９５０℃で１２時間処理して作製した。その後、ボールミル法（ＺｒＯ2ボール）で４時間粉砕し、平均粒径が約１．０μｍの粉末を作製した。 La 0.65 Sr 0.35 MnO 3 was used as the first material as the mixed conductor. A predetermined amount of La 2 O 3 , SrCO 3 , and MnCO 3 was weighed, mixed for 20 hours by a ball mill method (ZrO 2 ball), and then processed at 950 ° C. for 12 hours in an air flow state (5.0 l / min). . Thereafter, the mixture was pulverized by a ball mill method (ZrO 2 balls) for 4 hours to produce a powder having an average particle size of about 1.0 μm.
評価サンプルは、Ｌａ0.65Ｓｒ0.35ＭｎＯ3を１ｇに付き、ＴｉＯ2分散溶液０．２２５ｇ、ＣｕＯ分散溶液０．４７５ｇ、純水１０ｇを加え、攪拌した。その後、１５０℃で乾燥し、粉末状よりなる実施例の電気化学触媒を作製した。得られた粉末のＳＥＭ写真を図２に示す。 The evaluation sample was 1 g of La 0.65 Sr 0.35 MnO 3 , 0.225 g of TiO 2 dispersion solution, 0.475 g of CuO dispersion solution, and 10 g of pure water were added and stirred. Then, it dried at 150 degreeC and produced the electrochemical catalyst of the Example which consists of a powder form. An SEM photograph of the obtained powder is shown in FIG.
このように、ＳＥＭ観察により、第１の物質であるＬａ0.65Ｓｒ0.35ＭｎＯ3の表面に第２の物質であるＴｉＯ2とＣｕＯとが担持された排ガス浄化用電気化学触媒が形成されていることが確認された。 Thus, by SEM observation, an exhaust gas purifying electrochemical catalyst in which TiO 2 and CuO as second substances are supported on the surface of La 0.65 Sr 0.35 MnO 3 as a first substance is formed. Was confirmed.
また、比較のため、Ｌａ0.65Ｓｒ0.35ＭｎＯ3のみのサンプル（比較例１）、ＴｉＯ2のみを担持したサンプル（比較例２）、ＣｕＯのみを担持したサンプル（比較例３）も用意した。 For comparison, La 0.65 Sr 0.35 MnO 3 samples only (Comparative Example 1), the sample (Comparative Example 2) carrying only TiO 2, the sample (Comparative Example 3) carrying only CuO was also prepared.
［評価試験］
実施例及び比較例１〜３の粉末サンプルを用いてＨＣ及びＮＯｘの浄化性能を測定した。効果の確認を容易にするため、ＨＣとＮＯｘをそれぞれ単独に評価した。
[Evaluation test]
The purification performance of HC and NOx was measured using the powder samples of Examples and Comparative Examples 1 to 3. In order to facilitate the confirmation of the effect, HC and NOx were evaluated independently.
図３は、評価装置の構成の一例を示す図である。石英管３１の中に磁製ボート３２を設置し、この磁製ボート３２にサンプルＫを設置するようになっている。石英管３１の両端開口部は、栓３３により封止されている。 FIG. 3 is a diagram illustrating an example of the configuration of the evaluation apparatus. A magnetic boat 32 is installed in the quartz tube 31, and a sample K is installed in the magnetic boat 32. Openings at both ends of the quartz tube 31 are sealed with plugs 33.
また、一方の栓３３には、評価ガスを石英管３１に導入する導入路３４が設けられ、他方の栓３３には、石英管３１を通過した評価ガスを排出する排出路３５が設けられている。また、石英管３１の外側には、石英管３１を加熱し所望温度に設定するためのヒータ３６が設けられている。 One plug 33 is provided with an introduction path 34 for introducing the evaluation gas into the quartz tube 31, and the other plug 33 is provided with a discharge path 35 for discharging the evaluation gas that has passed through the quartz tube 31. Yes. Further, a heater 36 for heating the quartz tube 31 and setting it to a desired temperature is provided outside the quartz tube 31.
このような評価装置において、石英管３１に導入されサンプルＫを通過し排出路３５から排出されたガスは、図示しないガスクロマトグラフなどのガス分析装置に供給され、その成分が検出されるようになっている。 In such an evaluation apparatus, the gas introduced into the quartz tube 31 and passing through the sample K and discharged from the discharge path 35 is supplied to a gas analyzer such as a gas chromatograph (not shown), and its components are detected. ing.
