JP2009247955A - Method of manufacturing catalyst - Google Patents

Method of manufacturing catalyst Download PDF

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JP2009247955A
JP2009247955A JP2008097080A JP2008097080A JP2009247955A JP 2009247955 A JP2009247955 A JP 2009247955A JP 2008097080 A JP2008097080 A JP 2008097080A JP 2008097080 A JP2008097080 A JP 2008097080A JP 2009247955 A JP2009247955 A JP 2009247955A
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catalyst
noble metal
exhaust gas
metal particles
oxygen
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JP5031642B2 (en
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Kazuyuki Taji
和幸 田路
Hideshi Takahashi
英志 高橋
Koichi Yuzaki
浩一 湯崎
Tatsuro Miyazaki
達郎 宮崎
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Tohoku University NUC
Dowa Electronics Materials Co Ltd
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Dowa Electronics Materials Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a catalyst, which can manufacture a catalyst usable as an exhaust purification catalyst which forms noble metal nanocluster on the surface of a carrier made of a composite oxide including Ce and Bi and oxygen for improving purification performance for harmful gases such as carbon hydride (HC) and carbon monoxide (CO) in the exhaust gas of a diesel engine. <P>SOLUTION: After noble metal particles of Pt or the like are dispersed and supported in the carrier made of a composite oxide containing Ce and Bi and oxygen as components, the noble metal particles are protected by an organic molecule, and thereafter, the organic molecule is baked and carbonated by heat treatment in an inert gas atmosphere. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、触媒の製造方法に関し、特に、ディーゼルエンジンの排ガス中の一酸化炭素および炭化水素の浄化に適した排ガス浄化触媒として使用可能な触媒の製造方法に関する。   The present invention relates to a method for producing a catalyst, and more particularly to a method for producing a catalyst that can be used as an exhaust gas purification catalyst suitable for purification of carbon monoxide and hydrocarbons in exhaust gas from a diesel engine.

従来、ディーゼルエンジンの排ガス中の一酸化炭素(CO)や炭化水素(HC)などの有害ガスを低温で効率的に酸化することができる排ガス浄化触媒として、アルミナからなる担体に貴金属が担持された排ガス浄化触媒や、チタニアとゼオライトを含有する担体に貴金属が担持された排ガス浄化触媒(例えば、特許文献1参照)などが提案されている。   Conventionally, a noble metal is supported on a support made of alumina as an exhaust gas purification catalyst capable of efficiently oxidizing harmful gases such as carbon monoxide (CO) and hydrocarbons (HC) in exhaust gas of a diesel engine at a low temperature. An exhaust gas purification catalyst, an exhaust gas purification catalyst in which a noble metal is supported on a carrier containing titania and zeolite (see, for example, Patent Document 1) have been proposed.

一方、ディーゼルエンジンの排ガスには、カーボンを主体とする粒子状物質(以下「PM」という)が含まれており、ディーゼルエンジンの排ガスからPMを除去する方法として、一般に、排気ガス流路に多孔質体セラミックスからなるディーゼル・パーティキュレート・フィルタ(以下、「DPF」という)を設置してPMを捕集(トラップ)する方法が用いられている。DPFに捕集されたPMは間欠的または連続的に燃焼処理され、DPFはPMの捕集前の状態に再生される。このDPFの再生処理には、一般に、電気ヒーターやバーナーなどによって外部から強制加熱してPMを燃焼させる方法や、DPFよりもエンジン側に酸化触媒を設置し、排ガス中に含まれるNOを酸化触媒によってNOにして、NOの酸化力によってPMを燃焼させる方法などが用いられている。 On the other hand, the exhaust gas of a diesel engine contains particulate matter (hereinafter referred to as “PM”) mainly composed of carbon. As a method for removing PM from the exhaust gas of a diesel engine, the exhaust gas passage is generally porous. A method of collecting PM (trap) by installing a diesel particulate filter (hereinafter referred to as “DPF”) made of a material ceramic is used. The PM collected in the DPF is burned intermittently or continuously, and the DPF is regenerated to the state before the PM is collected. This DPF regeneration process is generally performed by a method of burning PM by forcibly heating from the outside with an electric heater, a burner, or the like, or by installing an oxidation catalyst on the engine side of the DPF, and converting NO contained in the exhaust gas into an oxidation catalyst. in the NO 2 by a method for combusting PM by the oxidation force of the NO 2 is used.

このようなディーゼルエンジンの排ガスからPMを低温で燃焼させることができる排ガス浄化触媒として、白金(Pt)などの貴金属元素を含まず、セリウム(Ce)とビスマス(Bi)と酸素から構成される複合酸化物を使用することが提案されている(例えば、特許文献2参照)。   As an exhaust gas purifying catalyst capable of burning PM from exhaust gas of such a diesel engine at a low temperature, it is a composite composed of cerium (Ce), bismuth (Bi) and oxygen without containing noble metal elements such as platinum (Pt). It has been proposed to use an oxide (for example, see Patent Document 2).

