JP4753613B2 - NOx purification catalyst - Google Patents
NOx purification catalyst Download PDFInfo
- Publication number
- JP4753613B2 JP4753613B2 JP2005127099A JP2005127099A JP4753613B2 JP 4753613 B2 JP4753613 B2 JP 4753613B2 JP 2005127099 A JP2005127099 A JP 2005127099A JP 2005127099 A JP2005127099 A JP 2005127099A JP 4753613 B2 JP4753613 B2 JP 4753613B2
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- JP
- Japan
- Prior art keywords
- catalyst
- platinum
- heat
- resistant material
- precursor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 238000000746 purification Methods 0.000 title claims description 32
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- 239000002243 precursor Substances 0.000 claims description 33
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- 239000000377 silicon dioxide Substances 0.000 claims description 19
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Description
本発明は排ＮＯｘ浄化用触媒としての耐熱性材料で被覆した白金含有触媒に関するものであり、この触媒を用いることによってディーゼル自動車の排ガスに含まれるＮＯｘを長期間高効率で浄化処理できる。 The present invention relates to a platinum-containing catalyst coated with heat-resistant material as waste the NO x purification catalyst can purify treated long-term with high efficiency NO x contained in the exhaust gas of a diesel automobile by using this catalyst.
ガソリン自動車の排ガス浄化用触媒の主流となっている三元触媒は、触媒支持体としてコージェライトのモノリス成形体を用い、該成型体のガス流路内壁に触媒である数100nm〜数μmの大きさの白金-パラジウム-ロジウム粒子を含んだ数μm〜数十μmの大きさの活性アルミナ粒子を塗布した構造となっている。活性アルミナ粒子は数10nm〜数100nmの微粒子の凝集体であり、微粒子間の間隙に触媒粒子が吸着している。三元触媒はガソリン車の排ガス処理には非常に有効であるが、軽油燃料で走行するディーゼル車の排ガス処理にはほとんど効果がない。特に、過渡走行時に排出される150〜300℃の排ＮＯｘを浄化するための触媒開発は触媒化学の分野においても未解決である。そして、現在でも、ディーゼル車の排ガス処理のための実用的な触媒は知られていない。 The three-way catalyst, which is the mainstream of exhaust gas purification catalysts for gasoline automobiles, uses a cordierite monolith molded body as a catalyst support and has a size of several hundred nm to several μm as a catalyst on the inner wall of the gas flow path of the molded body. In this structure, activated alumina particles having a size of several μm to several tens of μm containing platinum-palladium-rhodium particles are coated. The activated alumina particles are aggregates of fine particles of several tens nm to several hundreds nm, and the catalyst particles are adsorbed in the gaps between the fine particles. The three-way catalyst is very effective for the exhaust gas treatment of gasoline vehicles, but has little effect on the exhaust gas treatment of diesel vehicles running on light oil fuel. In particular, the catalyst development for purifying exhaust NO x of 150 to 300 ° C. discharged during a transient traveling is outstanding in the field of catalytic chemistry. Even now, no practical catalyst for treating exhaust gas from diesel vehicles is known.
その主な理由は、上記三元触媒がディーゼル排ガスにおける比較的高濃度の酸素雰囲気下で著しい活性低下を起こすことからきている。ガソリン車の排ガスの酸素濃度は１％以下であるが、軽油の空燃比はガソリンの空燃比の数倍以上であるのでディーゼルの排ガスに含まれる酸素濃度は通常５％以上である。ガソリン車の場合は、空気と燃料の理論的重量混合比を示す理論空燃比近傍で燃焼させることで共存酸素を1％以下に制御しているのでこの燃焼はリッチバーンとよばれているが、ディーゼル燃料の燃焼は吸気量が理論値よりも大過剰であるので燃料供給量が相対的に少ないのでリーンバーンとよばれている。この燃焼の条件で酸素濃度が５％になると三元触媒の活性がほとんど失活するからである。 The main reason is that the three-way catalyst causes a significant decrease in activity in a relatively high concentration oxygen atmosphere in diesel exhaust gas. The oxygen concentration of exhaust gas from gasoline vehicles is 1% or less, but since the air-fuel ratio of light oil is more than several times the air-fuel ratio of gasoline, the oxygen concentration contained in diesel exhaust gas is usually 5% or more. In the case of a gasoline vehicle, the coexistence oxygen is controlled to 1% or less by burning near the theoretical air-fuel ratio indicating the theoretical weight mixing ratio of air and fuel, so this combustion is called rich burn, The combustion of diesel fuel is called lean burn because the amount of intake air is much larger than the theoretical value and the fuel supply is relatively small. This is because the activity of the three-way catalyst is almost deactivated when the oxygen concentration becomes 5% under these combustion conditions.
また、ディーゼル排ガス処理を困難にしている他の要因は燃料中のイオウ分による触媒被毒である。イオウ分によって性能劣化した触媒を連続再生使用する方法としては、定期的に750〜850℃のリーンバーン排ガスを触媒充填部に噴射することによる触媒表面の吸着イオウ分の脱着処理が考えられる。しかし、この方法を用いると、通常、再生後の触媒粒子はシンタリング（微粒子が構成元素の拡散移動により大粒子に成長する過程をいう。焼結ともいう。）による粒成長を起こしているので、劣化前のフレッシュ触媒が有していた触媒活性が再生後には維持されないという困難な問題を生じる。ガソリン車に用いられている三元触媒がディーゼル排ガス処理に使用できないもう一つの理由は、イオウ分の被毒を受けやすいことと、シンタリングが原因で起きる再生処理後の触媒活性の低下である。上記問題を解決するための方策としては、触媒の耐酸化性向上と触媒のシンタリング防止であるが、これらの問題を解決するような触媒は未だ見いだされていないのが現状である。 Another factor that makes diesel exhaust gas treatment difficult is catalyst poisoning caused by sulfur in the fuel. As a method of continuously regenerating and using a catalyst whose performance has been deteriorated due to the sulfur content, a desorption treatment of the adsorbed sulfur content on the catalyst surface by periodically injecting a lean burn exhaust gas at 750 to 850 ° C. into the catalyst filling portion can be considered. However, when this method is used, the regenerated catalyst particles usually cause grain growth by sintering (a process in which fine particles grow into large particles due to diffusion movement of constituent elements, also called sintering). This causes a difficult problem that the catalytic activity of the fresh catalyst before deterioration is not maintained after regeneration. Another reason why the three-way catalyst used in gasoline cars cannot be used for diesel exhaust gas treatment is that it is susceptible to sulfur poisoning and reduced catalytic activity after regeneration due to sintering. . Measures for solving the above problems include improving the oxidation resistance of the catalyst and preventing the sintering of the catalyst. However, the present situation is that no catalyst has yet been found to solve these problems.
最近、コア-シェル構造を有する金属超微粒子の形成が注目されている。これは、有機合成の分野とエレクトロニクス材料及び磁気材料の分野で開発された手法であり、多くの合成法が報告されている。代表的な方法として、例えば、非特許文献１〜9にコア-シェル構造を有する超微粒子の製造方法が報告されている。コア成分は金属又は金属化合物の超微粒子であるがシェル成分は金属又は金属化合物の他にシリカ、ジルコニア、チタニア、イットリア、グラファイト、カーボン等の例も報告されている。製造方法の基本は、如何にしてコア成分である金属のナノ粒子を安定に得るかということであり、この考えは100年以上も前に行なわれた金属コロイドの研究に遡ることができるが、当時の科学技術では生成した金属コロイドの凝集防止及び安定化技術が未開拓であったために成功に至らなかった。 Recently, formation of ultrafine metal particles having a core-shell structure has attracted attention. This is a technique developed in the field of organic synthesis and in the fields of electronic materials and magnetic materials, and many synthesis methods have been reported. As a typical method, for example, Non-Patent Documents 1 to 9 report methods for producing ultrafine particles having a core-shell structure. The core component is an ultrafine particle of a metal or a metal compound, but examples of the shell component such as silica, zirconia, titania, yttria, graphite, carbon, etc. have been reported in addition to the metal or metal compound. The basis of the manufacturing method is how to stably obtain the metal nanoparticles as the core component, and this idea can be traced back to the colloidal metal research conducted more than 100 years ago. Science and technology at that time was not successful because the technology for preventing and stabilizing the agglomeration of the colloidal metal produced was undeveloped.
一方、工業的な触媒は多孔性材料に担持した状態で使用されることが多い。多孔性材料の細孔は、ＩＵＰＡＣによると、細孔直径が2nm以下のミクロ細孔、2〜50nmのメソ細孔、及び50nm以上のマクロ細孔に分類されている。したがって本発明ではメソ細孔を有する材料は特にメソポーラス材料と言うことにする。ミクロからメソの範囲にわたる広い分布をもつような単一の多孔性材料は活性炭以外には知られていない。近年、数nmの位置に細孔ピークをもち、比表面積が400〜1100m2/gという非常に大きな値を有するシリカ、アルミナ、及びシリカアルミナ系メソポーラス材料が開発された。これらは、例えば、特許文献１〜３に開示されている。 On the other hand, industrial catalysts are often used in a state of being supported on a porous material. According to IUPAC, the pores of the porous material are classified into micropores having a pore diameter of 2 nm or less, mesopores of 2 to 50 nm, and macropores of 50 nm or more. Therefore, in the present invention, a material having mesopores is particularly referred to as a mesoporous material. No single porous material other than activated carbon has a wide distribution ranging from the micro to meso range. In recent years, silica, alumina, and silica-alumina mesoporous materials having a pore peak at a position of several nm and a very large specific surface area of 400 to 1100 m 2 / g have been developed. These are disclosed in Patent Documents 1 to 3, for example.
