JP2006305406A - CATALYST FOR REMOVING NOx IN EXHAUST GAS - Google Patents
CATALYST FOR REMOVING NOx IN EXHAUST GAS Download PDFInfo
- Publication number
- JP2006305406A JP2006305406A JP2005127727A JP2005127727A JP2006305406A JP 2006305406 A JP2006305406 A JP 2006305406A JP 2005127727 A JP2005127727 A JP 2005127727A JP 2005127727 A JP2005127727 A JP 2005127727A JP 2006305406 A JP2006305406 A JP 2006305406A
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- Prior art keywords
- catalyst
- purification
- platinum
- supported
- coated
- Prior art date
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- 239000003054 catalyst Substances 0.000 title claims abstract description 249
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 118
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 56
- 239000011148 porous material Substances 0.000 claims abstract description 51
- 239000002245 particle Substances 0.000 claims abstract description 43
- 238000002844 melting Methods 0.000 claims abstract description 28
- 230000008018 melting Effects 0.000 claims abstract description 28
- 239000012298 atmosphere Substances 0.000 claims abstract description 16
- 239000011248 coating agent Substances 0.000 claims abstract description 12
- 238000000576 coating method Methods 0.000 claims abstract description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 73
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 46
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 44
- 238000000746 purification Methods 0.000 claims description 42
- 239000000377 silicon dioxide Substances 0.000 claims description 30
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 29
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 11
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- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 4
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Abstract
Description
本発明は白金担持触媒を高融点材料で被覆して成る耐熱性排ＮＯｘ浄化用触媒及びこの触媒をモノリス成形体のガス流路内壁に塗布した排ＮＯｘ浄化用モノリス触媒に関するものであり、該排ＮＯｘ浄化用モノリス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を高効率で浄化処理できる。 The present invention relates to discharge the NO x purification for monolithic catalyst coated with heat-resistant exhaust the NO x purification catalyst and the catalyst formed by coating the platinum-supported catalyst of a refractory material in the gas flow passage inner wall of the monolith formed body, the NO x contained in the exhaust gas of a diesel automobile by using exhaust the NO x purification for monolithic catalyst can purify processed with high efficiency.
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。被毒された触媒をそのまま使用し続けると終には、排ガスをまったく処理できなくなるので定期的に再生処理を行う必要がある。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。
Another factor that makes diesel exhaust gas treatment difficult is catalyst poisoning caused by sulfur in the fuel. If the poisoned catalyst continues to be used as it is, the exhaust gas cannot be treated at all. Therefore, it is necessary to periodically perform a regeneration treatment. 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 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. .
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。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及び２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。
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. 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 and 2 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.
しかし、近年の高分子化学の目覚しい進展によって実現されるに至った。簡単にその原理を説明すると、液相で金属前駆物質を親水性の高分子材料でマイクロカプセル化又は被覆することによって安定なコロイドを形成させた後、還元剤存在下で加熱することによってコア成分である金属を析出させる。次にシェル成分の前駆物質を加えて還元、酸化、加水分解等の反応操作を行い、コア-シェル構造の金属ナノ粒子を得ることができる。しかし、前記に述べたように、従来、自動車排ガス浄化用触媒のシンタリング抑制のために上記コア-シェル構造形成技術を応用する考えは提案されていない。
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（国際純正及び応用化学連合）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。
However, it has been realized by remarkable progress in polymer chemistry in recent years. Briefly, the core component is formed by forming a stable colloid by microencapsulating or coating a metal precursor with a hydrophilic polymer material in a liquid phase and then heating in the presence of a reducing agent. To deposit a metal. Next, a precursor of the shell component is added, and reaction operations such as reduction, oxidation, and hydrolysis can be performed to obtain core-shell structured metal nanoparticles. However, as described above, conventionally, the idea of applying the core-shell structure forming technology for suppressing sintering of an automobile exhaust gas purification catalyst has not been proposed.
On the other hand, industrial catalysts are often used in a state of being supported on a porous material. According to IUPAC (International Pure and Applied Chemical Association), the pores of the porous material are classified into micropores with a pore diameter of 2 nm or less, mesopores with 2 to 50 nm, and macropores with 50 nm or more. Yes. 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であり、その比表面積が約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、従来、メソポーラス材料に触媒を担持して成る触媒を触媒活性を維持してその耐熱性シンタリング焼結防止を飛躍的に向上させるための工夫を施したディーゼル排ガス浄化のための効果的な触媒は知られていない。
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する新規の耐熱性担持触媒及びこの触媒をモノリス成形体に塗布したモノリス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 It is an object of the present invention to provide a novel heat-resistant supported catalyst and a monolith catalyst in which this catalyst is applied to a monolith molded article.
本発明者らは上記の目的を達成するために鋭意研究を重ねた結果、高融点材料で表面を特定の被覆したナノサイズの白金系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シンタリング焼結防止できてかつ触媒活性の低下が殆ど見られない驚くべきことを発見し、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、特定の0.3〜50ｎｍの細孔径と特定の100〜1400ｍ2/ｇの比表面積とを有する難溶性の多孔質材料に特定の平均粒径が0.3〜20ｎｍの白金含有主触媒を担持して成る担持触媒を大気中での融点が1000℃以上である高融点材料によって特定の0.3ｎｍ〜10μｍの厚みで被覆した耐熱性排ＮＯｘ浄化用触媒及び該触媒をモノリス成形体のガス流路内壁に塗布した排ＮＯｘ浄化用モノリス触媒を提供するものである。 The present inventors have result of extensive studies to achieve the above object, highly effective nano-sized platinum catalysts identified in a surface coated with a high melting point materials relative to the lean burn exhaust NO x treatment There was a surprising finding that sintering sintering could be prevented even after high temperature treatment and almost no decrease in catalytic activity was observed, and the present invention was completed based on this finding. That is, the present invention relates to a platinum-containing main catalyst having a specific average particle size of 0.3 to 20 nm in a sparingly soluble porous material having a specific pore size of 0.3 to 50 nm and a specific surface area of 100 to 1400 m 2 / g. heat resistance discharge the NO x purification catalyst and the catalyst coated in a thickness of a particular 0.3nm~10μm by refractory material having a supported catalyst formed by supported by the melting point in air 1000 ° C. or more of the monolith formed body there is provided a discharge the NO x purification for monolithic catalyst coated on the gas flow path inner wall.