特開2006−81988号公報(段落番号0013−0014)JP 2006-81988 A (paragraph number 0013-0014) 特開2007−216150号公報(段落番号0008−0009)Japanese Patent Laying-Open No. 2007-216150 (paragraph numbers 0008-0009)

しかし、アルミナからなる担体に貴金属が担持された排ガス浄化触媒では、担体として使用するアルミナが、ディーゼルエンジンの排ガス中の硫黄化合物により被毒して劣化し易いという問題がある。また、特許文献1で提案されたチタニアとゼオライトを含有する担体に貴金属が担持された排ガス浄化触媒では、特許文献2で提案されたCeとBiと酸素から構成される複合酸化物を使用する排ガス浄化触媒と比べて、ディーゼルエンジンの排ガスからのPMの除去性能が格段に低くなる。   However, in an exhaust gas purification catalyst in which a noble metal is supported on a support made of alumina, there is a problem that alumina used as the support is easily poisoned and deteriorated by sulfur compounds in the exhaust gas of a diesel engine. Further, in the exhaust gas purifying catalyst proposed in Patent Document 1 in which a noble metal is supported on a support containing titania and zeolite, the exhaust gas using a composite oxide composed of Ce, Bi and oxygen proposed in Patent Document 2 is used. Compared with the purification catalyst, the PM removal performance from the exhaust gas of the diesel engine is remarkably lowered.

一方、特許文献2で提案されたCeとBiと酸素から構成される複合酸化物を使用する排ガス浄化触媒は、ディーゼルエンジンの排ガスからPMを低温で燃焼させることができるが、ディーゼルエンジンの排ガス中の一酸化炭素(CO)や炭化水素(HC)などの有害ガスも低温で効率的に酸化することができるようにするのが望ましい。   On the other hand, the exhaust gas purification catalyst using a composite oxide composed of Ce, Bi and oxygen proposed in Patent Document 2 can burn PM from exhaust gas of a diesel engine at a low temperature. It is desirable that harmful gases such as carbon monoxide (CO) and hydrocarbons (HC) can be efficiently oxidized at low temperatures.

そこで、本発明者らは、CeとBiと酸素から構成される複合酸化物を使用する排ガス浄化触媒のディーゼルエンジンの排ガス中の一酸化炭素(CO)や炭化水素(HC)などの浄化性能を向上させるために、CeとBiと酸素から構成される複合酸化物からなる担体に、蒸発乾固法(担体に活性成分を含む過剰の溶液に加えて溶媒を加熱蒸発させる方法)やincipient wetness法(ポアフィリング法)(活性成分を含む溶液をごく僅かずつ加えて担体表面が均一に濡れ始めた状態で含浸を終了する方法)などの従来の方法により、CeとBiと酸素から構成される複合酸化物からなる担体にPt、Pd、Rhなどの貴金属が担持された触媒を製造することを試みたが、ディーゼルエンジンの排ガス中の一酸化炭素(CO)や炭化水素(HC)などの浄化性能を向上させることができなかった。   Therefore, the present inventors have a purification performance of carbon monoxide (CO), hydrocarbon (HC), etc. in the exhaust gas of a diesel engine of an exhaust gas purification catalyst using a composite oxide composed of Ce, Bi and oxygen. In order to improve, a carrier comprising a complex oxide composed of Ce, Bi and oxygen is evaporated to dryness (a method in which a solvent is heated and evaporated in addition to an excess solution containing an active ingredient in the carrier) or an incipient wetness method. (Pore-filling method) (composition composed of Ce, Bi and oxygen by a conventional method such as adding a solution containing an active ingredient little by little and ending the impregnation in a state where the surface of the carrier begins to get wet uniformly) An attempt was made to produce a catalyst in which a noble metal such as Pt, Pd, Rh, etc. was supported on an oxide carrier. Carbon monoxide (CO) in the exhaust gas of a diesel engine Could not be improved purification performance, such as hydrocarbons (HC).

また、触媒の活性は、原子状の触媒金属が高分散で担持された触媒よりも、触媒金属原子がナノクラスター状態で担持されている触媒の方が高いことが知られているが、上記の従来の方法によりCeとBiと酸素から構成される複合酸化物からなる担体に貴金属が担持された触媒を透過型電子顕微鏡(TEM)で観察したところ、担体の表面に貴金属のクラスターは存在しなかった。この触媒では、貴金属が原子状で担持されているか、あるいは、担体の内部に取り込まれたことにより、貴金属が担持された効果が極めて低くなっていると考えられる。   Further, it is known that the catalyst activity is higher in the catalyst in which the catalyst metal atoms are supported in the nanocluster state than the catalyst in which the atomic catalyst metal is supported in a highly dispersed state. When a catalyst in which a noble metal is supported on a support made of a complex oxide composed of Ce, Bi, and oxygen by a conventional method is observed with a transmission electron microscope (TEM), no noble metal cluster exists on the surface of the support. It was. In this catalyst, it is considered that the effect of supporting the noble metal is extremely low because the noble metal is supported in an atomic form or taken into the support.