触媒反応は表面反応であるので触媒の比表面積が大きいほど触媒活性が高い。また、触媒を担持するための担体は比表面積が大きいほど触媒活性を発現しやすい。このような観点から自動車用三元触媒をみると、支持体としてのモノリス成形体の比表面積が約0.2m2/g、吸着剤としてのアルミナ粒子の比表面積が110〜340m2/gであり、触媒の比表面積は粒径から20〜40m2/g程度であると推定される。したがって、従来の触媒粒子の粒径よりも1桁から2桁小さいナノサイズの触媒粒子を上記メソポーラス材料の細孔内に担持することによって触媒の表面積は従来の三元触媒の102〜104倍大きくなるので、これをモノリス成形体に塗布することによって自動車排ガスに対する触媒活性の向上を図ることが考えられ、この考えは、例えば、特許文献４〜７に開示されている。しかし、メソポーラス材料に触媒を担持しても、前記に述べたように担持触媒のシンタリングを完全に防止することはできなかった。その理由は、触媒自体の高温酸化性雰囲気での拡散移動を抑制するための工夫がなされていなかったからである。 Since the catalytic reaction is a surface reaction, the larger the specific surface area of the catalyst, the higher the catalytic activity. Further, the carrier for supporting the catalyst is more likely to exhibit the catalytic activity as the specific surface area is larger. From this point of view, looking at the three-way catalyst for automobiles, the specific surface area of the monolith molded body as the support is about 0.2 m 2 / g, and the specific surface area of the alumina particles as the adsorbent is 110 to 340 m 2 / g. The specific surface area of the catalyst is estimated to be about 20 to 40 m 2 / g from the particle size. Therefore, the surface area of the catalyst is 10 2 to 10 4 of the conventional three-way catalyst by supporting the nano-sized catalyst particles smaller by one to two digits than the particle diameter of the conventional catalyst particles in the pores of the mesoporous material. Since it becomes twice as large, it is conceivable to improve the catalytic activity with respect to automobile exhaust gas by applying it to a monolith molded body. This idea is disclosed in, for example, Patent Documents 4 to 7. However, even if the catalyst is supported on the mesoporous material, as described above, sintering of the supported catalyst cannot be completely prevented. The reason is that no contrivance has been made to suppress diffusion movement of the catalyst itself in a high-temperature oxidizing atmosphere.
即ち、上記従来技術では、触媒の高温時の耐酸化劣化性と高温時のシンタリング焼結防止のために耐熱性を向上させるには、耐熱性のある化合物で被覆すればこの問題だけは解決するが、本来の触媒活性が悪くなる相反する欠点があった。
本発明の目的は、上記の事情に鑑み、リーンバーン排ガスに含まれるＮＯｘの浄化のための新規な触媒を提供することである。具体的には、従来困難であったディーゼル排ＮＯｘ処理を長期間効率的に行うために、リーンバーンの比較的高濃度酸素雰囲気下での高温の排ＮＯｘに対しても高活性を維持してシンタリング焼結の欠点を同時に解決する新規の耐熱性触媒を提供することである。 In view of the above circumstances, an object of the present invention is to provide a novel catalyst for purifying NO x contained in lean burn exhaust gas. More specifically, in order to perform traditional which was difficult diesel exhaust NO x handle for a long time efficient, even maintaining a high activity to a high-temperature exhaust NO x at a relatively high concentration oxygen atmosphere in a lean burn Thus, it is an object of the present invention to provide a novel heat-resistant catalyst that simultaneously solves the drawbacks of sintering sintering.
本発明者は上記の目的を達成するために鋭意研究を重ねた結果、驚くべきことに、従来技術では、触媒の高温時の耐酸化劣化性と高温時のシンタリング焼結防止のための耐熱性を向上させるには、耐熱性のある化合物で被覆すればこの問題だけは解決するが、本来の触媒活性が悪くなり触媒活性を維持しようとすれば前記問題が解決しないという相反する欠点があったことを同時に解決し満足できることを見出した。本発明者は、耐熱性材料で表面を特定厚みで被覆した特定粒子径の白金含有触媒がリーンバーン排ＮＯｘ処理に対して非常に有効であり高温処理後においても触媒活性の低下が殆ど見られずシンタリング焼結もしないことを発見し、この知見に基づいて本発明を完成させるに至った。すなわち、本発明は、平均粒径0.3〜20ｎｍの白金含有触媒を耐熱性材料によって0.3〜10μｍの厚みで被覆し、これを排ＮＯｘ浄化用触媒として提供するものである。 As a result of intensive research to achieve the above-mentioned object, the inventor has surprisingly found that in the prior art, the catalyst is resistant to oxidation deterioration at high temperatures and heat resistance for preventing sintering sintering at high temperatures. In order to improve the properties, this problem can be solved only by coating with a heat-resistant compound, but there is a conflicting disadvantage that the original catalyst activity deteriorates and the problem cannot be solved if the catalyst activity is maintained. I found that I was able to solve this problem at the same time and be satisfied. The present inventor has also little decrease in the catalytic activity after a very an effective high-temperature processing specific particle size platinum-containing catalyst coated with a specific thickness of the surface with a heat-resistant material with respect to a lean-burn exhaust NO x treatment It was discovered that sintering was not performed, and the present invention was completed based on this finding. That is, the present invention is a platinum-containing catalyst having an average particle size of 0.3~20nm coated with heat-resistant material with a thickness of 0.3 to 10 [mu] m, it is to provide this as discharge the NO x purification catalyst.
本発明は、下記（１）から（５）の発明である。
（１）平均粒径０．３〜２０ｎｍの白金触媒自体を耐熱性材料によって０．３ｎｍ〜１０μｍの厚みで被覆した白金触媒がコアであり、耐熱性材料がシェルであるコア−シェル構造を持つことを特徴とする排ＮＯx浄化用触媒。
（２）耐熱性材料がシリカ、アルミナ、ジルコニア、チタニア、及びこれらの複合物であることを特徴とする前記（１）に記載の排ＮＯx浄化用触媒。
（３）白金粒子のコロイド分散液に耐熱性材料の前駆物質を溶解した溶液を混合することによって白金粒子の表面に耐熱性材料の前駆物質を吸着させた後、該前駆物質の加水分解
処理、熱処理を、上記記載の順に行って製造することを特徴とする前記（１）又は（２）に記載の排ＮＯx浄化用触媒の製造方法。
（４）前記（１）又は（２）に記載の排ＮＯx浄化用触媒を用いた、リッチバーンとリーンバーンを交互に行なうディーゼル用の排ＮＯx浄化用触媒。
（５）前記（１）又は（２）に記載の排ＮＯx浄化用媒を用いた、尿素供給システムを搭載するディーゼル用の排ＮＯx浄化用触媒。
The present invention is the following (1) to (5).
(1) A core-shell structure in which a platinum catalyst in which a platinum catalyst itself having an average particle size of 0.3 to 20 nm is coated with a heat resistant material in a thickness of 0.3 nm to 10 μm is a core, and the heat resistant material is a shell. discharging the NO x purification catalyst characterized by having.
(2) heat-resistant material is silica, alumina, zirconia, titania, and discharge the NO x purification catalyst according to (1), which is a composite thereof.
(3) After adsorbing the precursor of the heat-resistant material on the surface of the platinum particles by mixing a solution in which the precursor of the heat-resistant material is dissolved in the colloidal dispersion of platinum particles, the precursor is hydrolyzed. method for producing a discharge the NO x purification catalyst according to (1) or (2), characterized in that the heat treatment, to produce go in the order described above.
(4) (1) or (2) with discharge the NO x purification catalyst according to, discharge the NO x purification catalyst for diesel performing rich burn and the lean burn alternately.
(5) (1) or (2) with discharge the NO x purification for medium described, discharge the NO x purification catalyst for diesel mounting the urea supply system.
本発明の排ＮＯｘ浄化用触媒は、従来困難であったディーゼル排ＮＯｘ処理を長期間効率的に行うために、リーンバーンの比較的高濃度酸素雰囲気下での高温の排ＮＯｘに対しても高活性を維持してシンタリング焼結の欠点を同時に満足する新規の耐熱性触媒を提供することが出来る。例えば、三元触媒では酸素濃度14％の雰囲気下における一酸化窒素はほとんど浄化できないが、本発明のシリカで被覆した白金触媒は、酸素濃度14％の雰囲気に共存する一酸化窒素の80％以上を150〜300℃において浄化することができ、空気中750℃での熱処理後でも熱処理前の触媒の触媒活性と同程度の高活性を示した。 The exhaust NO x purification catalyst of the present invention is effective for high temperature exhaust NO x under a relatively high concentration oxygen atmosphere of lean burn in order to efficiently perform long-term diesel exhaust NO x treatment, which has been difficult in the past. However, it is possible to provide a novel heat-resistant catalyst that maintains high activity and satisfies the disadvantages of sintering sintering at the same time. For example, a three-way catalyst can hardly purify nitrogen monoxide in an atmosphere with an oxygen concentration of 14%, but the platinum catalyst coated with silica of the present invention is 80% or more of nitrogen monoxide coexisting in an atmosphere with an oxygen concentration of 14%. Was able to be purified at 150 to 300 ° C., and even after heat treatment at 750 ° C. in air, high activity comparable to that of the catalyst before heat treatment was exhibited.