本発明は、下記（１）から（８）の発明である。
（１） 0.3〜50ｎｍの細孔径と100〜1400ｍ2/ｇの比表面積とを有する難溶性の担体に平均粒径が0.3〜20ｎｍの白金含有主触媒を担持して成る担持触媒を大気中での融点が1000℃以上である高融点材料によって0.3ｎｍ〜10μｍの厚みで被覆したことを特徴とする耐熱性排ＮＯｘ浄化用触媒。
（２） 担体がシリカ、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）記載の耐熱性排ＮＯｘ浄化用触媒。
（３） 高融点材料がシリカ、アルミナ、ジルコニア、チタニア、セリア、イットリア、マグネシア、及びこれらの複合物であることを特徴とする前記（１）及び（2）記載の耐熱性排ＮＯｘ浄化用触媒。
（４） 白金含有主触媒の担持量が0.1〜20質量％であることを特徴とする前記（１）〜（３）記載の耐熱性排ＮＯｘ浄化用触媒。
（５） 前記（１）から（４）の耐熱性排ＮＯｘ浄化用触媒をモノリス成形体のガス流路内壁に塗布したことを特徴とする排ＮＯｘ浄化用モノリス触媒。
（６） モノリス成形体への耐熱性排ＮＯｘ浄化用触媒の塗布量が成形体の3〜30質量％、及びモノリス成形体当たりに換算した白金含有主触媒の坦持量が0.03〜3質量％であることを特徴とする前記（５）記載の排ＮＯｘ浄化用モノリス触媒。
（７） 前記（５）及び（６）の排ＮＯｘ浄化用モノリス触媒を用いた、リッチバーンとリーンバーンを交互に行なう小型ディーゼル用の排ＮＯｘ浄化用モノリス触媒。
（８） 前記（５）及び（６）の排ＮＯｘ浄化用モノリス触媒を用いた、尿素供給システムを搭載する大型ディーゼル用の排ＮＯｘ浄化用モノリス触媒。
The present invention is the following (1) to (8).
(1) A supported catalyst comprising a hardly soluble carrier having a pore diameter of 0.3 to 50 nm and a specific surface area of 100 to 1400 m 2 / g supported on a platinum-containing main catalyst having an average particle diameter of 0.3 to 20 nm in the atmosphere. heat resistance discharge the NO x purification catalyst for melting is equal to or coated with a thickness of 0.3nm~10μm by refractory material that is at 1000 ° C. or higher.
(2) the carrier is silica, alumina, zirconia, titania, and the (1), wherein the heat-resistant exhaust the NO x purification catalyst which is a composite thereof.
(3) a high melting point material is silica, alumina, zirconia, titania, ceria, yttria, magnesia, and the (1) and (2) heat-resistant discharge the NO x purification according which is a composite thereof catalyst.
(4) The electrolyte supported amount of the platinum-containing main catalyst is characterized in that 0.1 to 20% by weight (1) to (3), wherein the heat-resistant exhaust the NO x purification catalyst.
(5) (1) to (4) of heat-resistant exhaust the NO x purification catalyst and is characterized in that applied to the gas flow passage inner wall of the monolith formed body discharge the NO x purification for monolithic catalyst.
(6) 3 to 30 wt% of the coating weight of the heat-resistant exhaust the NO x purification catalyst to the monolith molded body molded body, and the carrying amount of platinum-containing main catalyst as converted per monolith formed body 0.03 to 3 mass wherein which is a% (5) discharging the NO x purification for monolithic catalyst according.
(7) wherein (5) and with discharge the NO x purification for monolithic catalyst of (6), discharging the NO x purification for monolithic catalyst for small diesel performing rich burn and the lean burn alternately.
(8) wherein (5) and (6) of the exhaust NO x using purifying monolithic catalyst, exhaust the NO x purification for monolithic catalyst for a large diesel for mounting a 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処理を低温領域でも極めて効率よく行うことができて長期間効率的に行えるし、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する新規の耐熱性担持触媒及びこの触媒をモノリス成形体に塗布したモノリス触媒を提供することができる。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、本発明のメソポーラスシリカに白金触媒を担持して成る触媒をシリカで被覆した触媒は、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℃での高温酸化処理後でもシンタリング焼結を防止できて酸化処理前の触媒の触媒活性と同程度の高活性を示す。 The exhaust NO x purification catalyst of the present invention can perform diesel exhaust NO x treatment, which has been difficult in the past, extremely efficiently even in a low temperature region, and can be efficiently performed over a long period of time, and a relatively high concentration oxygen atmosphere of lean burn it is possible to provide a monolithic catalyst coated with new refractory supported catalyst and the catalyst on a monolithic molded body to maintain a high activity to a high-temperature exhaust NO x under. For example, a three-way catalyst can hardly purify nitric oxide in an atmosphere with an oxygen concentration of 14%. However, a catalyst in which a catalyst comprising a platinum catalyst supported on mesoporous silica of the present invention is coated with silica has an oxygen concentration of 14%. More than 80% of the nitric oxide coexisting in the atmosphere can be purified at 150-300 ° C, and sintering sintering can be prevented even after high-temperature oxidation treatment at 750 ° C in air, and the catalytic activity of the catalyst before oxidation treatment As high activity as
以下、本発明を詳細に説明する。
本発明の第１の特徴は、白金を主触媒として用いることである。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化学的に安定であるからである。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。
Hereinafter, the present invention will be described in detail.
The first feature of the present invention is to use platinum as the main catalyst. 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 is chemically stable in the high temperature oxygen atmosphere Because. 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.
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。本発明の触媒は担体に担持して用いる。主触媒としての白金の担時量は0.1〜20質量％であり、好ましくは0.1〜10質量％であるが、量的な問題がなければ、通常は、数％の担持量で用いる。担体の触媒担持量は20質量％以上でも可能であるが、担持量が過剰になると反応にほとんど寄与しない細孔深部の触媒が増えるのでよくない。また、0.1質量％未満では活性が十分ではない。 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. The catalyst of the present invention is used by being supported on a carrier. The supported amount of platinum as the main catalyst is 0.1 to 20% by mass, preferably 0.1 to 10% by mass. If there is no quantitative problem, the supported amount is usually several percent. The amount of the catalyst supported on the carrier can be 20% by mass or more, but if the amount supported is excessive, the catalyst in the deep part of the pores that hardly contributes to the reaction increases. Moreover, if it is less than 0.1% by mass, the activity is not sufficient.
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、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、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、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, and these. Can be mentioned.
Among them, chromium becomes passivation film, iron, cobalt, nickel, suction force of the reducing agent is relatively high copper, barium oxide there is the NO x storage properties, cerium oxide having an oxidizing power of the medium and the three manganese dioxide, SO x effective poisoning prevention copper - 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.
