JP4600710B2 - Exhaust gas purification catalyst - Google Patents
Exhaust gas purification catalyst Download PDFInfo
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- JP4600710B2 JP4600710B2 JP2000372119A JP2000372119A JP4600710B2 JP 4600710 B2 JP4600710 B2 JP 4600710B2 JP 2000372119 A JP2000372119 A JP 2000372119A JP 2000372119 A JP2000372119 A JP 2000372119A JP 4600710 B2 JP4600710 B2 JP 4600710B2
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- noble metal
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- 239000003054 catalyst Substances 0.000 title claims description 58
- 238000000746 purification Methods 0.000 title claims description 23
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- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Catalysts (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、排気ガス浄化用触媒に係り、更に詳細には、内燃機関のエンジン始動直後から３５０℃以下の酸素過剰雰囲気下において、排気ガスを浄化し、特に排気ガス中の炭化水素、一酸化炭素及び有機溶媒可溶成分を高効率で浄化する排気ガス浄化用触媒に関するものである。
【０００２】
【従来の技術】
従来から、内燃機関の排気ガス中の炭化水素（ＨＣ）、一酸化炭素（ＣＯ）等の浄化を目的に、貴金属を浄化成分に用いた排気ガス浄化用触媒が開発されている。特に、ディーゼルエンジン排気ガス中のＨＣ、ＣＯ及び有機溶媒可溶成分（ＳＯＦ）の浄化を目的として、ガソリン車で使われているような通常のモノリス型触媒の開発が進められている。
【０００３】
一般に、ディーゼルエンジン排気ガス浄化用触媒としては、（１）ＨＣ、ＣＯのほかＳＯＦなどの有害成分の低温からの浄化除去効率が高いこと、（２）燃料として用いる軽油中に多量に含まれる硫黄成分から発生する二酸化硫黄（ＳＯ２）の三酸化硫黄（ＳＯ３）への酸化能が低く、且つサルフェート（二酸化硫黄が酸化されて三酸化硫黄や硫酸ミストになったもの）の生成が抑制できること、（３）活性成分の硫黄成分による性能低下が小さいこと、（４）触媒表面に粒子状物質が付着した場合でも性能低下が小さいこと、（５）高負荷での連続運転下でも耐えられる、いわゆる高温耐久性が高いこと、という性能を有する触媒が望まれている。
【０００４】
また、従来から、ＨＣ、ＣＯ及びＳＯＦ、炭素系粒子状物質などの燃焼除去効率を高める目的で種々の提案がなされている。例えば、特開昭５５−２４５９７号公報には、白金族元素系触媒として、ロジウム（７．５％）白金合金、白金／パラジウム（５０／５０）混合物、酸化タンタルまたは酸化セリウム上にパラジウムを担持したもの、更にはパラジウムと７５％以下の白金とから成る合金等が開示されている。
【０００５】
その他に、特開昭６１−１２９０３０号公報、特開昭６１−１４９２２２号公報及び特開昭６１−１４６３１４号公報には、パラジウムとロジウムとを主な活性成分とし、さらに、アルカリ金属、アルカリ土類金属、銅、ランタン、亜鉛及びマンガンなどを添加した触媒組成物が開示され、また、特開昭５９−８２９４４号公報には、銅、アルカリ金属、モリブデン又はバナジウム及びこれらの任意の組み合せに係る金属とを組合せた触媒組成物が開示されている。
【０００６】
【発明が解決しようとする課題】
しかしながら、上述のような従来の触媒は、ディーゼルエンジン排気ガスの低温・酸素過剰雰囲気下におけるＨＣ、ＣＯ及びＳＯＦの除去、低温域で微粒子状物質が付着した際の活性低下の抑制、又は硫黄による活性成分の性能低下抑制などが不十分であるという課題があった。即ち、ディーゼルエンジン排気ガス浄化用触媒として、ＨＣ、ＣＯ及びＳＯＦを高効率で浄化できる触媒は未だ見出されていない。
【０００７】
本発明は、このような従来技術の有する課題に鑑みてなされたものであり、その目的とするところは、ディーゼルエンジン排気ガスを始めとする内燃機関の排気ガス中のＨＣ、ＣＯ及びＳＯＦを効率良く浄化できる排気ガス浄化用触媒を提供することにある。
【０００８】
【課題を解決するための手段】
本発明者らは、上記課題を解決すべく鋭意検討を行った結果、特定の耐熱性無機酸化物担体上に、異なる粒径の貴金属粒子を混在させることにより、上記課題が解決できることを見出し、本発明を完成するに至った。
【０００９】
即ち、本発明の排気ガス浄化用触媒は、一体構造型担体上に触媒成分を被覆して成る排気ガス浄化用触媒であって、上記触媒成分が、ＨＣ吸着材と、耐熱性無機酸化物担体に担持された貴金属とを含有し、上記耐熱性無機酸化物担体が、式：Ｗ Ｘ Ｚｒ １−Ｘ Ｏ ２ （式中のＷはタングステン、Ｘは０．０５〜０．２５を示す）及び式：Ｓ Ｘ Ｚｒ １−Ｘ Ｏ ２ （式中のＳは硫黄、Ｘは０．０５〜０．２５を示す）で表されるジルコニウム酸化物、並びにアナターゼ型構造を含む１００ｎｍ以下の粒径を有するチタニウム酸化物から成る群から選ばれる少なくとも１種の酸化物を含有して成り、上記貴金属は、貴金属塩の水溶液にクエン酸、酢酸及び蓚酸から成る群より選ばれた少なくとも１種の有機酸を含有させ、貴金属と有機酸のモル比（有機酸の総モル数／貴金属のモル数）を０．２５〜２．０として耐熱性無機酸化物担体に担持されていると共に、粒径の異なる貴金属粒子が混在していることを特徴とする。
【００１０】