以下、本発明を詳細に説明する。
本発明の第1の特徴は、白金含有触媒を耐熱性材料で被覆していることである。ディーゼルエンジンの排ガス温度は、通常、700℃以下であるので、還元性雰囲気下では主触媒である白金粒子がシンタリングする恐れは殆どないが、触媒表面に吸着したイオウ分等の被毒物質を除去するために酸化雰囲気中750〜850℃で熱処理を行った場合には、白金は酸素によって一度低融点の酸化物に酸化されるのでシンタリングが起きる。これは、従来の三元触媒についても同様である。シンタリングを防止するために、通常、高融点物質との合金化が考えられるが、白金は合金化が困難である。そこで、シンタリング防止のための方策を鋭意検討した結果、白金自体を耐熱性材料で被覆すると非常に効果的であることがわかった。
Hereinafter, the present invention will be described in detail.
The first feature of the present invention is that the platinum-containing catalyst is coated with a heat-resistant material. Since the exhaust gas temperature of a diesel engine is usually 700 ° C. or less, there is almost no risk that the main catalyst platinum particles will sinter in a reducing atmosphere, but poisonous substances such as sulfur adsorbed on the catalyst surface will be removed. When heat treatment is performed at 750 to 850 ° C. in an oxidizing atmosphere for removal, sintering occurs because platinum is once oxidized to a low melting point oxide by oxygen. The same applies to the conventional three-way catalyst. In order to prevent sintering, alloying with a high melting point material is usually considered, but platinum is difficult to alloy. Therefore, as a result of intensive studies on measures for preventing sintering, it was found that it is very effective to coat platinum itself with a heat-resistant material.
本発明における耐熱性材料は、その目的から大気中で1000℃以上の融点をもつ材料であれば、それが主触媒である白金の触媒毒でない限りは使用できる。このような材料として、例えば、ホウ素、炭素、珪素、チタン、ジルコニウム、ハフニウム、バナジウム、ニオブ、タンタル、クロム、モリブデン、タングステン、マンガン、レニウム、鉄、ルテニウム、コバルト、ロジウム、イリジウム、ニッケル、銅、スカンジウム、イットリウム、ガドリニウム、等の元素、及びこれらの酸化物、硫化物、窒化物、炭化物、珪化物、ホウ化物、酸化セリウム（セリア）、酸化錫、酸化バリウム、酸化亜鉛、酸化アルミニウム（アルミナ）、酸化カルシウム（カルシア）、酸化マグネシウム（マグネシア）、酸化ランタン、各種のゼオライト、モノリス成形体の原料であるコージェライト、等が挙げられる。これらの中で、シリカ、アルミナ、ジルコニア、チタニア、及びこれらの複合物は主触媒のシンタリング抑制効果が高いので好ましい。 The heat-resistant material in the present invention can be used as long as it is a material having a melting point of 1000 ° C. or higher in the atmosphere for the purpose as long as it is not a catalyst poison of platinum as a main catalyst. Examples of such materials include boron, carbon, silicon, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel, copper, Elements such as scandium, yttrium, gadolinium, and their oxides, sulfides, nitrides, carbides, silicides, borides, cerium oxide (ceria), tin oxide, barium oxide, zinc oxide, aluminum oxide (alumina) , Calcium oxide (calcia), magnesium oxide (magnesia), lanthanum oxide, various zeolites, cordierite which is a raw material of a monolith molded body, and the like. Among these, silica, alumina, zirconia, titania, and a composite thereof are preferable because they have a high sintering suppressing effect on the main catalyst.
本発明の耐熱性材料による被覆は、被覆層の厚みが厚すぎる場合には排ガスの透過性及び拡散性が低いので主触媒の活性低下が起き、又、薄すぎる場合には触媒の熱膨張によって破壊し易い。したがって、被膜の厚みは経験的に求める必要があった。実験によって求められた好ましい厚みは耐熱性材料の種類に依存するので一定値ではないが、通常、0.3ｎｍ〜10μｍの範囲が好ましい。緻密な構造を有するアルミナ、ジルコニア等では0.3〜50ｎｍの範囲であればよいが、構造的空隙を多く持つシリカ、メソポーラス材料、各種のゼオライト、コージェライト等では、1μｍの厚みでも排ガスの透過性がよい。
本発明の耐熱性材料で被覆した白金含有触媒は、コア-シェル構造の金属微粒子を製造するために開発された公知の方法、例えば、既に引用文献として挙げた非特許文献1〜9に記載の方法を応用することによって製造することができる。例えば、白金粒子のコロイド分散液と耐熱性材料の前駆物質を溶解した溶液を混合することによって白金粒子の表面に耐熱性材料の前駆物質を吸着させた後、前駆物質の加水分解処理、酸化還元処理、熱処理等の所要の反応操作を行って製造することができる。あるいは、白金粒子のコロイド分散液を濃縮して得たゲル状物質を耐熱性材料の前駆物質を溶解した溶液に加えることによって白金粒子の表面に耐熱性材料の前駆物質を吸着させた後、溶液を濾過、所定時間放置することによって前駆物質を加水分解させた後、濾過、酸化還元処理、熱処理等の所要の反応操作を行って製造することもできる。
In the coating with the heat-resistant material of the present invention, when the coating layer is too thick, the exhaust gas permeability and diffusivity are low, so that the activity of the main catalyst is reduced. Easy to destroy. Therefore, the thickness of the coating had to be determined empirically. The preferable thickness obtained by experiment depends on the kind of the heat-resistant material and is not a constant value, but is usually preferably in the range of 0.3 nm to 10 μm. In the case of alumina, zirconia, etc. having a dense structure, it may be in the range of 0.3 to 50 nm, but in the case of silica having many structural voids, mesoporous materials, various zeolites, cordierite, etc., the permeability of exhaust gas is 1 μm thick. Good.
The platinum-containing catalyst coated with the heat-resistant material of the present invention is a known method developed for producing core-shell structured metal fine particles, for example, as described in Non-Patent Documents 1 to 9 already cited as cited references. It can be manufactured by applying the method. For example, by mixing a colloidal dispersion of platinum particles and a solution in which a precursor of a heat resistant material is dissolved, the precursor of the heat resistant material is adsorbed on the surface of the platinum particles, and then the precursor is hydrolyzed and redox. It can be produced by performing a required reaction operation such as treatment or heat treatment. Alternatively, the gel-like substance obtained by concentrating the colloidal dispersion of platinum particles is added to a solution in which the precursor of the heat-resistant material is dissolved to adsorb the precursor of the heat-resistant material on the surface of the platinum particle, and then the solution The precursor can be hydrolyzed by filtering and allowing to stand for a predetermined time, and then subjected to necessary reaction operations such as filtration, redox treatment, and heat treatment.
他の方法としては、メソポーラス材料の製造方法として開示されている公知の方法、例えば、引用文献として挙げた特許文献1、2、及び3の方法を応用して製造することができる。この方法では、白金の前駆物質を溶解した水溶液又は白金のコロイド分散液に界面活性剤を加えて白金の前駆物質に界面活性剤を吸着させ、これに耐熱性材料の前駆物質を加えて反応させることによって耐熱性材料の皮膜を形成させる。耐熱性材料の前駆物質には、通常、金属アルコキシドを用いる。
界面活性剤は、従来のメソポア分子ふるいの作成に用いられているミセル形成の界面活性剤、例えば、長鎖の4級アンモニウム塩、長鎖のアルキルアミンＮ−オキシド、長鎖のスルホン酸塩、ポリエチレングリコールアルキルエーテル、ポリエチレングリコール脂肪酸エステル等のいずれであってもよい。溶媒として、通常、水、アルコール類、ジオールの１種以上が用いられるが、有機溶媒が好ましい。反応系に金属への配位能を有する化合物を少量添加すると反応系の安定性を著しく高めることができる。このような安定剤としては、アセチルアセトン、テトラメレンジアミン、エチレンジアミン四酢酸、ピリジン、ピコリンなどの金属配位能を有する化合物が好ましい。
As other methods, a known method disclosed as a method for producing a mesoporous material, for example, the methods of Patent Documents 1, 2, and 3 cited as cited documents can be applied for production. In this method, a surfactant is added to an aqueous solution in which a platinum precursor is dissolved or a colloidal dispersion of platinum, the surfactant is adsorbed on the platinum precursor, and a precursor of a heat-resistant material is added thereto for reaction. As a result, a film of a heat-resistant material is formed. Usually, a metal alkoxide is used as a precursor of the heat-resistant material.
Surfactants include micelle-forming surfactants used to make conventional mesopore molecular sieves, such as long-chain quaternary ammonium salts, long-chain alkylamine N-oxides, long-chain sulfonates, Any of polyethylene glycol alkyl ether, polyethylene glycol fatty acid ester and the like may be used. As the solvent, one or more of water, alcohols, and diols are usually used, and an organic solvent is preferable. When a small amount of a compound having a coordination ability to metal is added to the reaction system, the stability of the reaction system can be remarkably enhanced. As such a stabilizer, a compound having a metal coordination ability such as acetylacetone, tetramethylenediamine, ethylenediaminetetraacetic acid, pyridine, and picoline is preferable.