本発明の第２の特徴は主触媒を担持するための担体として多孔質材料を用いることである。活性アルミナ及びミクロ細孔を有するゼオライト等の従来使用されている多孔質材料も用いることができるが、近年開発されたメソ細孔を有するメソポーラス材料を用いるのが好ましい。その理由は、メソポーラス材料は貫通型の細孔を持つので触媒の捕捉が強いこと、ネットワーク状に広がった貫通型の細孔構造を通じたガス拡散の効果が期待できること、細孔分布を制御することで触媒活性種の好ましい粒径範囲を維持できること、触媒を細孔内に担持することで触媒粒子の再凝集を抑制し触媒の均一分散を図れること、などの優れた効果があるからである。上記に述べたように、ＮＯｘに対して高活性を示す触媒粒子の粒径はナノサイズであるので、担体の細孔径は触媒粒子と同程度でなければならない。通常、担体の細孔内に担持される触媒の粒径は、細孔径とほぼ同程度であるので、担体の細孔径を制御することによって、好ましい粒径を有するナノ触媒を均一に分散担持することができる。 The second feature of the present invention is that a porous material is used as a support for supporting the main catalyst. Conventionally used porous materials such as activated alumina and zeolite having micropores can also be used, but it is preferable to use mesoporous materials having mesopores developed recently. The reason for this is that mesoporous materials have penetrating pores, so the catalyst is strongly trapped, the effect of gas diffusion through the penetrating pore structure spreading in a network can be expected, and the pore distribution is controlled. This is because the preferable particle diameter range of the catalytically active species can be maintained, and by supporting the catalyst in the pores, reaggregation of the catalyst particles can be suppressed and the catalyst can be uniformly dispersed. As described above, since the particle diameter of the catalyst particles exhibiting high activity with respect to NO x is nano-sized, the pore diameter of the support must be approximately the same as that of the catalyst particles. Normally, the particle size of the catalyst supported in the pores of the carrier is almost the same as the pore size, so that the nano catalyst having a preferred particle size is uniformly dispersed and supported by controlling the pore size of the carrier. be able to.
したがって、担体の細孔径と細孔分布が重要な設計要素であり、比表面積はそれに次ぐ設計要素である。本発明で用いることのできる担体の細孔径は0.3〜50ｎｍの範囲にあり、好ましくは2〜20ｎｍの範囲にある。細孔径が0.3ｎｍ未満であっても触媒の担持は可能であるが不純物等による汚染の影響が大きいのであまり好ましくない。50ｎｍを越えると分散担持された触媒が水熱高温条件などによるシンタリングによって巨大粒子に成長しやすくなるので好ましくない。本発明における細孔径とは、窒素吸着による細孔分布測定によって測定される細孔径のことであり、ＢＪＨ法を用いて得られる細孔分布の微分分布において極大値を示す所の細孔径（直径で表す）を意味する。 Therefore, the pore diameter and pore distribution of the support are important design factors, and the specific surface area is the next design factor. The pore diameter of the carrier that can be used in the present invention is in the range of 0.3 to 50 nm, preferably in the range of 2 to 20 nm. Even if the pore diameter is less than 0.3 nm, the catalyst can be supported, but it is not so preferable because the influence of contamination by impurities and the like is large. If it exceeds 50 nm, the dispersed and supported catalyst tends to grow into large particles by sintering under hydrothermal high temperature conditions, etc., which is not preferable. The pore diameter in the present invention is a pore diameter measured by measuring a pore distribution by nitrogen adsorption, and is a pore diameter (diameter) that shows a maximum value in a differential distribution of the pore distribution obtained by using the BJH method. Means).
比表面積は特別な事情がない限り高ければ高いほどよい。本発明に用いることのできる担体の比表面積は100〜1400ｍ2/ｇであり、好ましくは200〜1200ｍ2/ｇ、さらに好ましくは400〜1200ｍ2/ｇである。比表面積が100ｍ2/ｇ未満では、触媒の担持量が少なくなるので担持触媒の触媒性能はあまり大きくはない。比表面積が1400ｍ2/ｇを越えると材料強度上の問題があるので好ましくない。本発明における比表面積とは、窒素の物理吸着を利用してＢＥＴ式から求められる物質１ｇ当たりの表面積のことである。
本発明で用いる担体材料としては、排ガス中に含まれる高温の水蒸気に対する耐久性の観点から、熱水に難溶性の多孔質材料を用いる。材料の難溶性は、サンプルを150℃の熱水中に1時間置いた時に抽出される物質の重量が0.1％以下であれば実用上問題はない。難溶性の材料として、例えば、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、マグネシア、メタロシリケート（金属酸化物とシリカの固溶体をいう）、及びこれらの複合材料が挙げられる。このなかで、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機械物性が比較的高いので好ましい。
The specific surface area should be as high as possible unless there are special circumstances. The specific surface area of the carrier that can be used in the present invention is 100 to 1400 m 2 / g, preferably 200 to 1200 m 2 / g, more preferably 400 to 1200 m 2 / g. When the specific surface area is less than 100 m 2 / g, the supported amount of the catalyst is reduced, so that the catalyst performance of the supported catalyst is not so great. If the specific surface area exceeds 1400 m 2 / g, there is a problem in material strength, which is not preferable. The specific surface area in the present invention is a surface area per 1 g of a substance obtained from the BET equation using physical adsorption of nitrogen.
As the carrier material used in the present invention, a porous material hardly soluble in hot water is used from the viewpoint of durability against high-temperature water vapor contained in the exhaust gas. The poor solubility of the material has no practical problem if the weight of the substance extracted when the sample is placed in hot water at 150 ° C. for 1 hour is 0.1% or less. Examples of the hardly soluble material include silica, alumina, zirconia, titania, ceria, yttria, niobia, magnesia, metallosilicate (referred to as a solid solution of metal oxide and silica), and composite materials thereof. Of these, silica, alumina, zirconia, titania, and composites thereof are preferable because of their relatively high mechanical properties.
本発明の第３の特徴は、上記担持触媒を高融点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、600℃以下であるので、還元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、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、主触媒を担持したメソポーラス触媒を高融点材料で被覆すると非常に効果的であることがわかった。 The third feature of the present invention is that the supported catalyst is coated with a high melting point material. Since the exhaust gas temperature of diesel engines is usually 600 ° C or less, there is almost no risk of the main catalyst platinum particles being sintered in a reducing atmosphere, but it removes poisonous substances such as sulfur adsorbed on the catalyst surface. Therefore, when heat treatment is performed at 750 to 850 ° C. in an oxidizing atmosphere, sintering occurs because it is oxidized to a low melting point oxide. 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. Thus, as a result of intensive investigations of measures for preventing sintering, it has been found that it is very effective to coat a mesoporous catalyst carrying a main catalyst with a high melting point material.
本発明における高融点材料は、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、セリア、イットリア、マグネシア、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 high melting point 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 the 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, ceria, yttria, magnesia, and a composite thereof are preferable because they have a high sintering suppressing effect on the main catalyst.
本発明の高融点材料による被覆は、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高融点材料の種類に依存するが、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、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。
本発明で用いる担体の合成法は、従来の方法を用いて所用の材料を製造することができる。例えば、界面活性剤をメソ細孔のテンプレートとして用いる従来の方法（例えば、特許文献1、2、及び3）に準じて製造することができる。この方法では、担体の前駆物質には、通常、金属アルコキシドを用いる。
In the coating with the high melting point material of the present invention, when the thickness of the coating layer is too thick, the permeability and diffusibility of the exhaust gas are low, resulting in a decrease in the activity of the main catalyst. Easy to destroy. Therefore, the thickness of the coating had to be determined empirically. Although the preferable thickness calculated | required by experiment depends on the kind of high melting-point material, the range of 0.3 nm-10 micrometers is preferable normally. In the case of alumina, zirconia, or the like having a dense structure, the thickness may be in the range of 0.3 to 50 nm. However, silica having many structural voids, various zeolites, cordierite, and the like have good exhaust gas permeability even at a thickness of 1 μm.