このような評価装置を用いて、磁製ボート３２に各サンプルＫをそれぞれ１ｇ載せ、石英管３１内に設置した。そして、１００ｐｐｍのＣ3Ｈ6、４５０ｐｐｍのＯ2、バランスガスとしてＮ2を用いた混合ガス（ストイキ組成）を２００ｍＬ／ｍｉｎで流し、Ｃ3Ｈ6濃度の減少をガスクロマトグラフ（島津製作所製ＧＣ−１４Ｂ）で測定した。その結果を表１に示す。 Using such an evaluation apparatus, 1 g of each sample K was placed on the porcelain boat 32 and placed in the quartz tube 31. Then, a mixed gas (stoichiometric composition) using 100 ppm of C 3 H 6 , 450 ppm of O 2 and N 2 as a balance gas was flowed at 200 mL / min, and the reduction of the C 3 H 6 concentration was measured by a gas chromatograph (Shimadzu Corporation GC). -14B). The results are shown in Table 1.
この表１に示されるように、比較例１〜３に比べ、実施例では、Ｃ3Ｈ6濃度が３０％減少する温度が約５０℃低下した。つまり、実施例のものは、ＨＣの分解性能が向上することが確認された。 As shown in Table 1, the temperature at which the C 3 H 6 concentration was reduced by 30% decreased by about 50 ° C. in Examples compared to Comparative Examples 1 to 3 . That is, it was confirmed that the HC decomposition performance was improved in the examples.
さらに、５０ｐｐｍのＮＯ、８％のＯ2、バランスガスとしてＮ2を用いた混合ガスを１Ｌ／ｍｉｎで流し、ＮＯ濃度の減少をＮＯｘ計（島津製作所製ＮＯＡ−７０００）で測定した。その結果を表２に示す。 Further, a mixed gas using 50 ppm NO, 8% O 2 and N 2 as a balance gas was flowed at 1 L / min, and the decrease in NO concentration was measured with a NOx meter (NOA-7000, manufactured by Shimadzu Corporation). The results are shown in Table 2.
この表２に示されるように、比較例１に比べ、実施例では、ＮＯ分解が開始する温度が約１００℃低下した。つまり、実施例のものは、ＮＯの分解性能が向上することが確認された。 As shown in Table 2, as compared with Comparative Example 1, in the example, the temperature at which NO decomposition starts was reduced by about 100 ° C. In other words, it was confirmed that the NO decomposition performance was improved in the examples.
このように、Ｃ3Ｈ6酸化およびＮＯ分解において、ＴｉＯ2、ＣｕＯそれぞれ単独では触媒作用は見られないが、ＴｉＯ2、ＣｕＯの双方を担持した実施例は、触媒作用が向上している。 As described above, in C 3 H 6 oxidation and NO decomposition, TiO 2 and CuO alone do not show a catalytic action, but the examples supporting both TiO 2 and CuO have improved catalytic action.
なお、上記実施形態では、第２の物質は、第１の物質に担持されたものであったが、異なる種類の第２の物質の間を、第１の物質を介してイオンと電子が移動するようになっていれば、第２の物質は第１の物質に担持されていなくてもよい。 In the above embodiment, the second substance is supported on the first substance. However, ions and electrons move between the different kinds of second substances via the first substance. If it comes to do, the 2nd substance does not need to be carry | supported by the 1st substance.
また、上記実施形態では、第２の物質２１、２２は２種類であったが、異なる金属材料または金属酸化物材料であれば、３種類もしくはそれ以上の種類の第２の物質を有するものであってもよい。 In the above embodiment, there are two types of the second substances 21 and 22. However, if they are different metal materials or metal oxide materials, they have three or more types of second substances. There may be.
１０…第１の物質、２１…還元側の第２の物質、２２…酸化側の第２の物質。 10 ... first substance, 21 ... second substance on the reduction side, 22 ... second substance on the oxidation side.
Claims (2)
前記第１の物質は、Ｌａ ０．６５ Ｓｒ ０．３５ ＭｎＯ ３ であり、
前記第２の物質は、ＴｉＯ ２ とＣｕＯであることを特徴とする排ガス浄化用電気化学触媒。 A mixed conductive first material having both ionic conductivity and electronic conductivity, and two or more types of second materials made of metal or metal oxide, between the different types of the second materials. And ions and electrons move through the first substance ,
The first material is La 0.65 Sr 0.35 MnO 3 ;
The exhaust gas purifying electrochemical catalyst, wherein the second substance is TiO 2 and CuO .
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