白金の前駆物質、耐熱性材料の前駆物質、界面活性剤、溶媒及び安定剤からなる反応系の組成は、白金の前駆物質／耐熱性材料の前駆物質のモル比が0.1〜100、好ましくは1〜10、白金の前駆物質/界面活性剤のモル比が1〜30、好ましくは1〜10、溶媒/界面活性剤のモル比が1〜1000、好ましくは5〜500、安定剤/白金の前駆物質のモル比が0.01〜1.0、好ましくは0.2〜0.6である。反応温度は、20〜180℃、好ましくは20〜100℃の範囲である。反応時間は5〜100時間、好ましくは10〜50時間の範囲である。反応生成物は通常、濾過により分離し、十分に水洗後、乾燥し、次いで、含有している界面活性剤をアルコールなどの有機溶媒により抽出後、空気中500〜1000℃で完全に熱分解した後、水素等の還元雰囲気中500〜1000℃で数時間還元処理することに耐熱性材料で被覆された白金触媒を得ることができる。 The composition of the reaction system consisting of platinum precursor, heat-resistant material precursor, surfactant, solvent and stabilizer has a molar ratio of platinum precursor / heat-resistant material precursor of 0.1 to 100, preferably 1. ~ 10, platinum precursor / surfactant molar ratio 1-30, preferably 1-10, solvent / surfactant molar ratio 1-1000, preferably 5-500, stabilizer / platinum precursor The molar ratio of the substances is 0.01 to 1.0, preferably 0.2 to 0.6. The reaction temperature is in the range of 20 to 180 ° C, preferably 20 to 100 ° C. The reaction time ranges from 5 to 100 hours, preferably from 10 to 50 hours. The reaction product is usually separated by filtration, thoroughly washed with water and dried, and then the contained surfactant is extracted with an organic solvent such as alcohol and then completely pyrolyzed at 500 to 1000 ° C. in air. Thereafter, a platinum catalyst coated with a heat-resistant material can be obtained by performing a reduction treatment at 500 to 1000 ° C. for several hours in a reducing atmosphere such as hydrogen.
耐熱性材料の被覆層の厚みは、反応処理操作時における耐熱性材料の前駆物質の濃度、加水分解時間、酸化還元処理時間等によって任意に調節することができる。白金粒子のコロイド分散液の製造は、通常、白金前駆物質と所要の還元物質を含む水溶液に親水性の高分子材料を加えて加熱することによる公知の方法によって製造することができる。この方法では、白金のナノ粒子が高分子材料でマイクロカプセル化されたコロイド分散液として得られる。白金前駆物質としては、例えば、H2PtCl4、(NH4)2PtCl4、H2PtCl6、(NH4)2PtCl6、Pt(NH3)4(NO3)2、Pt(NH3)4(OH)2、PtCl4、白金のアセチルアセトナート、等を用いることができる。 The thickness of the coating layer of the heat resistant material can be arbitrarily adjusted by the concentration of the precursor of the heat resistant material during the reaction treatment operation, the hydrolysis time, the oxidation-reduction treatment time, and the like. The colloidal dispersion of platinum particles can be usually produced by a known method in which a hydrophilic polymer material is added to an aqueous solution containing a platinum precursor and a required reducing substance and heated. In this method, platinum nanoparticles are obtained as a colloidal dispersion liquid microencapsulated with a polymer material. Examples of the platinum precursor include H 2 PtCl 4 , (NH 4 ) 2 PtCl 4 , H 2 PtCl 6 , (NH 4 ) 2 PtCl 6 , Pt (NH 3 ) 4 (NO 3 ) 2 , Pt (NH 3 ) 4 (OH) 2 , PtCl 4 , platinum acetylacetonate, and the like can be used.
還元剤としては、アルコール、酒石酸塩、シュウ酸、各種の水素化物、ホルマリン、ヒドラジン等の一般的に用いられる還元剤を用いることができる。高分子材料としては、ポリビニルピロリドン、ポリビニルアルコール、ポリ酢酸ビニル、ポリエチレングリコール、ポリアクリル酸、アルギン酸塩、尿素樹脂、アラビアゴム、各種のゴムラテックス等の一般的に用いられる水溶性高分子材料を用いることができる。必要に応じて主触媒に添加する助触媒的成分の原料としては、例えば、塩化物、硝酸塩、硫酸塩、炭酸塩、酢酸塩などの水溶性塩類を用いることができる。これらの原料を白金の前駆物質に混合して同様にして製造することができる。 As the reducing agent, commonly used reducing agents such as alcohol, tartrate, oxalic acid, various hydrides, formalin and hydrazine can be used. As the polymer material, commonly used water-soluble polymer materials such as polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl acetate, polyethylene glycol, polyacrylic acid, alginate, urea resin, gum arabic, and various rubber latexes are used. be able to. As a raw material of the co-catalytic component added to the main catalyst as necessary, for example, water-soluble salts such as chloride, nitrate, sulfate, carbonate and acetate can be used. These raw materials can be mixed with a platinum precursor and manufactured in the same manner.
また、耐熱性材料の前駆物質としては、例えば、ホウ素、炭素、珪素、チタン、ジルコニウム、アルミニウム、セリウム、ハフニウム、バナジウム、ニオブ、タンタル、クロム、モリブデン、タングステン、マンガン、レニウム、鉄、ルテニウム、コバルト、ロジウム、イリジウム、ニッケル、銅、スカンジウム、イットリウム、ガドリニウム、等の水溶性塩化物、硝酸塩、硫酸塩、炭酸塩、酢酸塩、アンモニア錯体、アルコキシド、等を用いることができる。通常、有機溶媒に可溶のアルコキシド、水溶性の塩化物、硝酸塩、硫酸塩、炭酸塩、酢酸塩、アンモニア錯体、等が用いられる。上記方法において、白金の前駆物質/耐熱性材料の前駆物質のモル比は通常0.01〜100、好ましくは0.1〜10である。 Examples of precursors for heat-resistant materials include boron, carbon, silicon, titanium, zirconium, aluminum, cerium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, iron, ruthenium, and cobalt. Water-soluble chlorides such as rhodium, iridium, nickel, copper, scandium, yttrium, and gadolinium, nitrates, sulfates, carbonates, acetates, ammonia complexes, alkoxides, and the like can be used. Usually, alkoxides soluble in organic solvents, water-soluble chlorides, nitrates, sulfates, carbonates, acetates, ammonia complexes, and the like are used. In the above method, the molar ratio of the precursor of platinum / precursor of the heat-resistant material is usually 0.01 to 100, preferably 0.1 to 10.
本発明の第2の特徴は、主触媒が白金であることである。従来、白金を含有する自動車排ガス処理用触媒としては三元触媒が知られているが、この触媒はディーゼル排ＮＯｘ浄化処理にはほとんど効果がないことが知られている。その理由は、白金以外の構成元素であるパラジウム及びロジウムが低濃度の酸素によって表面酸化を受けるためである。三元触媒は白金-パラジウム-ロジウムで構成されているので表面酸化を受けるとたちまち失活し易い。本発明で白金を主触媒として用いる理由は、白金が排ＮＯｘの主成分である一酸化窒素を共存酸素によって二酸化窒素に酸化する触媒能力が高く、高温の酸素雰囲気中でも一度は酸化物になるがすぐに分解して白金に戻るので、化学的に安定であるからである。 The second feature of the present invention is that the main catalyst is platinum. Conventionally, the three-way catalyst has been known as automobile exhaust gas treatment catalyst containing platinum, the catalyst is known to have little effect on diesel exhaust the NO x purification process. The reason is that palladium and rhodium, which are constituent elements other than platinum, undergo surface oxidation by a low concentration of oxygen. Since the three-way catalyst is composed of platinum-palladium-rhodium, it is easily deactivated when subjected to surface oxidation. The reason for using platinum as a main catalyst in the present invention, platinum high catalytic ability to oxidize to nitrogen dioxide to nitric oxide which is a main component of the exhaust NO x by coexisting oxygen, becomes an oxide once even during hot oxygen atmosphere Is decomposed immediately to platinum, and is chemically stable.
触媒反応によって生成する二酸化窒素は、ディーゼル燃料に少量含まれる炭素数1〜6の低級オレフィン及び低級パラフィン又はトラックなどに搭載できる尿素態アンモニアなどの還元性物質によって容易に窒素と水に分解される。
触媒粒子の表面積は粒径の二乗に反比例するので、触媒粒子が小さいほど触媒活性が高くなる。例えば、1ｎｍの触媒粒子の表面積は0.1μｍのそれと比べると104倍大きい。また、ナノサイズに微粒化された触媒粒子は、活性を示すテラス、エッジ、コーナー、ステップなどの結晶面を多量にもつので、触媒活性が著しく向上するだけでなく、バルクでは触媒活性を示さないような不活性金属でも予期しなかったような触媒活性を発現する場合があることが知られている。したがって、触媒能力の観点からは触媒粒子は細かいほど好ましいのであるが、反面、微粒化による表面酸化、副反応などの好ましくない性質もでてくるので、触媒粒子の粒径には最適範囲が存在する。本発明における目的のＮＯｘ分解浄化処理に対して効果的な活性を示す触媒粒子の直径は0.3〜20ｎｍの範囲にあり、特に1〜10ｎｍの範囲が高活性を示すことがわかった。
Nitrogen dioxide produced by catalytic reaction is easily decomposed into nitrogen and water by reducing substances such as urea ammonia that can be mounted on lower olefins and lower paraffins or trucks with 1 to 6 carbon atoms contained in a small amount of diesel fuel. .