As a method for synthesizing the carrier used in the present invention, a desired material can be produced using a conventional method. For example, it can be produced according to a conventional method using a surfactant as a template for mesopores (for example, Patent Documents 1, 2, and 3). In this method, a metal alkoxide is usually used as a support precursor.
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、水系溶媒が好ましい。
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。
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 aqueous 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.
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、前駆物質のモル比が0.01〜0.60、好ましくは0.02〜0.50、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/主剤のモル比が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。反応性生物は通常、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、500〜1000℃の高温で熱分解することによって完全除去し、メソポーラス材料を得ることができる。 The composition of the reaction system comprising the precursor, surfactant, solvent and stabilizer is such that the molar ratio of the precursor is 0.01 to 0.60, preferably 0.02 to 0.50, and the molar ratio of the precursor / surfactant is 1 to 30, preferably Is 1 to 10, the solvent / surfactant molar ratio is 1 to 1000, preferably 5 to 500, and the stabilizer / main agent molar ratio 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. Reactive organisms are usually separated by filtration, thoroughly washed with water, dried, and then extracted with an organic solvent such as alcohol, followed by thermal decomposition at a high temperature of 500 to 1000 ° C. It can be completely removed to obtain a mesoporous material.
本発明の担持触媒の製造方法は、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、担体に触媒の前駆物質を溶解した溶液を吸収させるか又は触媒の前駆物質を溶解した水溶液に担体を浸漬後、乾燥させた後、還元剤によってメソ担体の細孔に存在する触媒の前駆物質を金属に還元し、担持触媒とすることができる。白金触媒の前駆物質として、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。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。 The method for producing a supported catalyst of the present invention can produce a required catalyst by applying a conventional method. For example, after absorbing the solution in which the catalyst precursor is dissolved in the support or by immersing the support in an aqueous solution in which the catalyst precursor is dissolved and then drying, the precursor of the catalyst present in the pores of the meso support by the reducing agent. The substance can be reduced to a metal to form a supported catalyst. As precursors of the platinum catalyst, for example, H2PtCl 4, (NH 4) 2PtCl 4, H2PtCl6, (NH 4) 2PtCl 6, Pt (NH 3) 4 (NO 3) 2, Pt (NH 3) 4 (OH) 2 PtCl 4 , platinum acetylacetonate, and the like can be used. 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.
本発明の高融点材料で被覆された担持触媒は通常の方法で製造することができる。例えば、高融点材料の前駆物質として金属アルコキシド等を用い、この加水分解によって担持触媒を被覆する場合には、担持触媒に高融点材料の前駆物質を溶解した溶液を吸収させるか又は高融点材料の前駆物質を溶解した溶液に担持触媒を所望の時間浸漬後、濾過し、洗浄、乾燥を行って製造することができる。他の操作方法としては、担持触媒を高融点材料の前駆物質の溶液に浸漬、濾過、所望の時間放置後、洗浄、乾燥することによって製造することができる。
高融点材料の前駆物質が塩類などの場合には、担持触媒に吸収されるか又は吸着した高融点材料の前駆物質を加水分解処理、酸化処理、還元処理、加熱処理、等の所要の反応操作を行うことによって製造することができる。高融点材料の前駆物質としては、例えば、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、ホウ素、炭素、珪素、スカンジウム、イットリウム、セリウム、錫、バリウム、亜鉛、アルミニウム、カルシウム、マグネシウム、ランタン、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、担持触媒/高融点材料の前駆物質の質量比は、通常10〜1000であり、好ましくは50〜100、主触媒の前駆物質/高融点材料の前駆物質の質量比は通常0.1〜1000、好ましくは1〜100である。
The supported catalyst coated with the high melting point material of the present invention can be produced by a usual method. For example, when a metal alkoxide or the like is used as a precursor of a high melting point material and the supported catalyst is coated by hydrolysis, a solution in which the precursor of the high melting point material is dissolved in the supported catalyst is absorbed, or The supported catalyst can be produced by immersing the supported catalyst in a solution in which the precursor is dissolved, filtering, washing and drying. As another method of operation, the supported catalyst can be produced by immersing it in a solution of a precursor of a high melting point material, filtering, leaving it for a desired time, washing and drying.
When the precursor of the high melting point material is a salt or the like, the required reaction operation such as hydrolysis, oxidation, reduction, or heat treatment of the precursor of the high melting point material absorbed or adsorbed by the supported catalyst. Can be manufactured. For example, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel, copper, boron, carbon , Silicon, scandium, yttrium, cerium, tin, barium, zinc, aluminum, calcium, magnesium, lanthanum, gadolinium, and other water-soluble chlorides, nitrates, sulfates, carbonates, acetates, ammonia complexes, alkoxides, etc. 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 mass ratio of the supported catalyst / high melting point material precursor is usually 10 to 1000, preferably 50 to 100, and the main catalyst precursor / high melting point material precursor mass ratio is usually 0.1 to 100. 1000, preferably 1-100.
本発明の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。本発明のモノリス触媒とは、高融点材料で被覆して成る担持触媒をモノリス成形体のガス流路内壁に塗布した触媒を意味している。高融点材料で被覆して成る担持触媒の塗布量は、3〜30質量％が好ましい。30％を超える塗布は、担体内部に存在する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触媒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 monolith molded body of the present invention is a molded body in which a cross section of the molded body is mesh-shaped and provided with gas flow paths partitioned by thin walls in parallel to the axial direction. The outer shape of the molded body is usually a cylindrical shape. The monolith catalyst of the present invention means a catalyst obtained by coating a supported catalyst formed by coating with a high melting point material on the inner wall of a gas flow path of a monolith molded body. The coating amount of the supported catalyst formed by coating with a high melting point material is preferably 3 to 30% by mass. Application exceeding 30% is not preferable because gas diffusion to the catalyst existing inside the carrier is slow. Moreover, if it is 3% or less, the catalyst performance is not sufficient. The adhesion amount corresponding to the coating amount of the catalyst on the monolith molded body is preferably 0.03 to 3% by mass of the molded body.
本発明のモノリス触媒は、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製造することができる。例えば、高融点材料で被覆して成る担持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、モノリス成形体に担体を塗布したのち、触媒原料を担体に含浸し、還元処理、熱処理を行った後、高融点材料で被覆する方法によっても製造することができる。成形体に塗布した高融点材料被覆担持触媒層の厚みは、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。 The monolith catalyst of this invention can be manufactured according to the manufacturing method of the monolith molded object which adhered the three-way catalyst for motor vehicles. For example, a mixture prepared by mixing a supported catalyst coated with a high-melting-point material and colloidal silica as a binder at a mass ratio of 1: (0.01-0.2) is usually prepared, and the mixture is dispersed in water to usually 10-50. After adjusting the mass% slurry, the monolith molded body 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, under an inert atmosphere such as nitrogen, helium, argon, etc. It can be manufactured by heat treatment at 1000 ° C for several hours. As a binder other than colloidal silica, methyl cellulose, acrylic resin, polyethylene glycol, or the like can be used as appropriate. As another method, it can also be produced by a method in which a support is applied to a monolith molded article, and then a catalyst raw material is impregnated in the support, subjected to reduction treatment and heat treatment, and then coated with a high melting point material. The thickness of the high melting point material-coated supported catalyst layer applied to the molded body is usually preferably 1 μm to 100 μm, and particularly preferably 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.