また、本発明の排気ガス浄化用触媒の好適形態は、上記貴金属の粒径が、直径１ｎｍ以上５ｎｍ未満である小粒子と、５ｎｍ以上２０ｎｍ以下である大粒子を含むことを特徴とする。
【００１２】
【発明の実施の形態】
以下、本発明について詳細に説明する。なお、「％」は特記しない限り、質量百分率を示す。
本発明の排気ガス浄化用触媒は、一体構造型担体上に触媒成分を被覆して成る。
この触媒成分は、ＨＣ吸着材と、耐熱性無機酸化物担体に担持された貴金属とを含有し、この貴金属としては、白金（Ｐｔ）、パラジウム（Ｐｄ）やロジウム（Ｒｈ）等が挙げられ、これら貴金属は、排気ガス中のＣＯ、ＨＣ、窒素酸化物（ＮＯｘ）やＳＯＦ成分等の酸化還元反応を促進する。特に、ディーゼルエンジン排気ガス浄化用触媒においては、Ｐｔを用いることが好ましい。
【００１３】
上記貴金属は、微粒子の形で上記耐熱性無機酸化物に担持されているが、この粒子には異なる粒径のものが混在しており、小粒子（ＤＳ）と大粒子（ＤＬ）に分けることができる。透過型電子顕微鏡（ＴＥＭ）による測定で、粒径が１ｎｍ以上５ｎｍ未満の粒子をＤＳ、５ｎｍ以上２０ｎｍ以下の粒子をＤＬとし、これらが分散担持されていることが好ましい。
このように、上記耐熱性無機酸化物担体上にＤＳとＤＬを共存させることにより、ＤＳ上では、ＣＯの酸化反応が起こりやすく、ＤＬでは未燃焼ＨＣの酸化反応が起こりやすくなる。
【００１４】
また、上記耐熱性無機酸化物担体にＤＳとＤＬが担持された状態で、ＴＥＭでＤＳとＤＬによって占められる面積を測定したときに、ＤＳの総面積／ＤＬの総面積＝１／４〜４／１であることが好ましい。即ち、上記耐熱性無機酸化物担体を上から見て平面上に貴金属粒子を投影した場合のＤＳとＤＬの総面積比、更に言い換えれば、ＤＳとＤＬを球冠状に切断した場合のＤＳとＤＬの総断面積比が１／４〜４／１であることが好ましい。ＤＳとＤＬとの面積比が上記範囲をはずれると、低温・酸素過剰雰囲気下におけるＨＣ、ＣＯ及びＳＯＦの除去効率が低下してしまうことがある。
具体的には、ＤＳ／ＤＬが１／４未満では、ＤＳが少ないため、ＨＣ・ＣＯ浄化は主にＤＬ上で行われると推察され、十分なＨＣ・ＣＯ浄化性能が発揮されない。ＤＳ／ＤＬが１／１では、ＤＳ上とＤＬ上の両方でＨＣ・ＣＯ浄化が行われ、且つＤＬがヒートスポットとなり、排気ガスが低温で触媒が暖まりにくくても、浄化活性を保つことができる。また、ＤＳ／ＤＬが４／１を超えると、ＤＬに対しＤＳが多すぎて、ＤＬのヒートスポット効果が薄れてしまい、触媒が暖まりにくく、十分なＨＣ・ＣＯ浄化性能が得られないことがある。
【００１５】
また、上記触媒成分は、上述の如く、ＨＣ吸着材も含有し、エンジン始動直後から２００℃以下の低温域では、このＨＣ吸着材に優先的に液状のＳＯＦが捕捉される。また、上記触媒成分中にこのＨＣ吸着材と上記貴金属粒子が共存することにより、上記貴金属粒子上にＳＯＦが吸着してしまうのを防止して貴金属粒子の活性開始の悪化を抑制することができるとともに、上記Ｐｔ等の貴金属と未燃焼ＨＣ及びＣＯとの浄化反応の発現を促進することができる。
更に、未燃焼のＨＣの酸化反応が起こるＤＬは、ヒートスポットとなり、上記ＨＣ吸着材に捕捉されたＳＯＦの酸化反応を促進することができると推測される。 このように、触媒中にＨＣ、ＣＯ及びＳＯＦの酸化反応が発現しやすい反応場を設けることにより、低温・酸素過剰雰囲気下においてもＨＣ、ＣＯ及びＳＯＦを効率良く除去できる。
【００１６】
また、上記ＨＣ吸着材は、ＺＳＭ５、モルデナイト、ＵＳＹ又はβ−ゼオライト及びこれらの任意の組み合わせに係るゼオライトであることが好ましい。エンジン始動直後から２００℃以下の低温域でも、液状のＳＯＦを優先的にＨＣ吸着材に捕捉させることができる。
更に、上記ゼオライトの含有率は、該触媒成分の５０％〜９０％であることが好ましい。含有率が５０％未満ではＨＣ吸着材としての効果が十分に発現せず、９０％を越えるとＨＣ吸着材としての効果が飽和し、これ以上増量しても効果が上がらないことがある。また、該含有率の範囲内にあれば、ＳＯＦの捕捉効率を上げ、上記Ｐｔ等の貴金属粒子上へのＳＯＦを吸着を抑制し、上記貴金属とＣＯ・未燃焼ＨＣとの浄化反応を促進することができる。
【００１７】
また、上記触媒成分に含有される該耐熱性無機酸化物担体は、ジルコニウム酸化物及び／又は後述するようなチタニウム酸化物を含有して成るものが用いられる。具体的には、次式（１）
ＷＸＺｒ１−ＸＯ２ ・・・ （１）
（式中のＷはタングステン、Ｘは０．０５〜０．２５を示す）
で表されるジルコニウム酸化物とすることができる。Ｘは０．０５〜０．２５が好ましく、０．０５未満ではＷの効果が十分に発現せず、逆に、０．２５を越えるとＷの効果が飽和してしまうことがある。
更に、上記耐熱性無機酸化物担体は、次式（２）
ＳＸＺｒ１−ＸＯ２ ・・・ （２）
（式中のＳは硫黄、Ｘは０．０５〜０．２５を示す）
で表されるジルコニウム酸化物を用いることもでき、これらのジルコニウム酸化物を混合して用いてもかまわない。Ｘは式（１）のジルコニウム酸化物と同様、０．０５〜０．２５が好ましく、０．０５未満ではＳの効果が十分に発現せず、逆に、０．２５を越えるとＳの効果が飽和してしまうことがある。
上記耐熱性無機酸化物担体にこれらのジルコニウム酸化物を用いることにより、低温・酸素過剰雰囲気下であっても、活性点であるＰｔ等の貴金属粒子上に吸着し難いＨＣ成分を、優先的に吸着させ、酸化除去することができる。
【００１８】
更に、上記耐熱性無機酸化物担体は、アナターゼ型構造を含む粒径１００ｎｍ以下のチタニウム酸化物（二酸化チタン）を用いることもでき、該チタニウム酸化物の５０％以上がアナターゼ型構造であることが好ましい。チタニウム酸化物を用いることにより、低温・酸素過剰雰囲気下において、活性点であるＰｔ等の貴金属粒子上でＣＯの低温酸化・除去できる。また、粒径が１００ｎｍを越えると酸化チタンの低温ＣＯ酸化反応の促進効果が低下し、アナターゼ型構造の含有率が５０％未満になると低温ＣＯ酸化反応の促進効果が低下してしまうことがある。
【００１９】
本発明の排気ガス浄化用触媒を製造するに当たり、上記耐火性無機酸化物担体に上記貴金属を担持する際に、水溶性貴金属塩の水溶液に、クエン酸、酢酸又は蓚酸及びこれらの任意の組み合わせに係る有機酸を含有させ、上記貴金属と該有機酸のモル比が、有機酸の総モル数／貴金属のモル数＝０．２５〜２．０であることが好ましい。