Since the surface area of the catalyst particles is inversely proportional to the square of the particle diameter, the smaller the catalyst particles, the higher the catalytic activity. For example, the surface area of the catalyst particles of 1nm is 10 4 times greater than that of 0.1 [mu] m. In addition, nano-sized catalyst particles have a large number of crystal surfaces such as terraces, edges, corners, steps, etc. that show activity, so that not only catalytic activity is significantly improved but also catalytic activity is not shown in bulk. It is known that such an inert metal may exhibit unexpected catalytic activity. Therefore, finer catalyst particles are preferable from the viewpoint of catalytic ability, but on the other hand, there are also undesirable properties such as surface oxidation and side reactions due to atomization, so there is an optimum range for the particle size of the catalyst particles. To do. It has been found that the diameter of the catalyst particles exhibiting an effective activity for the target NO x decomposition and purification treatment in the present invention is in the range of 0.3 to 20 nm, and particularly in the range of 1 to 10 nm is high activity.
本発明の主触媒である白金に異なる機能を持つ助触媒的成分を添加することによってシナジー効果による触媒性能の向上をはかることもできる。このような成分として、例えば、クロム、マンガン、鉄、コバルト、ニッケル、銅、亜鉛、バリウム、スカンジウム、イットリウム、チタン、ジルコニウム、ハフニウム、ニオブ、タンタル、モリブデン、タングステン、ランタン、セリウム、バリウム、ロジウム、レニウム、及びこれらの化合物を挙げることができる。これらの中で、不動態化膜になるクロム、鉄、コバルト、ニッケル、還元剤の吸着力が比較的高い銅、ＮＯｘ吸蔵性がある酸化バリウム等のアルカリ土類酸化物、中程度の酸化力を持つ酸化セリウムと三二酸化マンガン、高酸化力を持つテトラオキソ鉄(VI)酸バリウム、ＳＯｘ被毒防止に有効な銅-亜鉛、鉄-クロム、酸化モリブデンなどは好ましい。この成分の添加量は、通常、主触媒と同質量程度から100倍程度又は100分の1程度であるが、必要に応じてこの範囲外であってもよい。 By adding a promoter component having a different function to platinum which is the main catalyst of the present invention, the catalyst performance can be improved by a synergistic effect. Examples of such components include chromium, manganese, iron, cobalt, nickel, copper, zinc, barium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, lanthanum, cerium, barium, rhodium, Mention may be made of rhenium and their compounds. Among them, chromium becomes passivation film, iron, cobalt, nickel, suction force is relatively high copper, alkaline earth oxides such as barium oxide there is the NO x storage of the reducing agent, the moderate oxidation cerium oxide and the three manganese dioxide with the power, tetraoxo iron (VI) barium with high oxidizing power, effective copper SO x poisoning prevention - zinc, iron - chromium, molybdenum oxide is preferable. The addition amount of this component is usually about the same mass as the main catalyst, about 100 times, or about 1/100, but may be outside this range if necessary.
本発明の触媒は、耐熱性材料で被覆した触媒だけで用いることができるが、触媒分散用の媒体と混合して用いることもできる。媒体の種類は触媒の活性を妨害するような材料でなければよい。通常、従来の活性アルミナ、各種のゼオライトやコージェライトの他にメソポーラス材料、例えば、メソポーラスシリカ、アルミナ、ジルコニア、チタニア、セリア、イットリア、ニオビア、メタロシリケート、及びこれらの複合物を挙げることができる。媒体と白金主触媒の混合は、通常、白金の含有率が0.1〜20質量％の範囲になるように混合するのであるが、好ましくは0.1〜10質量％であり、量的な問題がなければ、通常は、数％の含有率で用いる。触媒の含有率は20質量％以上でも可能であるが、含有率が過剰になると触媒の分散性が低下するのでよくない。また、0.1質量％未満では活性が十分ではない。 The catalyst of the present invention can be used only with a catalyst coated with a heat-resistant material, but can also be used by mixing with a catalyst dispersion medium. The type of medium should not be a material that interferes with the activity of the catalyst. Usually, in addition to conventional activated alumina, various zeolites and cordierite, mesoporous materials such as mesoporous silica, alumina, zirconia, titania, ceria, yttria, niobia, metallosilicate, and composites thereof can be mentioned. The medium and the platinum main catalyst are usually mixed so that the platinum content is in the range of 0.1 to 20% by mass, preferably 0.1 to 10% by mass, and there is no quantitative problem. Usually, it is used at a content of several percent. The content of the catalyst can be 20% by mass or more, but if the content is excessive, the dispersibility of the catalyst is lowered, which is not good. Moreover, if it is less than 0.1 mass%, activity is not enough.
本発明触媒と触媒分散用媒体とが混合された触媒の製造方法は、従来の方法を応用して所要の触媒を製造することがきる。例えば、分散用媒体に本発明触媒の分散液を吸収させるか又は本発明触媒の分散液に分散用媒体を浸漬後、乾燥させた後、必要に応じて不活性気流中高温処理することに製造することができる。
また、本発明触媒を自動車用排ＮＯｘ浄化用触媒として用いる場合には、通常、モノリス成形体に触媒を塗布して用いる。ここでいうモノリス成形体とは、成形体の断面が網目状で、軸方向に平行に互いに薄い壁によって仕切られたガス流路を設けている成形体のことである。成形体の外形は、通常は、円柱形である。本発明触媒の塗布量は、3〜30質量％が好ましい。30％を超える塗布は、触媒へのガス拡散が遅いので好ましくない。また、3％以下では触媒性能が十分ではない。モノリス成形体への白金の塗布量相当の付着量は、成形体の0.03〜3質量％が好ましい。
The method for producing a catalyst in which the catalyst of the present invention and the catalyst dispersion medium are mixed can produce a required catalyst by applying a conventional method. For example, the dispersion medium of the present invention is absorbed in the dispersion medium, or the dispersion medium is immersed in the dispersion liquid of the present invention, dried, and then subjected to high temperature treatment in an inert gas flow as necessary. can do.
In the case of using the present invention catalyst as exhaust the NO x purification catalyst for automobiles, usually, used catalyst was applied to the monolithic molding. The monolith molded body as used herein refers to a molded body in which the cross section of the molded body is mesh-shaped and provided with gas flow paths partitioned by thin walls parallel to each other in the axial direction. The outer shape of the molded body is usually a cylindrical shape. The coating amount of the catalyst of the present invention is preferably 3 to 30% by mass. Application exceeding 30% is not preferable because gas diffusion to the catalyst is slow. Moreover, if it is 3% or less, the catalyst performance is not sufficient. The adhesion amount corresponding to the coating amount of platinum on the monolith molded body is preferably 0.03 to 3% by mass of the molded body.
本発明触媒を塗布したモノリス成形体の製造は、自動車用三元触媒を付着したモノリス成形体の製造方法に準じて行うことができる。例えば、耐熱性材料で被覆した白金触媒とバインダーとしてのコロイダルシリカを、通常、1：（0.01〜0.2）の質量割合で混合した混合物をつくり、これを水分散することによって通常10〜50質量％のスラリーを調整した後、該スラリーに上記記載のモノリス成形体と同様の構造を有するモノリス成形体を浸漬してモノリス成形体のガス流路の内壁にスラリーを付着させ、乾燥後、窒素、ヘリウム、アルゴンなどの不活性雰囲気下500〜1000℃で数時間熱処理することによって製造することがきる。コロイダルシリカ以外のバインダーとしては、メチルセルロース、アクリル樹脂、ポリエチレングリコール、アラビアゴム、各種のゴムラテックスなどを適宜用いることもできる。他の方法としては、モノリス成形体に触媒の前駆物質を含浸し、還元処理、熱処理を行った後、耐熱性材料で被覆する方法によっても製造することができる。 Manufacture of the monolith molded object which apply | coated this invention catalyst can be performed according to the manufacturing method of the monolith molded object which adhered the three-way catalyst for motor vehicles. For example, a platinum catalyst coated with a heat-resistant material and colloidal silica as a binder are usually mixed at a mass ratio of 1: (0.01 to 0.2), and then 10 to 50% by mass by dispersing this in water. Then, a monolith molded body having the same structure as the monolith molded body described above is immersed in the slurry to adhere the slurry to the inner wall of the gas flow path of the monolith molded body, and after drying, nitrogen, helium It can be produced by heat treatment at 500 to 1000 ° C. for several hours under an inert atmosphere such as argon. As binders other than colloidal silica, methyl cellulose, acrylic resin, polyethylene glycol, gum arabic, various rubber latexes, and the like can be used as appropriate. As another method, it can also be produced by a method in which a monolith molded body is impregnated with a catalyst precursor, subjected to reduction treatment and heat treatment, and then coated with a heat resistant material.
成形体に塗布した本発明触媒の厚みは、通常、1μｍ〜100μｍであるのが好ましく、10μｍ〜50μｍの範囲が特に好ましい。100μｍを超えると反応ガスの拡散が遅くなるのでよくない。1μm未満では、触媒性能の劣化が早いのでよくない。
本発明触媒は、自動車、特にディーゼル自動車に搭載することによって、自動車が排出するリーンバーン排ＮＯｘを150〜700℃の広い温度範囲において極めて効果的に浄化することができる。排ＮＯｘの処理には還元剤が必要であるが、乗用車などの小型車の場合には、燃料である軽油に少量含まれている炭素数１から６の低級オレフィン及び低級パラフィンが還元剤となるので、燃料を直接又は改質器を通して触媒上に供給すればよい。
In general, the thickness of the catalyst of the present invention applied to the molded body is preferably 1 μm to 100 μm, and particularly preferably in the range of 10 μm to 50 μm. If it exceeds 100 μm, the diffusion of the reaction gas becomes slow, which is not good. If it is less than 1 μm, the catalyst performance deteriorates quickly, which is not good.