本発明のモノリス触媒は、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。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モノリス触媒を用いると、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。 Monolith catalyst of the present invention, 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. Since the oxygen concentration is high at the time of rich burn and the oxygen concentration is low at the time of lean burn, when the monolith catalyst of the present invention is used for exhaust gas purification treatment of a small diesel that can perform rich burn and lean burn alternately, 150 to efficiently exhaust NO x can be purified processed in wide temperature range of 700 ° 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径（直径で表す）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。
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. Most of the synthesized carriers showed a peak at the position of a specific pore diameter (expressed by 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.
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 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/メソポーラスシリカ］触媒の合成
容積1リットルのビーカーに、蒸留水300ｇ、エタノール240ｇ、及びドデシルアミン30ｇを入れ、溶解させた。攪拌下でテトラエトキシシラン125ｇを加えて室温で22時間攪拌した。生成物を濾過、水洗し、110℃で5時間温風乾燥した後、空気中で750℃5時間焼成して含有するドデシルアミンを分解除去し、メソポーラスシリカ材料を得た。細孔分布及び比表面積測定の結果、約2 nmの位置に細孔ピークがあり、比表面積が871 m2/g、細孔容積が0.63 cm3/g、2〜50 nmの細孔が占める容積は0.63 cm3/gであった。得られたメソポーラスシリカ3ｇと〔Pt(NH3)4〕Cl2・3Ｈ2Ｏ 0.119ｇを溶解した水溶液10ｇを蒸発皿に入れ、スチームバスで蒸発乾固した後、真空乾燥機に入れ100℃３時間真空乾燥を行った。この試料を石英管に入れ、ヘリウム希釈水素ガス（10v/v％）気流下750℃で3時間還元し、白金の含有量が約2質量％の担持触媒を合成した。坦持された白金粒子の平均粒径は約2.0 nmであった。次に、得られた担持触媒3ｇをテトラエトキシシラン30ｇに浸漬し、室温で24時間放置後、濾過、エタノール洗浄、100℃３時間真空乾燥を行い、窒素気流中で750℃３時間加熱処理を行った。つまり、担持触媒を被覆したシリカの前駆体が熱によって脱水縮合して被覆シリカになります。シリカ被覆［白金/メソポーラスシリカ］触媒を合成した。シリカ膜の厚みは約100 nmであった。
Example 1 Synthesis of Silica-Coated [Platinum / Mesoporous Silica] Catalyst 300 g of distilled water, 240 g of ethanol, and 30 g of dodecylamine were placed in a 1 liter beaker and dissolved. Under stirring, 125 g of tetraethoxysilane was added and stirred at room temperature for 22 hours. The product was filtered, washed with water, dried in warm air at 110 ° C. for 5 hours, and then calcined in air at 750 ° C. for 5 hours to decompose and remove contained dodecylamine to obtain a mesoporous silica material. As a result of pore distribution and specific surface area measurement, there is a pore peak at a position of about 2 nm, the specific surface area is 871 m 2 / g, the pore volume is 0.63 cm 3 / g, and the pores are 2 to 50 nm. The volume was 0.63 cm 3 / g. 10 g of an aqueous solution in which 3 g of the obtained mesoporous silica and 0.119 g of [Pt (NH 3 ) 4 ] Cl 2 .3H 2 O are dissolved is placed in an evaporating dish, evaporated to dryness in a steam bath, and then placed in a vacuum dryer at 100 ° C. Vacuum drying was performed for 3 hours. This sample was placed in a quartz tube and reduced at 750 ° C. for 3 hours under a helium-diluted hydrogen gas (10 v / v%) stream to synthesize a supported catalyst having a platinum content of about 2% by mass. The average particle size of the supported platinum particles was about 2.0 nm. Next, 3 g of the obtained supported catalyst was immersed in 30 g of tetraethoxysilane, left at room temperature for 24 hours, filtered, washed with ethanol, dried in vacuum at 100 ° C for 3 hours, and heat-treated in a nitrogen stream at 750 ° C for 3 hours. went. In other words, the silica precursor coated with the supported catalyst is dehydrated and condensed by heat to become coated silica. Silica-coated [platinum / mesoporous silica] catalyst was synthesized. The thickness of the silica film was about 100 nm.
「実施例２」アルミナ被覆［白金/メソポーラスアルミナ］触媒の合成
メソポーラスアルミナは非特許文献［Applied Catalysis A: general 254 (2003) 339-343.］に記載の方法に従って以下のように合成した。すなわち、1モルのアルミニウムイソプロポキシドをエタノール：イソプロパノール＝8：6の混合液100ｇに加え、攪拌下40-50℃に加熱し溶解させる。これにテトラエチレングリコール1モルを加えて、室温で攪拌下、2モルの蒸留水を滴下した。室温で10時間静置した後、80℃で10時間置いた。生成したゲルをオートクレーブに入れ160℃で4時間加熱した後、生成した固形物を取り出し、空気中で750℃5時間焼成した。得られたメソポーラスアルミナは約3ｎｍの位置に細孔ピークがあり、比表面積は380 m2/g、細孔容積は0.50 cm3/g、2〜50 nmの細孔が占める容積は0.48 cm3/gであった。このメソポーラスアルミナ3ｇと〔Pt(NH3)4〕Cl2・3Ｈ2Ｏ 0.119ｇを溶解した水溶液10ｇを蒸発皿に入れ、スチームバスで蒸発乾固した後、真空乾燥機に入れ100℃３時間真空乾燥を行った。この試料を石英管に入れ、ヘリウム希釈水素ガス（10v/v％）気流下750℃で3時間還元し、白金の含有量が約2質量％の担持触媒を合成した。メソポーラス触媒に坦持された白金粒子の平均粒径は約3 nmであった。次に、得られたメソポーラス触媒3ｇを1質量％のアルミニウムイソプロポキシドのイソプロパノール溶液30ｇに浸漬し、室温で10分放置後、濾過、イソプロパノール洗浄、100℃３時間真空乾燥を行い、窒素気流中で750℃３時間加熱処理を行い前駆体を熱によって脱水縮合して、アルミナ被覆［白金/メソポーラスアルミナ］触媒を合成した。アルミナ膜の厚みは約10ｎｍであった。
Example 2 Synthesis of Alumina-Coated [Platinum / Mesoporous Alumina] Catalyst Mesoporous alumina was synthesized as follows according to the method described in Non-Patent Document [Applied Catalysis A: general 254 (2003) 339-343.]. That is, 1 mol of aluminum isopropoxide is added to 100 g of a mixed solution of ethanol: isopropanol = 8: 6, and heated to 40-50 ° C. with stirring to dissolve. 1 mol of tetraethylene glycol was added thereto, and 2 mol of distilled water was added dropwise with stirring at room temperature. The mixture was allowed to stand at room temperature for 10 hours and then at 80 ° C. for 10 hours. The produced gel was put in an autoclave and heated at 160 ° C. for 4 hours, and then the produced solid was taken out and baked in air at 750 ° C. for 5 hours. The obtained mesoporous alumina has a pore peak at a position of about 3 nm, a specific surface area of 380 m 2 / g, a pore volume of 0.50 cm 3 / g, and a volume occupied by pores of 2 to 50 nm is 0.48 cm 3 / g. 10 g of an aqueous solution in which 3 g of mesoporous alumina and 0.119 g of [Pt (NH 3 ) 4 ] Cl 2 .3H 2 O are dissolved is placed in an evaporating dish and evaporated to dryness in a steam bath, and then placed in a vacuum dryer at 100 ° C. for 3 hours. Vacuum drying was performed. This sample was placed in a quartz tube and reduced at 750 ° C. for 3 hours under a helium-diluted hydrogen gas (10 v / v%) stream to synthesize a supported catalyst having a platinum content of about 2% by mass. The average particle size of the platinum particles supported on the mesoporous catalyst was about 3 nm. Next, 3 g of the obtained mesoporous catalyst was immersed in 30 g of an isopropanol solution of 1% by mass of aluminum isopropoxide, allowed to stand at room temperature for 10 minutes, filtered, washed with isopropanol, and vacuum dried at 100 ° C. for 3 hours in a nitrogen stream. The precursor was dehydrated and condensed by heat at 750 ° C. for 3 hours to synthesize an alumina-coated [platinum / mesoporous alumina] catalyst. The thickness of the alumina film was about 10 nm.