上記耐火性無機酸化物担体に貴金属粒子を担持させるには、通常、貴金属の水溶液を作り、それを上記耐火性無機酸化物担体にしみ込ませてから乾燥、焼成し、貴金属だけを残す方法が採られる。上記モル比で上記貴金属水溶液に該有機酸を含有させると、上述のＤＳとＤＬの面積比が１／４〜４／１になるように貴金属の担持をコントロールできる。上記モル比が２．０を越えると有機酸の分解燃焼時の発熱が大きく、貴金属粒子径の分布が所定の範囲に設定できず、０．２５未満では有機酸の効果が十分に発現せず、同様に貴金属粒子径の分布が所定の範囲に設定できないことがある。
【００２０】
また、上記触媒成分の総担持量は、耐火性モノリス担体１リットル当たり、１０〜３５０ｇ／Ｌが好ましく、さらに、上記ＨＣ吸着材の担持量は５〜２００ｇ／Ｌ、上記耐熱性無機酸化物担体の担持量は１〜２００ｇ／Ｌ、上記貴金属の担持量は０．１〜１０ｇ／Ｌであることが好ましい。
【００２１】
なお、上記一体構造型担体には、耐熱性材料から成る担体構造体が好ましく、例えばセラミック製のオープンフロー又はウォールフローの担体構造体、ＳｉＣ製担体やメタル製担体でも使用できる。
【００２２】
【実施例】
以下、本発明を実施例及び比較例により更に詳細に説明するが、本発明はこれら実施例に限定されるものではない。
【００２３】
（実施例１）
平均粒子径が３０ｎｍの酸化チタン（アナターゼ型構造が８０％以上）粉末に、ジニトロジアンミン酸白金とクエン酸を溶解した水溶液（有機酸の総モル数／白金モル数＝１．０）を含浸し、１５０℃で２４時間乾燥した後、３００℃で１時間、次いで、６００℃で１時間焼成し、Ｐｔ担持酸化チタン粉末（粉末ａ）を得た。この粉末ａのＰｔ濃度は１５．０％であった。
上記Ｐｔ担持酸化チタン粉末（粉末ａ）２６７ｇ、β−ゼオライト粉末１０００ｇ、活性アルミナ粉末４８３ｇ、硝酸酸性アルミナゾル５０ｇ（ベーマイトアルミナ１０％に１０％の硝酸を添加することによって得られたゾル）及び純水２０００ｇを磁性ボールミルに投入し、混合粉砕してスラリー液を得た。このスラリー液をコージェライト質モノリス担体（４００セル／８ミル、１．３Ｌ）に付着させ、空気流にてセル内の余剰のスラリーを取り除いて乾燥し、４００℃で１時間焼成し、コート層重量１８０ｇ／Ｌになるまでコーティング作業を繰り返し、本例の触媒−ａを得た。
【００２４】
（実施例２）
平均粒子径が３０ｎｍの酸化チタン（アナターゼ型構造が８０％以上）粉末に、ジニトロジアンミン酸白金とクエン酸を溶解した水溶液（有機酸の総モル数／白金モル数＝１．０）を含浸し、１５０℃で２４時間乾燥した後、３００℃で１時間、次いで、６００℃で１時間焼成し、Ｐｔ担持酸化チタン粉末（粉末ｂ）を得た。この粉末ｂのＰｔ濃度は５．０％であった。
上記Ｐｔ担持酸化チタン粉末（粉末ｂ）８００ｇ、β−ゼオライト粉末９８０ｇ、硝酸酸性アルミナゾル２０ｇ（ベーマイトアルミナ１０％に１０％の硝酸を添加することによって得られたゾル）及び純水２０００ｇを磁性ボールミルに投入し、混合粉砕してスラリー液を得た。このスラリー液をコージェライト質モノリス担体（４００セル／８ミル、１．３Ｌ）に付着させ、空気流にてセル内の余剰のスラリーを取り除いて乾燥し、４００℃で１時間焼成し、コート層重量１８０ｇ／Ｌになるまでコーティング作業を繰り返し、本例の触媒−ｂを得た。
【００２５】
（実施例３）
有機酸の総モル数／白金モル数＝１．５とした以外は、実施例１と同様の操作を繰り返し、本例の触媒−ｃを得た。
【００２６】
（実施例４）
有機酸の総モル数／白金モル数＝２．０とした以外は、実施例１と同様の操作を繰り返し、本例の触媒−ｄを得た。
【００２７】
（実施例５）
有機酸の総モル数／白金モル数＝０．５とした以外は、実施例１と同様の操作を繰り返し、本例の触媒−ｅを得た。
【００２８】
（実施例６）
平均粒子径が３０ｎｍの酸化チタン（アナターゼ型構造が８０％以上）粉末の代わりに、Ｗ０．１Ｚｒ０．９Ｏ２粉末を用い、ジニトロジアンミン酸白金とクエン酸を溶解した水溶液（有機酸の総モル数／白金モル数＝１．０）を含浸し、１５０℃で２４時間乾燥した後、３００℃で１時間、次いで、６００℃で１時間焼成し、Ｐｔ担持酸化ジルコニウム粉末（粉末ｃ）を得た。この粉末ｃのＰｔ濃度は１５．０％であった。
上記Ｐｔ担持酸化ジルコニウム粉末（粉末ｃ）２６７ｇ、β−ゼオライト粉末１０００ｇ、活性アルミナ粉末４８３ｇ、硝酸酸性アルミナゾル５０ｇ（ベーマイトアルミナ１０％に１０％の硝酸を添加することによって得られたゾル）及び純水２０００ｇを磁性ボールミルに投入し、混合粉砕してスラリー液を得た。このスラリー液をコージェライト質モノリス担体（４００セル／８ミル、１．３Ｌ）に付着させ、空気流にてセル内の余剰のスラリーを取り除いて乾燥し、４００℃で１時間焼成し、コート層重量１８０ｇ／Ｌになるまでコーティング作業を繰り返し、本例の触媒−ｆを得た。
【００２９】
（実施例７）
Ｗ０．１Ｚｒ０．９Ｏ２粉末の代わりに、Ｓ０．１Ｚｒ０．９Ｏ２粉末を用いた以外は、実施例６と同様の操作を繰り返して、本例の触媒−ｇを得た。
【００３０】
（実施例８）
β−ゼオライト粉末１０００ｇの代わりに、β−ゼオライト粉末７００ｇ、ＺＳＭ５粉末３００ｇを用いた以外は、実施例１と同様の操作を繰り返して、本例の触媒−ｈを得た。
【００３１】
（実施例９）
β−ゼオライト粉末１０００ｇの代わりに、β−ゼオライト粉末４００ｇ、モルデナイト粉末２００ｇ、ＺＳＭ５粉末２００ｇ、ＵＳＹ粉末２００ｇを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｉを得た。
【００３２】
（実施例１０）
粉末ａ２６７ｇの代わりに、粉末ａ１３４ｇとＰｔ１５．０％担持ＺｒＯ２粉末１３４ｇを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｊを得た。
【００３３】
（実施例１１）
粉末ａ２６７ｇの代わりに、粉末ａ１３４ｇとＰｔ１５．０％担持Ｗ０．１Ｚｒ０．９Ｏ２粉末１３４ｇを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｋを得た。