したがって、本発明は、このような従来の問題点に鑑み、CeとBiと酸素から構成される複合酸化物からなる担体の表面に貴金属ナノクラスターを形成して、ディーゼルエンジンの排ガス中の一酸化炭素(CO)や炭化水素(HC)などの有害ガスの浄化性能を向上させる排ガス浄化触媒として使用可能な触媒を製造することができる、触媒の製造方法を提供することを目的とする。   Therefore, in view of such a conventional problem, the present invention forms a noble metal nanocluster on the surface of a support composed of a composite oxide composed of Ce, Bi and oxygen, and thereby monoxide in the exhaust gas of a diesel engine. An object of the present invention is to provide a catalyst production method capable of producing a catalyst that can be used as an exhaust gas purification catalyst that improves the purification performance of harmful gases such as carbon (CO) and hydrocarbons (HC).

本発明者らは、上記課題を解決するために鋭意研究した結果、CeとBiと酸素を構成元素として含む複合酸化物からなる担体に貴金属粒子を分散して担持させた後、貴金属粒子を有機分子で保護し、その後、不活性ガス雰囲気中で熱処理することにより、CeとBiと酸素から構成される複合酸化物からなる担体の表面に貴金属ナノクラスターを形成して、ディーゼルエンジンの排ガス中の一酸化炭素(CO)や炭化水素(HC)などの有害ガスの浄化性能を向上させる排ガス浄化触媒として使用可能な触媒を製造することができることを見出し、本発明を完成するに至った。   As a result of intensive studies to solve the above problems, the present inventors have dispersed noble metal particles on a support made of a composite oxide containing Ce, Bi, and oxygen as constituent elements, and then supported the noble metal particles in an organic form. By protecting with molecules and then heat-treating in an inert gas atmosphere, noble metal nanoclusters are formed on the surface of the support composed of a composite oxide composed of Ce, Bi and oxygen, and in the exhaust gas of diesel engines It has been found that a catalyst that can be used as an exhaust gas purification catalyst that improves the purification performance of harmful gases such as carbon monoxide (CO) and hydrocarbons (HC) can be produced, and the present invention has been completed.

すなわち、本発明による触媒の製造方法は、CeとBiと酸素を構成元素として含む複合酸化物からなる担体に貴金属粒子を分散して担持させた後、貴金属粒子を有機分子で保護し、その後、不活性ガス雰囲気中で熱処理することを特徴とする。この触媒の製造方法において、不活性ガス雰囲気中で熱処理した後、水素雰囲気中および空気または酸素雰囲気中の少なくとも一方の雰囲気中で熱処理してもよい。また、不活性ガス雰囲気中で熱処理する温度が、有機分子を焼成して炭化させる温度であるのが好ましい。さらに、有機分子が、ポリビニルピロリドン、ポリビニルアルコール、ポリエチレンイミド、ポリアクリル酸、シュウ酸、クエン酸、マレイン酸およびこれらの混合物からなる群から選ばれるのが好ましく、貴金属粒子が、Pt、PdおよびRhからなる群から選ばれる貴金属の粒子であるのが好ましい。   That is, in the method for producing a catalyst according to the present invention, after precious metal particles are dispersed and supported on a support made of a composite oxide containing Ce, Bi and oxygen as constituent elements, the precious metal particles are protected with organic molecules, and then Heat treatment is performed in an inert gas atmosphere. In this catalyst manufacturing method, after heat treatment in an inert gas atmosphere, heat treatment may be performed in a hydrogen atmosphere and / or an atmosphere of air or oxygen. Moreover, it is preferable that the temperature which heat-processes in inert gas atmosphere is a temperature which bakes and carbonizes an organic molecule. Furthermore, the organic molecule is preferably selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, polyethyleneimide, polyacrylic acid, oxalic acid, citric acid, maleic acid and mixtures thereof, and the noble metal particles are Pt, Pd and Rh. The particles are preferably noble metal particles selected from the group consisting of:

本発明によれば、CeとBiと酸素から構成される複合酸化物からなる担体の表面に貴金属ナノクラスターを形成して、ディーゼルエンジンの排ガス中の一酸化炭素(CO)や炭化水素(HC)などの有害ガスの浄化性能を向上させる排ガス浄化触媒として使用可能な触媒を製造することができる。   According to the present invention, noble metal nanoclusters are formed on the surface of a support composed of a complex oxide composed of Ce, Bi and oxygen, and carbon monoxide (CO) and hydrocarbon (HC) in exhaust gas from a diesel engine. Thus, it is possible to produce a catalyst that can be used as an exhaust gas purification catalyst that improves the purification performance of harmful gases.

以下、図1を参照して、本発明による触媒の製造方法の実施の形態について説明する。   Hereinafter, an embodiment of a method for producing a catalyst according to the present invention will be described with reference to FIG.