「実施例３」ジルコニア被覆［白金/メソポーラスジルコニア］触媒の合成
容積1リットルのビーカーに蒸留水210ｍＬ、エタノール114ｍＬ、及び1-ヘキサデシルトリメチルアミンブロマイド32.7ｇを入れ、攪拌下、これに、70質量％ジルコニウムテトラプロポキシドのプロパノール溶液140.1ｇ、エタノール150ｍＬ、及びアセチルアセトン12ｍＬの混合溶液を滴下した。室温で2時間攪拌後、80℃で48時間静置した。これをステンレスのオートクレーブに移し、160℃で24時間攪拌してスラリー状の沈殿物を得た。該沈殿物を濾過し、水洗して、80℃で乾燥した後、0.1規定塩酸酸性のエタノール溶液によってテンプレートを抽出除去した。次いで110℃で１時間真空乾燥し、白色の微粉末を30ｇ得た。これを石英管に入れ、窒素ガス気流下で750℃1時間処理した。得られたメソポーラスジルコニアは約2.5ｎｍの位置に細孔ピークがあり、比表面積は120 m2/g、細孔容積は0.30 cm3/g、2〜50 nmの細孔が占める容積は0.30 cm3/gであった。このメソポーラスジルコニア3ｇと〔Pt(NH3)4〕Cl2・3Ｈ2Ｏ 0.119ｇを溶解した水溶液10ｇを蒸発皿に入れ、スチームバスで蒸発乾固した後、真空乾燥機に入れ100℃３時間真空乾燥を行った。この試料を石英管に入れ、ヘリウム希釈水素ガス（10v/v％）気流下750℃で3時間還元し、白金の含有量が約2質量％の担持触媒を合成した。メソポーラス触媒に坦持された白金粒子の平均粒径は約2.5 nmであった。次に、得られたメソポーラス触媒3ｇを1質量％のジルコニウムプロポキシドのプロパノール溶液30ｇに浸漬し、室温で5分放置後、濾過、プロパノール洗浄、100℃３時間真空乾燥を行い、窒素気流中で750℃３時間加熱処理を行い前駆体を熱によって脱水縮合して、ジルコニア被覆［白金/メソポーラスジルコニア］触媒を合成した。ジルコニア膜の厚みは約5ｎｍであった。
[Example 3] Synthesis of zirconia-coated [platinum / mesoporous zirconia] catalyst 210 mL of distilled water, 114 mL of ethanol, and 32.7 g of 1-hexadecyltrimethylamine bromide were placed in a beaker having a volume of 1 liter, and 70% by mass with stirring. A mixed solution of 140.1 g of zirconium tetrapropoxide in propanol, 150 mL of ethanol, and 12 mL of acetylacetone was added dropwise. The mixture was stirred at room temperature for 2 hours and then allowed to stand at 80 ° C. for 48 hours. This was transferred to a stainless steel autoclave and stirred at 160 ° C. for 24 hours to obtain a slurry-like precipitate. The precipitate was filtered, washed with water, dried at 80 ° C., and then the template was extracted and removed with a 0.1 N hydrochloric acid acidic ethanol solution. Subsequently, it vacuum-dried at 110 degreeC for 1 hour, and obtained 30g of white fine powder. This was put into a quartz tube and treated at 750 ° C. for 1 hour under a nitrogen gas stream. The obtained mesoporous zirconia has a pore peak at a position of about 2.5 nm, a specific surface area of 120 m 2 / g, a pore volume of 0.30 cm 3 / g, and a volume occupied by pores of 2 to 50 nm is 0.30 cm. 3 / g. 10 g of an aqueous solution in which 3 g of this mesoporous zirconia and 0.119 g of [Pt (NH 3 ) 4 ] Cl 2 · 3H 2 O are dissolved is placed in an evaporating dish, evaporated to dryness in a steam bath, and then placed in a vacuum dryer at 100 ° C. for 3 hours. Vacuum drying was performed. This sample was placed in a quartz tube and reduced at 750 ° C. for 3 hours under a helium-diluted hydrogen gas (10 v / v%) stream to synthesize a supported catalyst having a platinum content of about 2% by mass. The average particle size of the platinum particles supported on the mesoporous catalyst was about 2.5 nm. Next, 3 g of the obtained mesoporous catalyst was immersed in 30 g of a 1% by weight zirconium propoxide propanol solution, allowed to stand at room temperature for 5 minutes, filtered, washed with propanol, and vacuum-dried at 100 ° C. for 3 hours. A heat treatment was performed at 750 ° C. for 3 hours, and the precursor was dehydrated and condensed by heat to synthesize a zirconia-coated [platinum / mesoporous zirconia] catalyst. The thickness of the zirconia film was about 5 nm.