【００３４】
（実施例１２）
粉末ａ２６７ｇの代わりに、粉末ａ１３４ｇとＰｔ１５．０％担持Ｓ０．１Ｚｒ０．９Ｏ２粉末１３４ｇを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｌを得た。
【００３５】
（実施例１３）
粉末ａの代わりに、粉末ａ２２０ｇ、Ｐｔ１．０％担持β−ゼオライト粉末７００ｇを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｍを得た。
【００３６】
（実施例１４）
β−ゼオライト粉末１０００ｇの代わりに、β−ゼオライト粉末７００ｇを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｎを得た。
【００３７】
（実施例１５）
β−ゼオライト粉末１０００ｇの代わりに、β−ゼオライト粉末１５００ｇを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｏを得た。
【００３８】
（実施例１６）
クエン酸の代わりに酢酸を用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｐを得た。
【００３９】
（実施例１７）
クエン酸の代わりに蓚酸を用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｑを得た。
【００４０】
（実施例１８）
平均粒径１００ｎｍの酸化チタンを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｒを得た。
【００４１】
（比較例１）
β−ゼオライトを用いなかった以外は、実施例１と同様の操作を行い、本例の触媒−ａａを得た。
【００４２】
（比較例２）
粉末ａ２６７ｇの代わりにＰｔ１５％担持β−ゼオライト２６７ｇを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｂｂを得た。
【００４３】
（比較例３）
有機酸を用いなかった以外は、実施例１と同様の操作を行い、本例の触媒−ｃｃを得た。
【００４４】
（比較例４）
有機酸の総モル数／白金モル数＝１０とした以外は、実施例１と同様の操作を行い、本例の触媒−ｄｄを得た。
【００４５】
（比較例５）
平均粒径１００ｎｍ、ルチル型構造の酸化チタンを用いた以外は、実施例１と同様の操作を行い、本例の触媒−ｅｅを得た。
【００４６】
上記各実施例及び比較例の排気ガス浄化用触媒の仕様を表１に示した。
【００４７】
【表１】
上記各実施例及び比較例について、図１の評価システムを用いて、下記評価条件でＨＣ、ＣＯの浄化特性評価（欧州のＥＣＥ＋ＥＵＤＣ）を行った。
【００４９】
＜耐久条件＞
エンジン排気量 ２５００ｃｃ
燃料 ＪＩＳ２号軽油
触媒入口ガス温度 ６００℃
耐久時間 １００時間
【００５０】
＜性能評価条件＞
触媒容量 触媒１．３Ｌ
評価車両 日産自動車株式会社製 Ｖ型６気筒 ２．５Ｌディーゼルエンジン
【００５１】
また、ＨＣ及びＣＯの浄化率については、次式▲３▼及び▲４▼
ＨＣ浄化率（％）
＝（[触媒入口ＨＣ濃度]−[触媒出口ＨＣ濃度]）／[触媒入口ＨＣ濃度]×１００…▲３▼
ＣＯ浄化率（％）
＝（[触媒入口ＣＯ濃度]−[触媒出口ＣＯ濃度]）／[触媒入口ＣＯ濃度]×１００…▲４▼
で示される式で求め、その結果を表２に示した。
【００５２】
【表２】
上記各実施例は、上記各比較例と比べて、いずれも触媒活性が高く、未燃焼ＨＣ、ＣＯ及びＳＯＦの低温からの浄化性能に優れ、ディーゼルエンジン排気ガス浄化用触媒として、ＨＣ、ＣＯ及びＳＯＦを高効率で浄化することができることが確認できた。
【００５４】
【発明の効果】
本発明の触媒は、特定の耐熱性無機酸化物担体上に、異なる粒径の貴金属粒子を混在させることとしたため、ディーゼルエンジン排気ガスを始めとする内燃機関の排気ガス中のＨＣ、ＣＯ及びＳＯＦを効率良く浄化できる触媒を提供することができる。
【図面の簡単な説明】
【図１】排気ガス浄化用触媒の評価システムを示すシステム構成図である。
【符号の説明】
１ エンジン
２ 触媒[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purifying catalyst, and more particularly, purifies exhaust gas in an oxygen-excess atmosphere of 350 ° C. or less immediately after engine startup of an internal combustion engine, particularly hydrocarbons and monoxide in the exhaust gas. The present invention relates to an exhaust gas purifying catalyst that purifies carbon and organic solvent soluble components with high efficiency.
[0002]
[Prior art]
Conventionally, exhaust gas purification catalysts using precious metals as purification components have been developed for the purpose of purifying hydrocarbons (HC), carbon monoxide (CO), and the like in exhaust gas of internal combustion engines. In particular, for the purpose of purifying HC, CO and organic solvent soluble components (SOF) in diesel engine exhaust gas, development of a normal monolith type catalyst used in a gasoline vehicle is underway.