まず、CeとBiと酸素から構成される複合酸化物からなる担体1が分散した分散液中において担体1の表面電位を利用して、担体1に貴金属錯イオンを静電的に吸着させ、その後、還元剤で化学的に還元すると、図1(a)に示すように、担体1に貴金属粒子2が分散して担持された状態になる。次に、貴金属に配位し易い有機分子を投入して攪拌すると、図1(b)に示すように、貴金属粒子2に有機分子3が選択的に配位した状態になる。このようにして得られた触媒前駆体の分散液を濾過し、洗浄し、乾燥した後、不活性ガス雰囲気中で焼成すると、図1(c)に示すように、有機分子3が炭化してそのまま残留するため、熱処理中の貴金属粒子2の移動が抑制され、貴金属粒子2が担体1の表面にナノサイズで固定される。その後、水素雰囲気中および空気または酸素雰囲気中の少なくとも一方の雰囲気中で熱処理することによって、図1(d)に示すように、炭化物4を除去した状態にしてもよい。なお、空気または酸素雰囲気中で熱処理する場合は、300〜400℃程度で燃焼させて除去するのが好ましい。   First, a noble metal complex ion is electrostatically adsorbed on the carrier 1 using the surface potential of the carrier 1 in a dispersion in which the carrier 1 made of a complex oxide composed of Ce, Bi and oxygen is dispersed. When chemically reduced with a reducing agent, the noble metal particles 2 are dispersed and supported on the carrier 1 as shown in FIG. Next, when an organic molecule that easily coordinates to the noble metal is added and stirred, the organic molecule 3 is selectively coordinated to the noble metal particle 2 as shown in FIG. The catalyst precursor dispersion thus obtained is filtered, washed, dried, and then fired in an inert gas atmosphere. As shown in FIG. 1 (c), the organic molecules 3 are carbonized. Since it remains as it is, the movement of the noble metal particles 2 during the heat treatment is suppressed, and the noble metal particles 2 are fixed to the surface of the carrier 1 in a nano size. Thereafter, the carbide 4 may be removed by heat treatment in at least one of a hydrogen atmosphere and an air or oxygen atmosphere as shown in FIG. In addition, when heat-treating in an air or oxygen atmosphere, it is preferable to remove it by burning at about 300 to 400 ° C.

このように、本発明による触媒の製造方法の実施の形態では、貴金属に選択的に配位する性質をもつ有機分子を添加することによって、CeとBiと酸素から構成される複合酸化物からなる担体に担持されている貴金属粒子を保護し、その後の熱処理工程における貴金属の熱移動を抑制して、担体の表面に貴金属ナノクラスターを形成することができる。   As described above, in the embodiment of the method for producing a catalyst according to the present invention, an organic molecule having a property of selectively coordinating to a noble metal is added to form a composite oxide composed of Ce, Bi, and oxygen. It is possible to protect the noble metal particles supported on the carrier, suppress the heat transfer of the noble metal in the subsequent heat treatment step, and form noble metal nanoclusters on the surface of the carrier.

一般に、触媒は、反応条件によって決定される反応系の化学平衡に達するまでの反応速度を変化させるので、反応速度を向上させるために反応系の温度や圧力を上昇させる。そのため、ナノサイズの粒子が担体の表面に担持された触媒では、反応系の温度や圧力が上昇した環境下においてナノサイズの粒子の焼結(シンタリング)が進行し、反応に寄与する触媒の表面積や活性点が減少して、触媒の活性が次第に低下する。しかし、本発明による触媒の製造方法の実施の形態では、担体の表面に分散して担持されたナノサイズの貴金属粒子をポリビニルピロリドン(PVP)などの有機分子で保護し、その後、高温で熱処理して有機分子を焼成して炭化することによって、触媒の活性点を表面に露出させるとともに、生成した炭素による粒子の焼結を防止して、ナノサイズの粒子が担体の表面に担持された触媒の劣化を防止することができる。したがって、本発明による触媒の製造方法の実施の形態によって製造された触媒は、ディーゼルエンジンの排ガス中の一酸化炭素および炭化水素の浄化に適した排ガス浄化触媒として使用することができるだけでなく、化学工学や石油化学などの高温や高圧における触媒反応に使用する触媒としても使用することができる。   In general, the catalyst changes the reaction rate until the chemical equilibrium of the reaction system determined by the reaction conditions is reached, so that the temperature and pressure of the reaction system are increased in order to improve the reaction rate. For this reason, in a catalyst in which nano-sized particles are supported on the surface of the support, sintering (sintering) of the nano-sized particles proceeds in an environment in which the temperature and pressure of the reaction system are increased, and the catalyst contributing to the reaction. The surface area and active sites decrease, and the activity of the catalyst gradually decreases. However, in the embodiment of the method for producing a catalyst according to the present invention, nano-sized noble metal particles dispersed and supported on the surface of the support are protected with organic molecules such as polyvinyl pyrrolidone (PVP), and then heat-treated at a high temperature. By calcination and carbonization of organic molecules, the active sites of the catalyst are exposed to the surface, and sintering of the particles by the generated carbon is prevented, so that the nano-sized particles are supported on the surface of the support. Deterioration can be prevented. Therefore, the catalyst produced by the embodiment of the method for producing a catalyst according to the present invention can be used not only as an exhaust gas purification catalyst suitable for purification of carbon monoxide and hydrocarbons in exhaust gas of a diesel engine, but also as a chemical. It can also be used as a catalyst used in catalytic reactions at high temperatures and high pressures such as engineering and petrochemistry.