The present invention catalyst is an automobile, in particular by mounting the diesel automobile can car purifying very effectively in a wide temperature range of 150 to 700 ° C. The lean burn exhaust NO x to be discharged. Although the processing of the exhaust NO x is required reducing agent, in the case of small vehicles, such as passenger cars, lower olefins and lower paraffins with carbon atoms of 1 contained a small amount in light oil which is fuel 6 is a reducing agent Therefore, the fuel may be supplied onto the catalyst directly or through the reformer.
リッチバーンの時には酸素濃度が高くリーンバーンの時には酸素濃度が低いので、リッチバーンとリーンバーンを交互に行うことができる小型ディーゼルの排ガス浄化処理のために本発明の触媒を用いると、150〜700℃の広い温度範囲において効率よく排ＮＯｘを浄化処理できる。また、トラックなどの大型車の場合には、通常、尿素水を熱分解して還元剤としてのアンモニアを発生させ触媒上に供給するシステムを利用できるので、尿素供給システムを搭載する大型ディーゼル用の排ＮＯｘ浄化用触媒としても用いることができる。 Since the oxygen concentration is high during the rich burn and the oxygen concentration is low during the lean burn, when the catalyst of the present invention is used for exhaust gas purification treatment of a small diesel engine capable of alternately performing rich burn and lean burn, 150 to 700 efficiently exhaust NO x can be purified processed in wide temperature range of ° C.. Also, in the case of large vehicles such as trucks, it is usually possible to use a system that thermally decomposes urea water to generate ammonia as a reducing agent and supplies it onto the catalyst. it can also be used as discharge the NO x purification catalyst.
以下に実施例などを挙げて本発明を具体的に説明する。
実施例中の粉末Ｘ線回折パターンは理学電機社製RINT2000型Ｘ線回折装置によって測定した。触媒の平均粒径及び高融点材料の被膜の厚みは、粉末Ｘ線回折パターンのメインピークの半値幅をシェラー式に代入して算出した。比表面積及び細孔分布は、脱吸着の気体として窒素を用い、カルロエルバ社製ソープトマチック1800型装置によって測定した。比表面積はＢＥＴ法によって求めた。細孔分布は1〜200nmの範囲を測定し、ＢＪＨ法で求められる微分分布で示した。合成した担体の多くは指数関数的に左肩上がりの分布における特定の細孔直径の位置にピークを示した。このピークを、便宜上、細孔ピークと呼ぶ。材料の結晶性と残留界面活性剤を調べるための熱分析は、島津製作所製DTA-50型熱分析装置によって、昇温速度20℃min-1で測定した。自動車排ＮＯｘのモデルガスとして、ヘリウム希釈一酸化窒素、酸素、及び還元性ガス（エチレン又はアンモニア）を用いた。処理後のガスに含まれるＮＯｘの含有量は、以下の亜鉛還元ナフチルエチレンジアミン法（JIS K 0104）に準じて定量分析し、一酸化窒素の処理率を求めた。[操作方法]テドラーバッグに反応ガスを採取する。反応ガスの入ったテドラーバッグにガスタイトシリンジを差込み反応ガスを20 ml採取する。三方コックを付けた容量100mlのナスフラスコ内を減圧にし、ガスタイトシリンジの反応ガスを全量導入する。該ナスフラスコに0.1規定アンモニア水20mlを加え１時間放置する。１０％塩酸水溶液にスルファニルアミド１ｇを溶解した溶液を１ml加え、３０秒程度攪拌後、３分放置する。これに、蒸留水100mlにN-（１-ナフチル）エチレンジアミン二塩酸塩0.1ｇを溶解した溶液を1ml加え、30秒程度攪拌後、20分静置する。この液を石英セル（セル長10mm）に入れ、540nmの吸光度を測定する。
The present invention will be specifically described below with reference to examples.
The powder X-ray diffraction patterns in the examples were measured with a RINT2000 type X-ray diffraction apparatus manufactured by Rigaku Corporation. The average particle diameter of the catalyst and the film thickness of the high melting point material were calculated by substituting the half width of the main peak of the powder X-ray diffraction pattern into the Scherrer equation. The specific surface area and pore distribution were measured with a Sorpmatic 1800 type apparatus manufactured by Carlo Elba using nitrogen as a desorption gas. The specific surface area was determined by the BET method. The pore distribution was measured in the range of 1 to 200 nm and indicated by a differential distribution obtained by the BJH method. Many of the synthesized carriers showed a peak at a specific pore diameter in an exponentially increasing distribution. This peak is called a pore peak for convenience. Thermal analysis for investigating the crystallinity of the material and the residual surfactant was measured with a DTA-50 type thermal analyzer manufactured by Shimadzu Corporation at a heating rate of 20 ° C. min −1 . As a model gas of a motor vehicle exhaust NO x, helium dilution monoxide nitrogen, oxygen, and a reducing gas (ethylene or ammonia) was used. The content of NO x contained in the treated gas was quantitatively analyzed according to the following zinc-reduced naphthylethylenediamine method (JIS K 0104) to determine the treatment rate of nitric oxide. [Operation method] Collect the reaction gas in the Tedlar bag. Insert a gas tight syringe into the Tedlar bag containing the reaction gas and collect 20 ml of the reaction gas. The inside of the eggplant flask having a capacity of 100 ml with a three-way cock is evacuated, and the reaction gas in the gas tight syringe is introduced in its entirety. Add 20 ml of 0.1N ammonia water to the eggplant flask and leave for 1 hour. Add 1 ml of a solution of 1 g of sulfanilamide in a 10% aqueous hydrochloric acid solution, stir for about 30 seconds and let stand for 3 minutes. To this, 1 ml of a solution obtained by dissolving 0.1 g of N- (1-naphthyl) ethylenediamine dihydrochloride in 100 ml of distilled water is added, stirred for about 30 seconds, and allowed to stand for 20 minutes. This solution is put into a quartz cell (cell length: 10 mm), and the absorbance at 540 nm is measured.
一酸化窒素の反応率は、下式（１）より求める。
「比較例１」比較サンプル
市販の白金担持触媒〔日揮化学株式会社製造：白金の担持量が2質量％、担体がγ-アルミナ（粒径2〜3μｍの微粒子）〕を、従来の白金触媒に模した触媒として比較実験に用いた。
"Comparative example 1" comparative sample A commercially available platinum-supported catalyst (manufactured by JGC Chemical Co., Ltd .: platinum loading is 2% by mass, carrier is γ-alumina (fine particles with a particle size of 2 to 3 μm)) The simulated catalyst was used in a comparative experiment.
「実施例１」シリカ被覆白金触媒の合成
ビーカーに、市販の白金コロイド分散液（田中貴金属製：白金の平均粒径約2ｎｍ、白金の含有率4質量％）50ｇ、及びエタノール100ｇを入れ、攪拌下でテトラエトキシシラン40ｇを加えて室温で22時間攪拌した。生成物を遠心分離した後、沈殿物をエタノールに再分散した。エタノールに分散したコロイド粒子は白金粒子がシリカの前駆体（部分的に脱水縮合したエトキシ基を含むシロキサン結合物質）で被覆された微粒子であったので、これに少量の水を加えて未反応のエトキシ基を加水分解し、続いてアセトンを過剰量加えて生成物を沈降させ、該沈殿物を空気中７５０℃で３時間熱処理することによって、シリカで被覆された白金微粒子が得られることがわかった。該白金微粒子におけるシリカ膜の厚みは約10ｎｍであった。したがって、上記で調整したコロイド粒子のエタノール分散液を、適当量だけスポイトで取り、市販のシリカ微粒子（平均粒径2μｍのシリカ粉末）に加え、混合、乾燥後、ヘリウム希釈水素（10ｖ/ｖ％）気流下750℃3時間熱処理して、シリカに分散した触媒を得た。白金の含有率は2質量％であった。
[Example 1] Synthesis of silica-coated platinum catalyst In a beaker, 50 g of a commercially available platinum colloid dispersion (Tanaka Kikinzoku: average platinum particle size of about 2 nm, platinum content of 4% by mass) and 100 g of ethanol were added and stirred. Below, 40 g of tetraethoxysilane was added and stirred at room temperature for 22 hours. After centrifuging the product, the precipitate was redispersed in ethanol. The colloidal particles dispersed in ethanol were fine particles in which platinum particles were coated with a silica precursor (a siloxane-bonded substance containing partially dehydrated and condensed ethoxy groups). It was found that platinum fine particles coated with silica can be obtained by hydrolyzing the ethoxy group, followed by adding acetone in excess to precipitate the product, and heat treating the precipitate in air at 750 ° C. for 3 hours. It was. The thickness of the silica film in the platinum fine particles was about 10 nm. Therefore, an appropriate amount of the ethanol dispersion of colloidal particles prepared above is taken with a dropper, added to commercially available silica fine particles (silica powder with an average particle diameter of 2 μm), mixed, dried, and diluted with helium (10 v / v%). ) Heat treatment was performed at 750 ° C. for 3 hours in an air stream to obtain a catalyst dispersed in silica. The platinum content was 2% by mass.