[0003]
In general, the diesel engine exhaust gas purification catalyst has (1) high purification and removal efficiency of toxic components such as SOF as well as HC and CO from low temperature, and (2) sulfur contained in a large amount in light oil used as fuel. The ability of sulfur dioxide (SO 2 ) generated from the components to be oxidized to sulfur trioxide (SO 3 ) is low, and the generation of sulfate (sulfur dioxide oxidized to sulfur trioxide or sulfuric acid mist) can be suppressed. (3) The performance degradation due to the sulfur component of the active component is small, (4) The performance degradation is small even when particulate matter adheres to the catalyst surface, (5) It can withstand even under continuous operation at high load, A catalyst having the performance of so-called high-temperature durability is desired.
[0004]
Conventionally, various proposals have been made for the purpose of improving the combustion removal efficiency of HC, CO and SOF, carbon-based particulate matter, and the like. For example, in Japanese Patent Application Laid-Open No. 55-24597, palladium is supported on a rhodium (7.5%) platinum alloy, a platinum / palladium (50/50) mixture, tantalum oxide or cerium oxide as a platinum group element-based catalyst. And alloys made of palladium and 75% or less of platinum are disclosed.
[0005]
In addition, JP-A-61-129030, JP-A-61-149222, and JP-A-61-146314 contain palladium and rhodium as main active ingredients, and further, alkali metals, alkaline earths. A catalyst composition to which a metal, copper, lanthanum, zinc, manganese and the like are added is disclosed, and JP-A-59-82944 relates to copper, alkali metal, molybdenum or vanadium and any combination thereof. A catalyst composition in combination with a metal is disclosed.
[0006]
[Problems to be solved by the invention]
However, conventional catalysts such as those described above remove HC, CO, and SOF from diesel engine exhaust gas in a low-temperature, oxygen-excess atmosphere, suppress the decrease in activity when particulate matter adheres in a low-temperature region, or are due to sulfur. There was a problem that the performance degradation of the active ingredient was insufficiently suppressed. That is, as a diesel engine exhaust gas purifying catalyst, a catalyst capable of purifying HC, CO and SOF with high efficiency has not been found yet.
[0007]
The present invention has been made in view of such problems of the prior art, and an object of the present invention is to efficiently use HC, CO, and SOF in exhaust gas of an internal combustion engine such as diesel engine exhaust gas. An object of the present invention is to provide an exhaust gas purification catalyst that can be well purified.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by mixing noble metal particles having different particle diameters on a specific heat-resistant inorganic oxide support, The present invention has been completed.
[0009]
That is, the exhaust gas purification catalyst of the present invention is an exhaust gas purification catalyst obtained by coating a catalyst component on a monolithic structure type carrier, and the catalyst component includes an HC adsorbent, a heat-resistant inorganic oxide carrier, and the like. And the above heat-resistant inorganic oxide support has the formula: W X Zr 1-X O 2 (W is tungsten, X is 0.05 to 0.25) and A particle size of 100 nm or less including a zirconium oxide represented by the formula: S X Zr 1-X O 2 (wherein S represents sulfur and X represents 0.05 to 0.25) and an anatase type structure. And at least one organic acid selected from the group consisting of citric acid, acetic acid and oxalic acid in an aqueous solution of a noble metal salt. The molar ratio of noble metal to organic acid The total number of moles of organic acid / noble metal molar number) as 0.25 to 2.0 with being supported on heat-resistant inorganic oxide support, characterized in that the different particle sizes noble metal particles are mixed .
[0010]
In addition, a preferred embodiment of the exhaust gas purifying catalyst of the present invention is characterized in that the particle size of the noble metal includes small particles having a diameter of 1 nm to less than 5 nm and large particles having a diameter of 5 nm to 20 nm.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. “%” Indicates a mass percentage unless otherwise specified.
The exhaust gas purifying catalyst of the present invention is formed by coating a catalyst component on an integral structure type carrier.
This catalyst component contains an HC adsorbent and a noble metal supported on a heat-resistant inorganic oxide carrier. Examples of the noble metal include platinum (Pt), palladium (Pd), rhodium (Rh), and the like. These noble metals promote redox reactions such as CO, HC, nitrogen oxides (NOx) and SOF components in the exhaust gas. In particular, it is preferable to use Pt in a diesel engine exhaust gas purification catalyst.
[0013]
The precious metal is supported on the heat-resistant inorganic oxide in the form of fine particles, but these particles have different particle sizes and are divided into small particles (DS) and large particles (DL). Can do. As measured by a transmission electron microscope (TEM), it is preferable that particles having a particle diameter of 1 nm or more and less than 5 nm are represented by DS, and particles having a particle diameter of 5 nm or more and 20 nm or less are represented by DL, and these are dispersedly supported.
Thus, by allowing DS and DL to coexist on the above heat-resistant inorganic oxide carrier, an oxidation reaction of CO easily occurs on DS, and an oxidation reaction of unburned HC easily occurs on DL.
[0014]
Further, when the area occupied by DS and DL is measured by TEM in a state where DS and DL are supported on the heat-resistant inorganic oxide support, the total area of DS / total area of DL = 1/4 to 4 / 1 is preferable. That is, the total area ratio of DS and DL when the noble metal particles are projected on a plane when the heat-resistant inorganic oxide support is viewed from above, more specifically, DS and DL when DS and DL are cut into a spherical crown shape. The total cross-sectional area ratio is preferably ¼ to 4/1. If the area ratio of DS and DL is out of the above range, the removal efficiency of HC, CO, and SOF in a low temperature / oxygen excess atmosphere may decrease.
Specifically, when DS / DL is less than 1/4, since DS is small, it is assumed that HC / CO purification is mainly performed on DL, and sufficient HC / CO purification performance is not exhibited. When DS / DL is 1/1, HC / CO purification is performed on both DS and DL, and DL becomes a heat spot, and even if the exhaust gas is low temperature and the catalyst is difficult to warm, the purification activity can be maintained. it can. Further, when DS / DL exceeds 4/1, there are too many DSs with respect to DL, the heat spot effect of DL is diminished, the catalyst is difficult to warm, and sufficient HC / CO purification performance cannot be obtained. is there.