「実施例４」チタニア被覆［白金/メソポーラスチタニア］触媒の合成
容積1リットルのビーカーに蒸留水210ｍＬ、エタノール114ｍＬ、及び1-ヘキサデシルトリメチルアミンブロマイド32.7ｇを入れ、攪拌下、これに、70質量％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140.1ｇ、エタノール150ｍＬ、及びアセチルアセトン12ｍＬの混合溶液を滴下した。室温で2時間攪拌後、80℃で48時間静置した。これをステンレスのオートクレーブに移し、160℃で24時間攪拌してスラリー状の沈殿物を得た。該沈殿物を濾過し、水洗して、80℃で乾燥した後、0.1規定塩酸酸性のエタノール溶液によってテンプレートを抽出除去した。次いで110℃で１時間真空乾燥し、白色の微粉末を30ｇ得た。これを石英管に入れ、窒素ガス気流下で750℃1時間処理した。得られたメソポーラスチタニアは約2.5ｎｍの位置に細孔ピークがあり、比表面積は120 m2/g、細孔容積は0.30 cm3/g、2〜50 nmの細孔が占める容積は0.30 cm3/gであった。このメソポーラスチタニア3ｇと〔Pt(NH3)4〕Cl2・3Ｈ2Ｏ 0.119ｇを溶解した水溶液10ｇを蒸発皿に入れ、スチームバスで蒸発乾固した後、真空乾燥機に入れ100℃３時間真空乾燥を行った。この試料を石英管に入れ、ヘリウム希釈水素ガス（10v/v％）気流下750℃で3時間還元し、白金の含有量が約2質量％の担持触媒を合成した。坦持された白金粒子の平均粒径は約2.5 nmであった。次に、得られた担持触媒3ｇを1質量％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30ｇに浸漬し、室温で5分放置後、濾過、イソプロパノール洗浄、100℃３時間真空乾燥を行い、窒素気流中で750℃３時間加熱処理を行い、チタニア被覆［白金/メソポーラスチタニア］触媒を合成した。チタニア膜の厚みは約5ｎｍであった。
Example 4 Synthesis of titania-coated [platinum / mesoporous titania] catalyst In a 1-liter beaker, 210 mL of distilled water, 114 mL of ethanol, and 32.7 g of 1-hexadecyltrimethylamine bromide were added, and 70% by mass with stirring. A mixed solution of 140.1 g of isopropanol solution of titanium tetraisopropoxide, 150 mL of ethanol, and 12 mL of acetylacetone was added dropwise. The mixture was stirred at room temperature for 2 hours and then allowed to stand at 80 ° C. for 48 hours. This was transferred to a stainless steel autoclave and stirred at 160 ° C. for 24 hours to obtain a slurry-like precipitate. The precipitate was filtered, washed with water, dried at 80 ° C., and then the template was extracted and removed with a 0.1 N hydrochloric acid acidic ethanol solution. Subsequently, it vacuum-dried at 110 degreeC for 1 hour, and obtained 30g of white fine powder. This was put into a quartz tube and treated at 750 ° C. for 1 hour under a nitrogen gas stream. The obtained mesoporous titania has a pore peak at a position of about 2.5 nm, a specific surface area of 120 m 2 / g, a pore volume of 0.30 cm 3 / g, and a volume occupied by pores of 2 to 50 nm is 0.30 cm. 3 / g. 10 g of an aqueous solution in which 3 g of this mesoporous titania and 0.119 g of [Pt (NH 3 ) 4 ] Cl 2 · 3H 2 O are dissolved is placed in an evaporating dish, evaporated to dryness in a steam bath, and then placed in a vacuum dryer at 100 ° C. for 3 hours. Vacuum drying was performed. This sample was put in a quartz tube and reduced at 750 ° C. for 3 hours in a helium-diluted hydrogen gas (10 v / v%) stream to synthesize a supported catalyst having a platinum content of about 2% by mass. The average particle size of the supported platinum particles was about 2.5 nm. Next, 3 g of the obtained supported catalyst was immersed in 30 g of an isopropanol solution of 1% by mass of titanium tetraisopropoxide, allowed to stand at room temperature for 5 minutes, filtered, washed with isopropanol, and vacuum-dried at 100 ° C. for 3 hours. In this, heat treatment was performed at 750 ° C. for 3 hours to synthesize a titania-coated [platinum / mesoporous titania] catalyst. The thickness of the titania film was about 5 nm.
「比較例２」
比較例１の触媒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。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0.2質量％であった。
“Comparative Example 2”
1 g of the catalyst of Comparative 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 and air-dried, and then heat-treated in a nitrogen stream at 750 ° C. for 3 hours. The amount of the catalyst adhered was about 10% by mass of the mini-molded product, and the amount of platinum supported per mini-molded product was about 0.2% by mass.
「実施例５」シリカ被覆［白金/メソポーラスシリカ］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/メソポーラスシリカ］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。シリカ被覆担持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0.2質量％であった。
[Example 5] Synthesis of monolith catalyst coated with silica-coated [platinum / mesoporous silica] catalyst 1 g of silica-coated [platinum / mesoporous silica] catalyst of Example 1 and 0.1 g of colloidal silica were added to 10 ml of distilled water and stirred. The slurry was adjusted. 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 and air-dried, and then heat-treated in a nitrogen stream at 750 ° C. for 3 hours. The amount of the silica-coated supported catalyst was about 10% by mass of the mini-molded product, and the amount of platinum supported per mini-molded product was about 0.2% by mass.
「実施例６」アルミナ被覆［白金/メソポーラスアルミナ］触媒を塗布したモノリス触媒の合成
実施例２のアルミナ被覆［白金/メソポーラスアルミナ］触媒1ｇを用いて実施例4と同様の方法でアルミナ被覆［白金/メソポーラスアルミナ］触媒を塗布したモノリス触媒を合成した。アルミナ被覆担持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0.2質量％であった。
「実施例７」ジルコニア被覆［白金/メソポーラスジルコニア］触媒を塗布したモノリス触媒の合成
実施例3のジルコニア被覆［白金/メソポーラスジルコニア］触媒1ｇを用いて実施例4と同様の方法でジルコニア被覆［白金/メソポーラスジルコニア］触媒を塗布したモノリス触媒を合成した。ジルコニア被覆担持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0.2質量％であった。
Example 6 Synthesis of Monolith Catalyst Coated with Alumina-Coated [Platinum / Mesoporous Alumina] Catalyst Alumina-coated [Platinum] in the same manner as in Example 4 using 1 g of the alumina-coated [platinum / mesoporous alumina] catalyst of Example 2. / Mesoporous alumina] A monolithic catalyst coated with a catalyst was synthesized. The adhesion amount of the alumina-coated supported catalyst was about 10% by mass of the mini-molded product, and the supported amount of platinum per mini-molded product was about 0.2% by mass.
[Example 7] Synthesis of monolith catalyst coated with zirconia-coated [platinum / mesoporous zirconia] catalyst Zirconia-coated [platinum] in the same manner as in Example 4 using 1 g of the zirconia-coated [platinum / mesoporous zirconia] catalyst of Example 3 / Mesoporous zirconia] monolithic catalyst coated with catalyst was synthesized. The amount of the zirconia-coated supported catalyst was about 10% by mass of the mini-molded product, and the amount of platinum supported per mini-molded product was about 0.2% by mass.