「実施例２」アルミナ被覆白金触媒の合成
ビーカーに、市販の白金コロイド分散液（田中貴金属製：白金の平均粒径約2ｎｍ、白金の含有率4質量％）50ｇ、及びエタノール100ｇを入れ、攪拌下で10質量％含有アルミニウムイソプロポキシドのアルコール溶液（エタノール：イソプロパノール＝8：6の混合液）40ｇを加えて室温で10時間攪拌した。生成物を遠心分離した後、沈殿物をエタノールに再分散した。エタノールに分散したコロイド粒子は白金粒子がアルミナ前駆体で被覆された微粒子であったので、これに少量の水を加えて未反応のイソプロポキシ基を加水分解し、続いてアセトンを過剰量加えて生成物を沈降させ、該沈殿物を空気中７５０℃３時間熱処理することによって、アルミナ（融点約２０５０℃）で被覆された白金微粒子が得られることがわかった。該白金微粒子におけるアルミナ膜の厚みは約５ｎｍであった。したがって、上記で調整したコロイド粒子のエタノール分散液を、適当量だけスポイトで取り、市販の活性アルミナ微粒子（平均粒径2μｍのγアルミナ粉末）に加え、混合、乾燥後、ヘリウム希釈水素（10ｖ/ｖ％）気流下750℃3時間熱処理して、アルミナに分散した触媒を得た。白金の含有率は2質量％であった。
Example 2 Synthesis of Alumina-Coated Platinum Catalyst In a beaker, 50 g of a commercially available platinum colloid dispersion (Tanaka Kikinzoku: average platinum particle size of about 2 nm, platinum content of 4% by mass) and 100 g of ethanol are added and stirred. Below, 40 g of an alcohol solution of aluminum isopropoxide containing 10% by mass (mixed solution of ethanol: isopropanol = 8: 6) was added and stirred at room temperature for 10 hours. After centrifuging the product, the precipitate was redispersed in ethanol. Since the colloidal particles dispersed in ethanol were fine particles in which platinum particles were coated with an alumina precursor, a small amount of water was added thereto to hydrolyze unreacted isopropoxy groups, and then an excess amount of acetone was added. It was found that platinum fine particles coated with alumina (melting point: about 2050 ° C.) can be obtained by settling the product and heat-treating the precipitate in air at 750 ° C. for 3 hours. The thickness of the alumina film in the platinum fine particles was about 5 nm. Therefore, an appropriate amount of the ethanol dispersion of colloidal particles prepared above is taken with a dropper, added to commercially available activated alumina fine particles (γ-alumina powder having an average particle size of 2 μm), mixed, dried, and diluted with helium diluted hydrogen (10v / (v%) Heat treatment was performed at 750 ° C. for 3 hours in an air stream to obtain a catalyst dispersed in alumina. The platinum content was 2% by mass.
「実施例３」ジルコニア被覆白金触媒の合成
ビーカーに、市販の白金コロイド分散液（田中貴金属製：白金の平均粒径約2ｎｍ、白金の含有率4質量％）50ｇ、及びエタノール100ｇを入れ、攪拌下で10質量％含有のジルコニウムテトラプロポキシドのプロパノール溶液20ｇを加えて室温で10時間攪拌した。生成物を遠心分離した後、沈殿物をエタノールに再分散した。エタノールに分散したコロイド粒子は白金粒子がジルコニア前駆体で被覆された微粒子であったので、これに少量の水を加えて未反応のプロポキシ基を加水分解し、続いてアセトンを加えて生成物を沈降させ、該沈殿物を空気中７５０℃で３時間熱処理することによって、ジルコニアで被覆された白金微粒子が得られることがわかった。該白金微粒子におけるジルコニア膜の厚みは約５ｎｍであった。したがって、上記で調整したコロイド粒子のエタノール分散液を、適当量だけスポイトで取り、市販のジルコニア微粒子（平均粒径2μｍのジルコニア粉末）に加え、混合、乾燥後、ヘリウム希釈水素（10ｖ/ｖ％）気流下750℃3時間熱処理して、ジルコニアに分散した触媒を得た。白金の含有率は2質量％であった。
[Example 3] Synthesis of zirconia-coated platinum catalyst In a beaker, 50 g of a commercially available platinum colloidal dispersion (Tanaka Kikinzoku: platinum average particle size of about 2 nm, platinum content of 4% by mass) and 100 g of ethanol were added and stirred. Below, 20 g of a propanol solution of zirconium tetrapropoxide containing 10% by mass was added and stirred at room temperature for 10 hours. After centrifuging the product, the precipitate was redispersed in ethanol. Since the colloidal particles dispersed in ethanol were fine particles in which platinum particles were coated with a zirconia precursor, a small amount of water was added to hydrolyze unreacted propoxy groups, followed by acetone to add the product. It was found that platinum fine particles coated with zirconia were obtained by settling and heat-treating the precipitate in air at 750 ° C. for 3 hours. The thickness of the zirconia film in the platinum fine particles was about 5 nm. Therefore, an appropriate amount of the ethanol dispersion of colloidal particles prepared above is taken with a dropper, added to commercially available zirconia fine particles (zirconia powder with an average particle diameter of 2 μm), mixed, dried, and diluted with helium (10v / v%). ) Heat treatment was performed at 750 ° C. for 3 hours in an air stream to obtain a catalyst dispersed in zirconia. The platinum content was 2% by mass.
「実施例４」チタニア被覆白金触媒の合成
ビーカーに、市販の白金コロイド分散液（田中貴金属製：白金の平均粒径約2ｎｍ、白金の含有率4質量％）50ｇ、及びエタノール100ｇを入れ、攪拌下で10質量％含有のチタニウムテトライソプロポキシドのイソプロパノール溶液20ｇを加えて室温で10時間攪拌した。生成物を遠心分離した後、沈殿物をエタノールに再分散した。エタノールに分散したコロイド粒子は白金粒子がチタニア前駆体で被覆された微粒子であったので、これに少量の水を加えて未反応のイソプロポキシ基を加水分解し、続いてアセトンを加えて生成物を沈降させ、該沈殿物を空気中７５０℃で３時間熱処理することによって、チタニアで被覆された白金微粒子が得られることがわかった。該白金微粒子におけるチタニア膜の厚みは約２ｎｍであった。得られたコロイド粒子のエタノール分散液を、適当量だけスポイトで取り、市販のチタニア微粒子（平均粒径2μｍのチタニア粉末）に加え、混合、乾燥後、ヘリウム希釈水素（10ｖ/ｖ％）気流下750℃3時間熱処理して、チタニアに分散した触媒を得た。白金の含有率は2質量％であった。
[Example 4] Synthesis of titania-coated platinum catalyst In a beaker, 50 g of a commercially available platinum colloidal dispersion (manufactured by Tanaka Kikinzoku: platinum average particle size of about 2 nm, platinum content of 4% by mass) and 100 g of ethanol were added and stirred. Below, 20 g of isopropanol solution of titanium tetraisopropoxide containing 10% by mass was added and stirred at room temperature for 10 hours. After centrifuging the product, the precipitate was redispersed in ethanol. The colloidal particles dispersed in ethanol were platinum particles coated with a titania precursor, so a small amount of water was added to hydrolyze unreacted isopropoxy groups, followed by acetone to produce the product. It was found that platinum fine particles coated with titania were obtained by allowing the precipitate to be heat-treated at 750 ° C. for 3 hours in air. The thickness of the titania film in the platinum fine particles was about 2 nm. Take an appropriate amount of the ethanol dispersion of the colloidal particles with a dropper, add it to commercially available titania fine particles (titania powder with an average particle size of 2 μm), mix, dry, and then in a helium-diluted hydrogen (10v / v%) stream Heat treatment was performed at 750 ° C. for 3 hours to obtain a catalyst dispersed in titania. The platinum content was 2% by mass.
「実施例５」シリカ被覆白金触媒を塗布したモノリス触媒の合成
実施例１のシリカ被覆白金触媒1ｇとコロイダルシリカ0.1ｇを蒸留水10ｍｌに加え、攪拌してスラリーを調整した。これに、市販のコージェライトモノリス成形体（400 cells/in2、直径118ｍｍ×長さ50ｍｍ、重量243ｇ）から切り出したミニ成形体（21 cells、直径8ｍｍ×長さ9ｍｍ、重量0.15ｇ）を5個浸漬し、試料をとりだし風乾後、窒素気流下で750℃-3時間熱処理した。シリカ被覆触媒の付着量はミニ成形体の約10質量％であり、ミニ成形体当たりの白金の担持量は約2質量％であった。
Example 5 Synthesis of Monolith Catalyst Coated with Silica-Coated Platinum Catalyst 1 g of the silica-coated platinum catalyst of Example 1 and 0.1 g of colloidal silica were added to 10 ml of distilled water and stirred to prepare a slurry. Five mini-molded bodies (21 cells, diameter 8 mm x length 9 mm, weight 0.15 g) cut from a commercially available cordierite monolith molded body (400 cells / in2, diameter 118 mm x length 50 mm, weight 243 g) After dipping, the sample was taken out, air-dried, and heat-treated in a nitrogen stream at 750 ° C. for 3 hours. The adhesion amount of the silica-coated catalyst was about 10% by mass of the mini-molded product, and the supported amount of platinum per mini-molded product was about 2% by mass.