[0015]
Further, as described above, the catalyst component also contains an HC adsorbent, and liquid SOF is preferentially captured by the HC adsorbent in a low temperature range of 200 ° C. or less immediately after the engine is started. Further, the coexistence of the HC adsorbent and the noble metal particles in the catalyst component can prevent the SOF from adsorbing on the noble metal particles and suppress the deterioration of the activation start of the noble metal particles. At the same time, it is possible to promote the expression of the purification reaction between the noble metal such as Pt and the unburned HC and CO.
Furthermore, it is presumed that DL in which oxidation reaction of unburned HC occurs becomes a heat spot and can promote the oxidation reaction of SOF trapped in the HC adsorbent. As described above, by providing a reaction field in the catalyst in which an oxidation reaction of HC, CO, and SOF easily occurs, HC, CO, and SOF can be efficiently removed even in a low temperature / oxygen excess atmosphere.
[0016]
The HC adsorbent is preferably ZSM5, mordenite, USY or β-zeolite and a zeolite related to any combination thereof. Even in a low temperature range of 200 ° C. or less immediately after the engine is started, liquid SOF can be preferentially captured by the HC adsorbent.
Furthermore, the content of the zeolite is preferably 50% to 90% of the catalyst component. When the content is less than 50%, the effect as an HC adsorbent is not sufficiently exhibited. When the content exceeds 90%, the effect as an HC adsorbent is saturated, and even if the amount is increased further, the effect may not be improved. If the content is within the range, the SOF trapping efficiency is increased, the adsorption of SOF onto noble metal particles such as Pt is suppressed, and the purification reaction between the noble metal and CO / unburned HC is promoted. be able to.
[0017]
Further, the heat-resistant inorganic oxide carrier contained in the catalyst component is one containing zirconium oxide and / or titanium oxide as described later. Specifically, the following formula (1)
W X Zr 1-X O 2 (1)
(W in the formula represents tungsten, and X represents 0.05 to 0.25)
It can be set as the zirconium oxide represented by these. X is preferably 0.05 to 0.25. If W is less than 0.05, the effect of W is not sufficiently exhibited. Conversely, if it exceeds 0.25, the effect of W may be saturated.
Further, the heat-resistant inorganic oxide carrier has the following formula (2)
S X Zr 1-X O 2 (2)
(In the formula, S represents sulfur and X represents 0.05 to 0.25)
Or a mixture of these zirconium oxides may be used. X is preferably 0.05 to 0.25 as in the case of the zirconium oxide of formula (1), and if it is less than 0.05, the effect of S is not sufficiently exhibited. May become saturated.
By using these zirconium oxides in the heat-resistant inorganic oxide support, HC components that are difficult to adsorb on precious metal particles such as Pt, which are active sites, are preferentially used even in a low temperature / oxygen-rich atmosphere. It can be adsorbed and removed by oxidation.
[0018]
Furthermore, the heat-resistant inorganic oxide support, can also be used a particle diameter 100nm or less of titanium oxide containing anatase structure (titanium dioxide), that over 50% of the titanium oxide is anatase structure preferable. By using titanium oxide, CO can be oxidized and removed at low temperature on noble metal particles such as Pt which are active sites in a low temperature / oxygen-rich atmosphere. Further, when the particle size exceeds 100 nm, the promotion effect of the low temperature CO oxidation reaction of titanium oxide is lowered, and when the content of the anatase structure is less than 50%, the promotion effect of the low temperature CO oxidation reaction may be lowered. .
[0019]
In producing the exhaust gas purifying catalyst of the present invention, when the noble metal is supported on the refractory inorganic oxide support, an aqueous solution of a water-soluble noble metal salt is added to citric acid, acetic acid or oxalic acid and any combination thereof. The organic acid is contained, and the molar ratio of the noble metal to the organic acid is preferably the total number of moles of organic acid / number of moles of noble metal = 0.25 to 2.0.
In order to support the noble metal particles on the refractory inorganic oxide support, a method is generally employed in which an aqueous solution of noble metal is prepared, soaked in the refractory inorganic oxide support, dried and fired to leave only the noble metal. It is done. When the organic acid is contained in the noble metal aqueous solution at the molar ratio, the loading of the noble metal can be controlled so that the area ratio of DS and DL is 1/4 to 4/1. If the molar ratio exceeds 2.0, heat generation during decomposition and combustion of the organic acid is large, the distribution of the noble metal particle diameter cannot be set within a predetermined range, and if it is less than 0.25, the effect of the organic acid is not sufficiently exhibited. Similarly, the noble metal particle size distribution may not be set within a predetermined range.
[0020]
The total supported amount of the catalyst component is preferably 10 to 350 g / L per liter of the refractory monolith support, and the supported amount of the HC adsorbent is 5 to 200 g / L. The supported amount of is preferably 1 to 200 g / L, and the supported amount of the noble metal is preferably 0.1 to 10 g / L.
[0021]
The monolithic structure type carrier is preferably a carrier structure made of a heat-resistant material. For example, a ceramic open flow or wall flow carrier structure, a SiC carrier, or a metal carrier can be used.
[0022]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.
[0023]
Example 1
Titanium oxide powder with an average particle size of 30 nm (anatase structure is 80% or more) is impregnated with an aqueous solution (total number of organic acids / number of platinum moles = 1.0) in which platinum dinitrodiamminate and citric acid are dissolved. , Dried at 150 ° C. for 24 hours, then calcined at 300 ° C. for 1 hour and then at 600 ° C. for 1 hour to obtain Pt-supported titanium oxide powder (powder a). The Pt concentration of this powder a was 15.0%.
267 g of the above-mentioned Pt-supported titanium oxide powder (powder a), 1000 g of β-zeolite powder, 483 g of activated alumina powder, 50 g of nitric acid acidic alumina sol (a sol obtained by adding 10% nitric acid to 10% boehmite alumina) and pure water 2000 g was put into a magnetic ball mill, mixed and pulverized to obtain a slurry liquid. This slurry liquid is attached to a cordierite monolith carrier (400 cell / 8 mil, 1.3 L), excess slurry in the cell is removed by air flow, dried, and baked at 400 ° C. for 1 hour. The coating operation was repeated until the weight reached 180 g / L to obtain Catalyst-a of this example.