以下、本発明による触媒の製造方法の実施例について詳細に説明する。   Examples of the method for producing a catalyst according to the present invention will be described in detail below.

[実施例1]
まず、CeとBiと酸素から構成される複合酸化物としてCe0.9Bi0.17gを蒸留水30mLに入れて超音波で1時間分散させた後、一晩攪拌して溶液中にCe0.9Bi0.1を十分に分散させた。また、この攪拌中の溶液にPt前駆溶液(KPtCl)と錯化剤(NaCl)を投入した後、pHを3に調整して、表面がプラスにチャージされたCe0.9Bi0.1にPt錯イオン([Pt2+(Cl])を静電的に吸着させた。
[Example 1]
First, 7 g of Ce 0.9 Bi 0.1 O 2 as a composite oxide composed of Ce, Bi, and oxygen was placed in 30 mL of distilled water and dispersed with ultrasound for 1 hour, and then stirred overnight in the solution. Ce 0.9 Bi 0.1 O 2 was sufficiently dispersed in the mixture. In addition, after adding a Pt precursor solution (K 2 PtCl 4 ) and a complexing agent (NaCl) to this stirring solution, the pH was adjusted to 3 and the surface was positively charged with Ce 0.9 Bi 0. .1 Pt complex ions ([Pt 2+ (Cl ) 4 ]) were electrostatically adsorbed on O 2 .

次に、pHを3に調整したヒドラジン溶液2mLを添加し、さらに1時間攪拌して、Pt錯イオンを還元した後、PVP500mgを添加して、さらに30分間攪拌し、得られた溶液を濾過し、洗浄し、乾燥して粉末を得た。   Next, 2 mL of a hydrazine solution adjusted to pH 3 was added, and the mixture was further stirred for 1 hour to reduce Pt complex ions, and then 500 mg of PVP was added, and the mixture was further stirred for 30 minutes, and the resulting solution was filtered. , Washed and dried to obtain a powder.

この粉末を窒素気流中において400℃で1時間熱処理した後、窒素気流中において800℃で1時間熱処理して、1質量%のPtを含むCe0.9Bi0.1粉末を得た。 This powder was heat-treated at 400 ° C. for 1 hour in a nitrogen stream, and then heat-treated at 800 ° C. for 1 hour in a nitrogen stream to obtain Ce 0.9 Bi 0.1 O 2 powder containing 1% by mass of Pt. .

このようにして得られた1質量%のPtを含むCe0.9Bi0.1粉末(触媒粉末)の貴金属粒子の粒径を測定した。この貴金属粒子の粒径を測定するために、次のようにTEM−EDX(透過型電子顕微鏡−エネルギー分散型X線検出器)による測定を行った。まず、触媒粉末をメタノールに入れて超音波で十分に分散させた後、TEMグリッドに滴下して測定試料を用意した。この測定試料について、透過型電子顕微鏡(TEM)(日立製作所製のHF−2000)により加速電圧200kVで観察し、結晶粒の分散状態を調べた。この観察で得られた映像中においてコントラストの部分に焦点をあてて金属種を限定し、その金属の粒径を測定した。このTEM−EDX測定により、図2のTEM写真に示すように、Ce0.9Bi0.1の表面に粒径2〜5nmのPtクラスターが(丸印で囲んだ位置に)明瞭に分散しているのが観察された。このように800℃の熱処理を行っても、Ce0.9Bi0.1の表面にPtクラスターが熱処理前と同等の粒径2〜5nmを維持したまま分散して担持されていることから、本実施例のように、有機分子としてPVPを添加することによって、熱処理の有無にかかわらず、Ce0.9Bi0.1の表面に粒径2〜5nmのPtクラスターを安定して形成することができることがわかった。 The particle diameter of the noble metal particles of Ce 0.9 Bi 0.1 O 2 powder (catalyst powder) containing 1% by mass of Pt thus obtained was measured. In order to measure the particle size of the noble metal particles, measurement was performed with a TEM-EDX (transmission electron microscope-energy dispersive X-ray detector) as follows. First, the catalyst powder was put in methanol and sufficiently dispersed with ultrasonic waves, and then dropped onto a TEM grid to prepare a measurement sample. This measurement sample was observed with a transmission electron microscope (TEM) (HF-2000 manufactured by Hitachi, Ltd.) at an acceleration voltage of 200 kV to examine the dispersion state of the crystal grains. In the image obtained by this observation, the metal type was limited by focusing on the contrast portion, and the particle size of the metal was measured. By this TEM-EDX measurement, as shown in the TEM photograph of FIG. 2, a Pt cluster having a particle diameter of 2 to 5 nm is clearly formed on the surface of Ce 0.9 Bi 0.1 O 2 (at a position surrounded by a circle). Dispersion was observed. Thus, even when heat treatment at 800 ° C. is performed, the Pt clusters are dispersed and supported on the surface of Ce 0.9 Bi 0.1 O 2 while maintaining the same particle diameter of 2 to 5 nm as before the heat treatment. Thus, as in this example, by adding PVP as an organic molecule, a Pt cluster having a particle size of 2 to 5 nm is stabilized on the surface of Ce 0.9 Bi 0.1 O 2 regardless of the presence or absence of heat treatment. It was found that can be formed.