「実施例８」チタニア被覆［白金/メソポーラスチタニア］触媒を塗布したモノリス触媒の合成
実施例４のチタニア被覆［白金/メソポーラスチタニア］触媒1ｇを用いて実施例4と同様の方法でチタニア被覆［白金/メソポーラスチタニア］触媒を塗布したモノリス触媒を合成した。チタニア被覆担持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0.2質量％であった。
[Example 8] Synthesis of monolith catalyst coated with titania-coated [platinum / mesoporous titania] catalyst Titania-coated [platinum] in the same manner as in Example 4 using 1 g of the titania-coated [platinum / mesoporous titania] catalyst of Example 4 / Mesoporous titania] Monolith catalyst coated with catalyst was synthesized. The adhesion amount of the titania-coated supported catalyst was about 10% by mass of the mini-molded product, and the supported amount of platinum per mini-molded product was about 0.2% by mass.
「比較例３」還元剤としてエチレンを用いたＮＯｘ処理
比較例２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。
Comparative Example 3 NO x Treatment Using Ethylene as Reducing Agent 0.60 g of the catalyst sample of Comparative Example 2 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, a catalyst obtained by heat-treating the same catalyst sample in air at 750 ° C. for 24 hours was 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９〜１２」還元剤としてエチレンを用いたＮＯｘ処理
実施例５〜８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0.60 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、本発明の高融点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/メソポーラスシリカ］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 9 to 12” NO x treatment using ethylene as a reducing agent Each of the catalyst samples of Examples 5 to 8 was filled in a continuous flow reaction tube made of quartz in an amount of 0.60 g, and the concentration of nitric oxide was adjusted with helium. 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, a catalyst obtained by heat-treating the same catalyst sample in air at 750 ° C. for 24 hours was 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 high melting point material of the present invention is a fresh catalyst even after treatment 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 / mesoporous silica] catalyst enabled efficient NO x purification at 150 to 300 ° C., which is not 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１３」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の触媒を6ｇ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、本発明のモノリス触媒は、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。
It was treated with nitric oxide using 6g of catalyst of the NO x process Example 5 for rich burn using ethylene as "Example 13" reducing agent. 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, it can be seen that the monolith catalyst of the present invention can efficiently purify NO x under rich burn conditions from a medium temperature region to a high temperature region using a hydrocarbon as a reducing agent. 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１４」還元剤としてアンモニアを用いたＮＯｘ処理
実施例５の触媒を6ｇ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に示したように、本発明の触媒はアンモニアを還元剤として用いても、高濃度酸素共存下において１５０〜６００℃の広い温度範囲で８０％以上のＮＯｘ処理率を与えることができる。 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。
“Example 14” NO x treatment using ammonia as a reducing agent 6 g of the catalyst of Example 5 was used to treat nitric oxide. 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. As shown in Table 3, the catalyst of the present invention can give a NO x treatment rate of 80% or more in a wide temperature range of 150 to 600 ° C. in the presence of high concentration oxygen even when ammonia is used as a 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.
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処理を低温領域でも極めて効率よく行うことができて長期間効率的に行えるし、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する新規の耐熱性担持触媒及びこの触媒をモノリス成形体に塗布したモノリス触媒を提供することができる。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、本発明のメソポーラスシリカに白金触媒を担持して成る触媒をシリカで被覆した触媒は、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℃での酸化処理後でも酸化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 example, the exhaust NO x purification catalyst of the present invention can perform the diesel exhaust NO x treatment, which has been difficult in the past, extremely efficiently even in a low temperature region, and can be efficiently performed over a long period of time. relatively high concentrations novel thermostable supported catalyst and the catalyst to maintain a high activity to a high-temperature exhaust NO x in an oxygen atmosphere it is possible to provide a monolithic catalyst coated on the monolith formed body. For example, a three-way catalyst can hardly purify nitric oxide in an atmosphere with an oxygen concentration of 14%. However, a catalyst in which a catalyst comprising a platinum catalyst supported on mesoporous silica of the present invention is coated with silica has an oxygen concentration of 14%. More than 80% of the nitric oxide coexisting in the atmosphere can be purified at 150-300 ° C, and even after oxidation at 750 ° C in air, it showed high activity comparable to that of the catalyst before oxidation .
本発明の担持触媒及びモノリス触媒は、ディーゼル排ＮＯｘ浄化用触媒として有用である。 Supported catalysts and monolithic catalyst of the present invention is useful as a diesel exhaust the NO x purification catalyst.
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| JP2010000446A (en) * | 2008-06-20 | 2010-01-07 | Asahi Kasei Corp | Catalyst for purifying lean burn exhaust gas |
| JP2010065250A (en) * | 2008-09-09 | 2010-03-25 | Hiroshima Univ | Method for producing composite body, and composite body |
| JP2010510082A (en) * | 2006-11-22 | 2010-04-02 | 本田技研工業株式会社 | Method for changing the properties of a composition, method for adjusting the performance of a catalytic material, and composition |
| US8182753B2 (en) * | 2006-05-12 | 2012-05-22 | Emitec Gesellschaft Fuer Emissionstechnologie Mbh | Carrier body for exhaust-gas aftertreatment with dispersed catalyst configuration, process for producing a carrier body and exhaust gas treatment unit and vehicle having a carrier body |
| JP2013111530A (en) * | 2011-11-29 | 2013-06-10 | Toshiba Corp | Catalyst for hydrolyzing plant-based material and method for producing sugar using the catalyst |
| JP2016203172A (en) * | 2011-03-03 | 2016-12-08 | ユミコア・アクチエンゲゼルシャフト・ウント・コムパニー・コマンディットゲゼルシャフトＵｍｉｃｏｒｅ ＡＧ ＆ Ｃｏ．ＫＧ | Catalyst activation material for performing the selective catalyst reduction of nitrogen oxide, and catalyst converter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US8182753B2 (en) * | 2006-05-12 | 2012-05-22 | Emitec Gesellschaft Fuer Emissionstechnologie Mbh | Carrier body for exhaust-gas aftertreatment with dispersed catalyst configuration, process for producing a carrier body and exhaust gas treatment unit and vehicle having a carrier body |
| JP2010510082A (en) * | 2006-11-22 | 2010-04-02 | 本田技研工業株式会社 | Method for changing the properties of a composition, method for adjusting the performance of a catalytic material, and composition |
| JP2008200653A (en) * | 2007-02-22 | 2008-09-04 | Asahi Kasei Corp | New exhaust gas cleaning method |
| JP2010000446A (en) * | 2008-06-20 | 2010-01-07 | Asahi Kasei Corp | Catalyst for purifying lean burn exhaust gas |
| JP2010065250A (en) * | 2008-09-09 | 2010-03-25 | Hiroshima Univ | Method for producing composite body, and composite body |
| JP2016203172A (en) * | 2011-03-03 | 2016-12-08 | ユミコア・アクチエンゲゼルシャフト・ウント・コムパニー・コマンディットゲゼルシャフトＵｍｉｃｏｒｅ ＡＧ ＆ Ｃｏ．ＫＧ | Catalyst activation material for performing the selective catalyst reduction of nitrogen oxide, and catalyst converter |
| JP2013111530A (en) * | 2011-11-29 | 2013-06-10 | Toshiba Corp | Catalyst for hydrolyzing plant-based material and method for producing sugar using the catalyst |
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