[0024]
(Example 2)
Titanium oxide powder with an average particle size of 30 nm (anatase structure is 80% or more) is impregnated with an aqueous solution (total number of organic acids / number of platinum moles = 1.0) in which platinum dinitrodiamminate and citric acid are dissolved. , Dried at 150 ° C. for 24 hours, then calcined at 300 ° C. for 1 hour and then at 600 ° C. for 1 hour to obtain a Pt-supported titanium oxide powder (powder b). The Pt concentration of this powder b was 5.0%.
800 g of the above-mentioned Pt-supported titanium oxide powder (powder b), 980 g of β-zeolite powder, 20 g of nitric acid acidic alumina sol (a sol obtained by adding 10% nitric acid to 10% boehmite alumina) and 2000 g of pure water in a magnetic ball mill The slurry was added and mixed and ground to obtain a slurry. This slurry liquid is attached to a cordierite monolith carrier (400 cell / 8 mil, 1.3 L), excess slurry in the cell is removed by air flow, dried, and baked at 400 ° C. for 1 hour. The coating operation was repeated until the weight reached 180 g / L to obtain catalyst-b of this example.
[0025]
(Example 3)
Except that the total number of moles of organic acid / the number of moles of platinum = 1.5, the same operation as in Example 1 was repeated to obtain catalyst-c of this example.
[0026]
Example 4
Except that the total number of moles of organic acid / the number of moles of platinum was 2.0, the same operation as in Example 1 was repeated to obtain catalyst-d of this example.
[0027]
(Example 5)
Except that the total number of moles of organic acid / the number of moles of platinum = 0.5, the same operation as in Example 1 was repeated to obtain catalyst-e of this example.
[0028]
(Example 6)
An aqueous solution (organic acid) in which W 0.1 Zr 0.9 O 2 powder is used instead of titanium oxide powder having an average particle size of 30 nm (anatase structure is 80% or more) and platinum dinitrodiamminate and citric acid are dissolved. And then dried at 150 ° C. for 24 hours, calcined at 300 ° C. for 1 hour and then at 600 ° C. for 1 hour to obtain a Pt-supported zirconium oxide powder (powder c) ) The Pt concentration of this powder c was 15.0%.
267 g of Pt-supported zirconium oxide powder (powder c), 1000 g of β-zeolite powder, 483 g of activated alumina powder, 50 g of nitric acid acidic alumina sol (a sol obtained by adding 10% nitric acid to 10% boehmite alumina) and pure water 2000 g was put into a magnetic ball mill, mixed and pulverized to obtain a slurry liquid. This slurry liquid is attached to a cordierite monolith carrier (400 cell / 8 mil, 1.3 L), excess slurry in the cell is removed by air flow, dried, and baked at 400 ° C. for 1 hour. The coating operation was repeated until the weight reached 180 g / L to obtain Catalyst-f of this example.
[0029]
(Example 7)
Except that S 0.1 Zr 0.9 O 2 powder was used instead of W 0.1 Zr 0.9 O 2 powder, the same operation as in Example 6 was repeated to obtain catalyst-g of this example. Obtained.
[0030]
(Example 8)
The same operation as in Example 1 was repeated except that 700 g of β-zeolite powder and 300 g of ZSM5 powder were used instead of 1000 g of β-zeolite powder to obtain catalyst-h of this example.
[0031]
Example 9
Except for using β-zeolite powder 1000 g, β-zeolite powder 400 g, mordenite powder 200 g, ZSM5 powder 200 g, and USY powder 200 g were used in the same manner as in Example 1 to obtain catalyst-i of this example. It was.
[0032]
(Example 10)
A catalyst-j of this example was obtained in the same manner as in Example 1 except that 134 g of powder a and 134 g of Pt 15.0% supported ZrO 2 were used instead of powder a267 g.
[0033]
(Example 11)
The same procedure as in Example 1 was carried out except that powder a134 g and Pt 15.0% supported W 0.1 Zr 0.9 O 2 powder 134 g were used instead of powder a267 g to obtain catalyst-k of this example. It was.
[0034]
(Example 12)
Obtained in place of the powder A267g, except for using a powder a134g and Pt15.0% supported S 0.1 Zr 0.9 O 2 powder 134g performs the same operation as in Example 1, the catalyst -l of this example It was.
[0035]
(Example 13)
A catalyst-m of this example was obtained in the same manner as in Example 1 except that 220 g of powder a and 700 g of Pt 1.0% supported β-zeolite powder were used instead of powder a.
[0036]
(Example 14)
A catalyst-n of this example was obtained in the same manner as in Example 1 except that 700 g of β-zeolite powder was used instead of 1000 g of β-zeolite powder.
[0037]
(Example 15)
A catalyst-o of this example was obtained in the same manner as in Example 1 except that 1500 g of β-zeolite powder was used instead of 1000 g of β-zeolite powder.
[0038]
(Example 16)
Except that acetic acid was used instead of citric acid, the same operation as in Example 1 was performed to obtain catalyst-p of this example.
[0039]
(Example 17)
Except that succinic acid was used instead of citric acid, the same operation as in Example 1 was performed to obtain catalyst-q of this example.
[0040]
(Example 18)
Except for using titanium oxide having an average particle diameter of 100 nm, the same operation as in Example 1 was performed to obtain catalyst-r of this example.
[0041]
(Comparative Example 1)
Except for not using β-zeolite, the same operation as in Example 1 was performed to obtain catalyst-aa of this example.
[0042]
(Comparative Example 2)
Except for using 267 g of Pt 15% -supported β-zeolite in place of the powder a267 g, the same operation as in Example 1 was performed to obtain catalyst-bb of this example.
[0043]
(Comparative Example 3)
Except not using organic acid, operation similar to Example 1 was performed and the catalyst-cc of this example was obtained.
[0044]
(Comparative Example 4)
Except that the total number of moles of organic acid / the number of moles of platinum = 10, the same operation as in Example 1 was performed to obtain catalyst-dd of this example.
[0045]
(Comparative Example 5)
Except for using titanium oxide having an average particle size of 100 nm and a rutile structure, the same operation as in Example 1 was performed to obtain catalyst-ee of this example.
[0046]
Table 1 shows the specifications of the exhaust gas purifying catalysts of the above Examples and Comparative Examples.
[0047]
[Table 1]
About each said Example and comparative example, the purification characteristic evaluation (ECE + EUDC of Europe) of HC and CO was performed on the following evaluation conditions using the evaluation system of FIG.