次に、本実施例で得られた触媒粉末の排ガス浄化触媒としての性能を評価した。まず、固定床流通系反応器に1〜2mmの触媒ペレット1.84gを充填し、表1に示す組成のディーゼル排ガスの模擬混合ガスを室温において全ガス流量8L/分で流通させた。次に、出口側のCO濃度を赤外分析計(堀場製作所製のVIA−510)、C濃度を水素イオン化法分析計(堀場製作所製のFIA−510)によってそれぞれモニタリングしながら、触媒充填層の温度を室温から500℃まで昇温し、CO転化率(%)=(入口CO濃度−出口CO濃度)×100/入口CO濃度、C転化率(%)=(入口C濃度−出口C濃度)×100/入口C濃度から、CO転化率(%)およびC転化率(%)を求めた。その結果、表2に示すように、CO転化率は、200℃で84.9%、250℃で93.1%であり、C転化率は、200℃で54.9%、250℃で77.2%であった。なお、担体としてのCe0.9Bi0.1のCO転化率は、200℃で78.1%、250℃で84.1%であり、C転化率は、200℃で46.6%、250℃で56.3%であった。 Next, the performance of the catalyst powder obtained in this example as an exhaust gas purification catalyst was evaluated. First, 1.84 g of 1 to 2 mm catalyst pellets were charged into a fixed bed flow system reactor, and a simulated mixed gas of diesel exhaust gas having the composition shown in Table 1 was passed at room temperature at a total gas flow rate of 8 L / min. Next, while monitoring the CO concentration on the outlet side by an infrared analyzer (VIA-510 manufactured by Horiba, Ltd.) and the C 3 H 6 concentration by a hydrogen ionization analyzer (FIA-510 manufactured by Horiba, Ltd.), the catalyst The temperature of the packed bed is raised from room temperature to 500 ° C., CO conversion (%) = (inlet CO concentration−outlet CO concentration) × 100 / inlet CO concentration, C 3 H 6 conversion (%) = (inlet C The CO conversion rate (%) and the C 3 H 6 conversion rate (%) were determined from 3 H 6 concentration−outlet C 3 H 6 concentration) × 100 / inlet C 3 H 6 concentration. As a result, as shown in Table 2, the CO conversion rate was 84.9% at 200 ° C. and 93.1% at 250 ° C., and the C 3 H 6 conversion rate was 54.9%, 250 at 200 ° C. It was 77.2% at ° C. The CO conversion rate of Ce 0.9 Bi 0.1 O 2 as a carrier is 78.1% at 200 ° C. and 84.1% at 250 ° C., and the C 3 H 6 conversion rate is 200 ° C. It was 46.6% and 56.3% at 250 ° C.

Figure 2009247955
Figure 2009247955

Figure 2009247955
Figure 2009247955

[実施例2]
窒素気流中において800℃で1時間熱処理した後に、水素気流中において400℃で2時間還元処理した以外は、実施例1と同様の方法により、Ptを含むCe0.9Bi0.1粉末を得た。
[Example 2]
Ce 0.9 Bi 0.1 O 2 containing Pt was produced in the same manner as in Example 1 except that heat treatment was performed at 800 ° C. for 1 hour in a nitrogen stream and then reduction treatment was performed at 400 ° C. for 2 hours in a hydrogen stream. A powder was obtained.

このようにして得られた触媒粉末について、実施例1と同様の方法により、排ガス浄化触媒としての性能を評価した。その結果、表2に示すように、CO転化率は、200℃で85.3%、250℃で92.5%であり、C転化率は、200℃で55.9%、250℃で73.8%であった。 With respect to the catalyst powder thus obtained, the performance as an exhaust gas purification catalyst was evaluated by the same method as in Example 1. As a result, as shown in Table 2, the CO conversion was 85.3% at 200 ° C. and 92.5% at 250 ° C., and the C 3 H 6 conversion was 55.9% at 250 ° C. It was 73.8% at ° C.