「比較例２」還元剤としてエチレンを用いたＮＯｘ処理
比較例１の触媒サンプルを石英製の連続流通式反応管に0.60 g充填し、ヘリウムで濃度調整した一酸化窒素を流通処理した。被処理ガスの成分モル濃度を、一酸化窒素0.1％、酸素14％、水蒸気10％、及びエチレン0.3％とした。反応管へ導入した混合ガスの流量を毎分100 ml、処理温度を100〜300℃とした。50℃ごとに排ガスをサンプリングし、一酸化窒素の浄化処理率を求めた。次ぎに同じ触媒を空気中750℃-24時間熱処理した触媒について上記と同様な条件でＮＯｘ処理を行いフレッシュ触媒の結果と比較した。結果を表１に示した。
Comparative Example 2 NO x Treatment Using Ethylene as Reducing Agent 0.60 g of the catalyst sample of Comparative Example 1 was filled in a quartz continuous flow reaction tube, and nitrogen monoxide whose concentration was adjusted with helium was flow-treated. The component molar concentrations of the gas to be treated were 0.1% nitric oxide, 14% oxygen, 10% water vapor, and 0.3% ethylene. The flow rate of the mixed gas introduced into the reaction tube was 100 ml per minute, and the treatment temperature was 100 to 300 ° C. The exhaust gas was sampled every 50 ° C., and the purification rate of nitric oxide was determined. Next, the same catalyst was heat-treated in air at 750 ° C. for 24 hours and subjected to NO x treatment under the same conditions as described above, and compared with the results of the fresh catalyst. The results are shown in Table 1.
「実施例６〜１０」還元剤としてエチレンを用いたＮＯｘ処理
実施例１〜５の触媒サンプルをそれぞれ石英製の連続流通式反応管に0.6 g充填し、ヘリウムで濃度調整した一酸化窒素を流通処理した。被処理ガスの成分モル濃度を、一酸化窒素0.1％、酸素14％、水蒸気10％、及びエチレン0.3％とした。反応管へ導入した混合ガスの流量を毎分100 ml、処理温度を100〜300℃とした。50℃ごとに排ガスをサンプリングし、一酸化窒素の浄化処理率を求めた。次ぎに同じ触媒サンプルを空気中750℃-24時間熱処理した触媒について上記と同様な条件でＮＯｘ処理を行いフレッシュ触媒の結果と比較した。結果を表１に示した。表1から、比較例の触媒は空気中750℃処理を行うとフレッシュ触媒よりも著しく活性が低下するが、本発明の耐熱性材料で被覆した触媒は、空気中750℃処理後でも、フレッシュ触媒とほとんど同程度の活性を維持することがわかる。特に、シリカ被覆白金触媒は、エチレンなどの炭化水素を還元剤に用いて高濃度酸素共存下でかってない150〜300℃での効率的なＮＯｘ浄化を可能にした。したがって、小型ディーゼル車の排ＮＯｘ処理に適していることがわかる。
“Examples 6 to 10” NO x treatment using ethylene as a reducing agent Each of the catalyst samples of Examples 1 to 5 was filled in a continuous flow reaction tube made of quartz in an amount of 0.6 g, and nitrogen monoxide whose concentration was adjusted with helium was added. Distribution processing. The component molar concentrations of the gas to be treated were 0.1% nitric oxide, 14% oxygen, 10% water vapor, and 0.3% ethylene. The flow rate of the mixed gas introduced into the reaction tube was 100 ml per minute, and the treatment temperature was 100 to 300 ° C. The exhaust gas was sampled every 50 ° C., and the purification rate of nitric oxide was determined. Next, the same catalyst sample was heat-treated in air at 750 ° C. for 24 hours, and subjected to NO x treatment under the same conditions as described above, and compared with the results of the fresh catalyst. The results are shown in Table 1. From Table 1, the activity of the catalyst of the comparative example is significantly lower than that of the fresh catalyst when treated in air at 750 ° C., but the catalyst coated with the heat-resistant material of the present invention is a fresh catalyst even after being treated in air at 750 ° C. It can be seen that the activity of almost the same level is maintained. In particular, the silica-coated platinum catalyst enables efficient NO x purification at 150 to 300 ° C., which is not required in the presence of high-concentration oxygen, using a hydrocarbon such as ethylene as a reducing agent. Therefore, it is understood that suitable waste NO x treatment light duty diesel.
「実施例１１」還元剤としてエチレンを用いリッチバーンを行うＮＯｘ処理
実施例５のモノリス触媒を用いて一酸化窒素を処理した。被処理ガスの成分モル濃度比を、一酸化窒素0.1％、酸素1％、エチレン1％とした。該調整ガスの流量を毎分100 ml、処理温度を100〜600℃とした。処理後の排ガスに含まれるＮＯｘを定量分析し一酸化窒素の浄化処理率を求めた。結果を表2に示した。表2から、本発明触媒をモノリス成形体に塗布して成る触媒は、炭化水素を還元剤に用いてリッチバーンの条件にあるＮＯｘを中温領域から高温領域にわたって効率よく浄化できることがわかる。したがって、例えば、リーンバーンとリッチバーンを交互に行えば、実施例7の触媒は、広い温度範囲でＮＯｘを除去できるので、リーンバーンとリッチバーンを交互に行うことのできる小型ディーゼル車の排ＮＯｘ処理に適していることがわかる。
[Example 11] NO x treatment in which rich burn is performed using ethylene as a reducing agent Nitric oxide was treated using the monolith catalyst of Example 5. The component molar concentration ratio of the gas to be treated was 0.1% nitric oxide, 1% oxygen, and 1% ethylene. The flow rate of the adjustment gas was 100 ml per minute, and the treatment temperature was 100 to 600 ° C. The NO x contained in the exhaust gas after the treatment was determined purification treatment ratio of nitrogen monoxide was quantitatively analyzed. The results are shown in Table 2. From Table 2, the catalyst of the present invention catalyst formed by coating a monolithic molded body, it can be seen that the NO x in the condition of the rich burn using hydrocarbon as a reducing agent can efficiently purify over high-temperature region from the intermediate temperature region. Thus, for example, by performing lean burn and rich-burn alternately, the catalyst of Example 7, it is possible to remove the NO x over a wide temperature range, and discharge of small diesel vehicles capable of performing lean-burn and rich-burn alternately it is seen to be suitable for NO x treatment.
「実施例１２」還元剤としてアンモニアを用いたＮＯｘ処理
実施例５のモノリス触媒を用いて一酸化窒素を処理した。被処理ガスの成分モル濃度比を、一酸化窒素0.1％、酸素14％、水蒸気10%、アンモニア0.3％とした。該調整ガスの流量を毎分100 ml、処理温度を100〜600℃とした。処理後の排ガスに含まれるＮＯｘを定量分析し一酸化窒素の浄化処理率を求めた。結果を表3に示した。表3から、本発明触媒をモノリス成形体に塗布して成る触媒は、アンモニアを還元剤として用いても高濃度酸素共存下でのＮＯｘを効率よく浄化できることがわかる。したがって、アンモニア源としての尿素供給システムを搭載している大型ディーゼル車の排ＮＯｘ浄化処理に適していることがわかる。
Was treated with nitric oxide using a monolithic catalyst of the NO x process Example 5 using ammonia as "Example 12" reducing agent. The component molar concentration ratio of the gas to be treated was 0.1% nitric oxide, 14% oxygen, 10% water vapor, and 0.3% ammonia. The flow rate of the adjustment gas was 100 ml per minute, and the treatment temperature was 100 to 600 ° C. The NO x contained in the exhaust gas after the treatment was determined purification treatment ratio of nitrogen monoxide was quantitatively analyzed. The results are shown in Table 3. From Table 3, the present invention catalyst catalyst formed by coating a monolithic molded body, ammonia it can be seen that also efficiently purify NO x under high concentrations of oxygen coexist used as the reducing agent. Therefore, it is understood that suitable for discharging the NO x purification process of a large diesel vehicles are equipped with urea supply system as ammonia source.
以上実施例比較例の結果、本発明の排ＮＯｘ浄化用触媒は、従来困難であったディーゼル排ＮＯｘ処理を長期間効率的に行うために、リーンバーンの比較的高濃度酸素雰囲気下での高温の排ＮＯｘに対しても高活性を維持してシンタリング焼結の欠点を同時に満足する新規の耐熱性触媒を提供することが出来る。例えば、三元触媒では酸素濃度14％の雰囲気下における一酸化窒素はほとんど浄化できないが、本発明のシリカで被覆した白金触媒は、酸素濃度14％の雰囲気に共存する一酸化窒素の80％以上を150〜300℃において浄化することができ、空気中750℃での熱処理後でも熱処理前の触媒の触媒活性と同程度の高活性を示した。 As a result of the comparative examples described above, the exhaust NO x purification catalyst of the present invention is used in a relatively high-concentration oxygen atmosphere of lean burn in order to efficiently perform long-term diesel exhaust NO x treatment, which has been difficult in the past. it is possible to provide a novel heat-resistant catalyst simultaneously satisfies the shortcomings of sintering sintering be maintained high activity to a high-temperature exhaust NO x. For example, a three-way catalyst can hardly purify nitrogen monoxide in an atmosphere with an oxygen concentration of 14%, but the platinum catalyst coated with silica of the present invention is 80% or more of nitrogen monoxide coexisting in an atmosphere with an oxygen concentration of 14%. Was able to be purified at 150 to 300 ° C., and even after heat treatment at 750 ° C. in air, high activity comparable to that of the catalyst before heat treatment was exhibited.
本発明の耐熱性材料で被覆した白金含有触媒は、ディーゼル排ＮＯｘ浄化用触媒として有用である。 Platinum-containing catalyst coated with heat-resistant material of the present invention is useful as a diesel exhaust the NO x purification catalyst.
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| JP4285095B2 (en) * | 2003-06-12 | 2009-06-24 | トヨタ自動車株式会社 | Exhaust gas purification catalyst and exhaust gas purification method |
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2005
- 2005-04-25 JP JP2005127099A patent/JP4753613B2/en not_active Expired - Fee Related
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| JP2006297349A (en) | 2006-11-02 |
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