[0049]
<Durability conditions>
Engine displacement 2500cc
Fuel JIS No. 2 gas oil catalyst inlet gas temperature 600 ℃
Endurance time 100 hours [0050]
<Performance evaluation conditions>
Catalyst capacity Catalyst 1.3L
Evaluation vehicle Nissan Motor Co., Ltd. V type 6 cylinder 2.5L diesel engine
Moreover, about the purification rate of HC and CO, following formula (3) and (4)
HC purification rate (%)
= ([Catalyst inlet HC concentration] − [Catalyst outlet HC concentration]) / [Catalyst inlet HC concentration] × 100 (3)
CO purification rate (%)
= ([Catalyst inlet CO concentration]-[catalyst outlet CO concentration]) / [catalyst inlet CO concentration] × 100 (4)
The results are shown in Table 2.
[0052]
[Table 2]
Each of the above examples has higher catalytic activity than the above comparative examples, and is excellent in purification performance of unburned HC, CO and SOF from low temperatures. As a diesel engine exhaust gas purification catalyst, HC, CO and It was confirmed that SOF can be purified with high efficiency.
[0054]
【The invention's effect】
In the catalyst of the present invention, since noble metal particles having different particle diameters are mixed on a specific heat-resistant inorganic oxide support, HC, CO and SOF in exhaust gas of an internal combustion engine including diesel engine exhaust gas are used. The catalyst which can purify | clean efficiently can be provided.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing an evaluation system for an exhaust gas purifying catalyst.
[Explanation of symbols]
1 Engine 2 Catalyst
Claims (5)
上記触媒成分が、ＨＣ吸着材と、耐熱性無機酸化物担体に担持された貴金属とを含有し、
上記耐熱性無機酸化物担体が、次式（１）及び（２）で表されるジルコニウム酸化物、並びにアナターゼ型構造を含む１００ｎｍ以下の粒径を有するチタニウム酸化物から成る群から選ばれる少なくとも１種の酸化物を含有して成り、
上記貴金属は、貴金属塩の水溶液にクエン酸、酢酸及び蓚酸から成る群より選ばれた少なくとも１種の有機酸を含有させ、貴金属と有機酸のモル比（有機酸の総モル数／貴金属のモル数）を０．２５〜２．０として耐熱性無機酸化物担体に担持されていると共に、粒径の異なる貴金属粒子が混在していることを特徴とする排気ガス浄化用触媒。
ＷＸＺｒ１−ＸＯ２ ・・・ （１）
（式中のＷはタングステン、Ｘは０．０５〜０．２５を示す）
ＳＸＺｒ１−ＸＯ２ ・・・ （２）
（式中のＳは硫黄、Ｘは０．０５〜０．２５を示す）An exhaust gas purifying catalyst comprising a monolithic support coated with a catalyst component,
The catalyst component contains an HC adsorbent and a noble metal supported on a heat-resistant inorganic oxide carrier,
The heat-resistant inorganic oxide support is at least one selected from the group consisting of zirconium oxides represented by the following formulas (1) and (2) and titanium oxide having a particle size of 100 nm or less including an anatase type structure. Containing seed oxides,
The noble metal contains at least one organic acid selected from the group consisting of citric acid, acetic acid and oxalic acid in an aqueous solution of a noble metal salt, and a molar ratio of the noble metal to the organic acid (total number of organic acids / mol of noble metal). The exhaust gas purifying catalyst is characterized in that it is supported on a heat-resistant inorganic oxide carrier with a number) of 0.25 to 2.0 and precious metal particles having different particle sizes are mixed.
W X Zr 1-X O 2 (1)
(W in the formula represents tungsten, and X represents 0.05 to 0.25)
S X Zr 1-X O 2 (2)
(In the formula, S represents sulfur and X represents 0.05 to 0.25)
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| JP5237616B2 (en) * | 2007-11-27 | 2013-07-17 | 石福金属興業株式会社 | Method for producing a titanium oxide carrier comprising a platinum group metal or an alloy of a platinum group metal and another metal supported thereon |
| JP6087362B2 (en) * | 2012-09-26 | 2017-03-01 | エヌ・イーケムキャット株式会社 | Platinum-based oxidation catalyst and exhaust gas purification method using the same |
| CA2892683A1 (en) | 2012-12-12 | 2014-06-19 | Basf Corporation | Catalyst compositions, catalytic articles, systems and processes using large particle molecular sieves |
| US8980209B2 (en) | 2012-12-12 | 2015-03-17 | Basf Corporation | Catalyst compositions, catalytic articles, systems and processes using protected molecular sieves |
| JP6511304B2 (en) * | 2015-03-16 | 2019-05-15 | 株式会社Ｓｏｋｅｎ | Particulate matter detection sensor |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02180639A (en) * | 1989-01-06 | 1990-07-13 | N E Chemcat Corp | Exhaust gas purifying catalyst for reducing generation of hydrogen sulfide and its manufacture |
| JPH05293380A (en) * | 1992-04-15 | 1993-11-09 | Toyota Central Res & Dev Lab Inc | Catalyst for purification of exhaust gas, production of this catalyst, and purifying method of exhaust gas |
| JPH09103679A (en) * | 1995-10-11 | 1997-04-22 | Toyota Motor Corp | Exhaust gas-purifying catalyst for diesel engine |
| JPH1033985A (en) * | 1996-07-19 | 1998-02-10 | Ict:Kk | Catalyst for purifying exhaust gas from diesel engine |
| JP2001058131A (en) * | 1999-08-20 | 2001-03-06 | Toyota Central Res & Dev Lab Inc | Catalyst for exhaust gas treatment |
-
2000
- 2000-12-06 JP JP2000372119A patent/JP4600710B2/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02180639A (en) * | 1989-01-06 | 1990-07-13 | N E Chemcat Corp | Exhaust gas purifying catalyst for reducing generation of hydrogen sulfide and its manufacture |
| JPH05293380A (en) * | 1992-04-15 | 1993-11-09 | Toyota Central Res & Dev Lab Inc | Catalyst for purification of exhaust gas, production of this catalyst, and purifying method of exhaust gas |
| JPH09103679A (en) * | 1995-10-11 | 1997-04-22 | Toyota Motor Corp | Exhaust gas-purifying catalyst for diesel engine |
| JPH1033985A (en) * | 1996-07-19 | 1998-02-10 | Ict:Kk | Catalyst for purifying exhaust gas from diesel engine |
| JP2001058131A (en) * | 1999-08-20 | 2001-03-06 | Toyota Central Res & Dev Lab Inc | Catalyst for exhaust gas treatment |
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