[比較例1]
有機分子としてのPVPを添加せず、窒素気流中において400℃で1時間熱処理した後に窒素気流中において800℃で1時間熱処理する代わりに、空気中において800℃で2時間焼成(昇温速度5℃/分)した以外は、実施例1と同様の方法により、1質量%のPtを含むCe0.9Bi0.1粉末を得た。
[Comparative Example 1]
Instead of adding PVP as an organic molecule and heat-treating at 400 ° C. for 1 hour in a nitrogen stream and then heat-treating at 800 ° C. for 1 hour in a nitrogen stream, firing in air at 800 ° C. for 2 hours (heating rate 5) (C / min), a Ce 0.9 Bi 0.1 O 2 powder containing 1% by mass of Pt was obtained in the same manner as in Example 1.

このようにして得られた触媒粉末について、実施例1と同様の方法により、排ガス浄化触媒としての性能を評価した。その結果、表2に示すように、CO転化率は、200℃で72.0%、250℃で76.2%であり、C転化率は、200℃で41.4%、250℃で49.8%であった。 With respect to the catalyst powder thus obtained, the performance as an exhaust gas purification catalyst was evaluated by the same method as in Example 1. As a result, as shown in Table 2, the CO conversion was 72.0% at 200 ° C. and 76.2% at 250 ° C., and the C 3 H 6 conversion was 41.4% at 250 ° C. It was 49.8% at ° C.

[比較例2]
まず、Pt濃度8.486質量%のPt(NH(NO溶液3.571gに純水180mLを加えて金属塩溶液を製造した。この溶液をマグネティックスターラーで攪拌しながら、溶液中にCe0.9Bi0.130gを投入した後、さらに1時間攪拌した。
[Comparative Example 2]
First, 180 mL of pure water was added to 3.571 g of a Pt (NH 3 ) 2 (NO 2 ) 2 solution having a Pt concentration of 8.486% by mass to produce a metal salt solution. While stirring this solution with a magnetic stirrer, 30 g of Ce 0.9 Bi 0.1 O 2 was added to the solution, and the mixture was further stirred for 1 hour.

得られた溶液をエバポレーターに移し、温度80℃、回転速度25rpmで溶媒を除去して粉末を得た。この粉末を130℃で一晩乾燥させた後、空気中において500℃で2時間焼成(昇温速度5℃/分)して、1質量%のPtを含むCe0.9Bi0.1粉末を得た。 The obtained solution was transferred to an evaporator, and the solvent was removed at a temperature of 80 ° C. and a rotation speed of 25 rpm to obtain a powder. This powder was dried at 130 ° C. overnight and then calcined in air at 500 ° C. for 2 hours (heating rate: 5 ° C./min) to obtain Ce 0.9 Bi 0.1 O containing 1% by mass of Pt. Two powders were obtained.

このようにして得られた触媒粉末について、実施例1と同様の方法により、TEM−EDX測定を行った。その結果、Ce0.9Bi0.1の表面にPtのクラスターは観察されず、PtマッピングからPtが担体酸化物中に均質に(原子状に近い状態で)存在していた。 The catalyst powder thus obtained was subjected to TEM-EDX measurement by the same method as in Example 1. As a result, no Pt cluster was observed on the surface of Ce 0.9 Bi 0.1 O 2 , and Pt was present homogeneously (in an atomic state) in the support oxide from the Pt mapping.

また、本比較例で得られた触媒粉末について、実施例1と同様の方法により、排ガス浄化触媒としての性能を評価した。その結果、表2に示すように、CO転化率は、200℃で63.1%、250℃で78.0%であり、C転化率は、200℃で27.2%、250℃で44.3%であった。 Moreover, about the catalyst powder obtained by this comparative example, the performance as an exhaust gas purification catalyst was evaluated by the method similar to Example 1. FIG. As a result, as shown in Table 2, the CO conversion was 63.1% at 200 ° C. and 78.0% at 250 ° C., and the C 3 H 6 conversion was 27.2% at 250 ° C., 250 It was 44.3% at ° C.

[比較例3]
まず、Pt濃度8.486質量%のPt(NH(NO溶液2.381gに純水4mLを加えて金属塩溶液を製造した。この溶液をCe0.9Bi0.120gにスポイトで滴下して含浸させた後、130℃で一晩乾燥させて粉末を得た。この粉末を空気中において500℃で2時間焼成(昇温速度5℃/分)して、1質量%のPtを含むCe0.9Bi0.1粉末を得た。
[Comparative Example 3]
First, 4 mL of pure water was added to 2.381 g of a Pt (NH 3 ) 2 (NO 2 ) 2 solution having a Pt concentration of 8.486% by mass to produce a metal salt solution. The solution was dropped into 20 g of Ce 0.9 Bi 0.1 O 2 with a dropper and impregnated, and then dried at 130 ° C. overnight to obtain a powder. This powder was calcined in air at 500 ° C. for 2 hours (heating rate 5 ° C./min) to obtain Ce 0.9 Bi 0.1 O 2 powder containing 1% by mass of Pt.

このようにして得られた触媒粉末について、実施例1と同様の方法により、排ガス浄化触媒としての性能を評価した。その結果、表2に示すように、CO転化率は、200℃で62.0%、250℃で72.9%であり、C転化率は、200℃で25.7%、250℃で40.4%であった。 With respect to the catalyst powder thus obtained, the performance as an exhaust gas purification catalyst was evaluated by the same method as in Example 1. As a result, as shown in Table 2, the CO conversion was 62.0% at 200 ° C. and 72.9% at 250 ° C., and the C 3 H 6 conversion was 25.7% at 250 ° C. It was 40.4% at ° C.

このように、実施例1および2の触媒粉末では、CO転化率およびC転化率がいずれも担体と比べて大幅に向上しているのがわかった。これは、担体の表面に形成されたPtナノクラスターによって酸化反応が促進されたことによるものであると考えられる。一方、比較例1〜3では、CO転化率およびC転化率がいずれも担体と比べて低い値を示し、担体にPtが担持されたことによって、逆にCO転化率やC転化率が低下する結果となることがわかった。これは、担体自体の活性点とPtの間に何らかの相互作用が起こり、活性点が変質したと考えられる。 Thus, in the catalyst powders of Examples 1 and 2, it was found that both the CO conversion rate and the C 3 H 6 conversion rate were significantly improved as compared with the support. This is considered to be because the oxidation reaction was promoted by the Pt nanoclusters formed on the surface of the support. On the other hand, in Comparative Examples 1 to 3, the CO conversion rate and the C 3 H 6 conversion rate both showed lower values than that of the carrier, and Pt was supported on the carrier, so that the CO conversion rate and C 3 H were reversed. It was found that the 6- conversion rate was reduced. This is considered that some interaction occurred between the active site of the carrier itself and Pt, and the active site was altered.

本発明による触媒の製造方法では、ディーゼルエンジンの排ガス中の一酸化炭素および炭化水素の浄化に適した排ガス浄化触媒として使用可能な触媒の他、化学工学や石油化学などの高温や高圧における触媒反応に使用可能な触媒を製造することができる。   In the method for producing a catalyst according to the present invention, in addition to a catalyst that can be used as an exhaust gas purification catalyst suitable for the purification of carbon monoxide and hydrocarbons in exhaust gas from a diesel engine, a catalytic reaction at high temperatures and high pressures such as chemical engineering and petrochemistry. A usable catalyst can be produced.

本発明による触媒の製造方法の実施の形態を説明する図である。It is a figure explaining embodiment of the manufacturing method of the catalyst by this invention. 実施例1で製造された触媒粉末のTEM写真である。2 is a TEM photograph of the catalyst powder produced in Example 1. 実施例1で製造された触媒粉末のEDXによるナノ粒子の組成分析の結果を示す図である。It is a figure which shows the result of the composition analysis of the nanoparticle by EDX of the catalyst powder manufactured in Example 1. FIG.

符号の説明Explanation of symbols

1 担体
2 貴金属粒子
3 有機分子
4 炭化物
1 Support 2 Precious metal particles 3 Organic molecules 4 Carbide

Claims (5)

CeとBiと酸素を構成元素として含む複合酸化物からなる担体に貴金属粒子を分散して担持させた後、貴金属粒子を有機分子で保護し、その後、不活性ガス雰囲気中で熱処理することを特徴とする、触媒の製造方法。 The noble metal particles are dispersed and supported on a support made of a complex oxide containing Ce, Bi and oxygen as constituent elements, and then the noble metal particles are protected with organic molecules and then heat-treated in an inert gas atmosphere. A method for producing a catalyst. 前記不活性ガス雰囲気中で熱処理した後、水素雰囲気中および空気または酸素雰囲気中の少なくとも一方の雰囲気中で熱処理することを特徴とする、請求項1に記載の触媒の製造方法。 2. The method for producing a catalyst according to claim 1, wherein the heat treatment is performed in at least one of a hydrogen atmosphere and an air or oxygen atmosphere after the heat treatment in the inert gas atmosphere. 前記不活性ガス雰囲気中で熱処理する温度が、前記有機分子を焼成して炭化させる温度であることを特徴とする、請求項1または2に記載の触媒の製造方法。 The method for producing a catalyst according to claim 1 or 2, wherein the temperature of the heat treatment in the inert gas atmosphere is a temperature at which the organic molecules are calcined and carbonized. 前記有機分子が、ポリビニルピロリドン、ポリビニルアルコール、ポリエチレンイミド、ポリアクリル酸、シュウ酸、クエン酸、マレイン酸およびこれらの混合物からなる群から選ばれることを特徴とする、請求項1乃至3のいずれかに記載の触媒の製造方法。 The organic molecule is selected from the group consisting of polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene imide, polyacrylic acid, oxalic acid, citric acid, maleic acid, and a mixture thereof. A process for producing the catalyst as described in 1. above. 前記貴金属粒子が、Pt、PdおよびRhからなる群から選ばれる貴金属の粒子であることを特徴とする、請求項1乃至4のいずれかに記載の触媒の製造方法。
The method for producing a catalyst according to any one of claims 1 to 4, wherein the noble metal particles are noble metal particles selected from the group consisting of Pt, Pd and Rh.
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