JP4106762B2 - Exhaust gas purification catalyst device and purification method - Google Patents
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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装置及び浄化方法に関し、特に自動車等の内燃機関から排出される排気ガス中の有害成分である炭化水素（以下、「ＨＣ」と称す）、一酸化炭素（以下、「ＣＯ」と称す）及び窒素酸化物（以下、「ＮＯｘ」と称す）を同時に除去する三元触媒であって、特に難燃なＨＣを高効率で浄化する排気ガス浄化用触媒装置及び浄化方法に関する。
【０００２】
【従来の技術】
従来より、排気ガス浄化用触媒は高効率でＨＣを浄化するために多段配置された場合、未燃排ガス中には難燃ＨＣ（例えば飽和炭化水素：パラフィン）が増加するため、排気下流の触媒は上流触媒に比べて効率が悪化する。その為、難燃ＨＣ浄化能に優れた排気ガス浄化用触媒及び浄化方法の開発が期待されている。
【０００３】
係る排気ガス浄化用触媒としては、例えば、特開昭６１−２３４９３５号公報、特開昭６２−２８２６４１号公報、特開平５−２００２８７号公報に開示されているものがある。
【０００４】
特開昭６１−２３４９３５号公報に記載された排気ガス浄化用触媒は、白金、ロジウム及びジルコニウムから成る組成物をガラス繊維担体に担持させたものであり、具体的にはシリカ等のガラス繊維担体にジルコニアウォッシュコートを担持し、更にロジウム、白金、及びパラジウムなどの白金族元素を含浸させた構造のものである。
【０００５】
また、特開昭６２−２８２６４１号公報には、ロジウムを酸化ジルコニウムに担持させた排気ガス浄化用触媒が開示されており、具体的にはロジウムを含有させた酸化ジルコニウム、活性アルミナ、酸化セリウムとアルミナゾルとを含むスラリーを、担体に付着・乾燥・焼成した後、白金を担持させたものである。
【０００６】
特開平５−４９９２９号公報には、活性アルミナからなる触媒担持層をもつ一体型構造体の排ガスが流入する入口側にパラジウム及びロジウムが担持され、排ガスが流出する出口側に白金及びロジウムが担持された触媒で、ロジウムの担持量が入口側より出口側に多いことを特徴とする排気ガス浄化用触媒が開示されている。
【０００７】
【発明が解決しようとする課題】
しかし、前記公報中に記載された従来の触媒及び浄化方法では、触媒容量を増加させ、より一層排気成分残存率を低下させようとした場合、排気ガス下流の触媒による浄化が進み、転化しにくいＨＣ成分割合が増加するため、排ガス雰囲気をＨＣ燃焼に適した酸化雰囲気にしても、浄化性能が悪化するという問題点があった。
【０００８】
従って、本発明の目的は、従来の排気ガス浄化用触媒及び触媒装置よりも、ＨＣ浄化性能が向上し、特に、今まで未浄化だったＨＣ成分に対して、高い浄化性能を有する排気ガス浄化用触媒装置及びその浄化方法を提供することに有る。
【０００９】
本発明者らは、上記課題を解決するために研究した結果、未浄化ＨＣの主成分であるパラフィン系の炭化水素の触媒活性を向上させるために、触媒成分担持層中にＰｔとＺｒＯ2 を含有させ、ＺｒＯ2 上にのみＰｔを存在させると共に、更に好適には、前記Ｐｔ担持ＺｒＯ2 触媒をより有効に機能させるため、Ｐｔ表面上のＨＣ吸着被毒（主に芳香族系炭化水素による）を制御するために当該Ｐｔ担持ＺｒＯ2 触媒の上流に芳香族炭化水素を吸着する触媒を配置した上で、最適な雰囲気に制御することにより、従来未浄化であったＨＣ成分の浄化性能が著しく向上・維持されることを見出し、本発明を完成した。
【００１０】
すなわち、本発明（第１発明）の排気ガス浄化用触媒装置は、触媒を複数配置した排気ガス浄化用触媒装置であって、
最下流に配置された触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ2 ）とを含み、かつ触媒成分であるＰｔがＺｒＯ2にのみ担持されている一体構造型触媒であり、
排気ガス浄化用触媒装置入口での排気ガス雰囲気を制御する手段と、前記最下流の触媒Ｂの入口手前で空気又は酸素を断続的に導入して前記最下流の触媒Ｂの入口の排気ガス雰囲気を制御する手段とを配置してなることを特徴とする。
【００１１】
これにより、特に排気浄化システム下流の未浄化ＨＣ成分中の特に安定で燃焼しにくいパラフィンを選択的に浄化する。これは、ＺｒＯ2 上のＰｔ表面状態が、パラフィン吸着に適した酸化状態に制御できるからである。
【００１２】
第１発明の好ましい態様として、第１発明の前記触媒Ｂのストイキからリーン雰囲気下におけるパラフィン成分に対する触媒活性を更に向上させるため、含有されるＰｔの量は、２ｇ／Ｌ〜１０ｇ／Ｌであり、ＺｒＯ2 へのＰｔ担持濃度は、１．０重量％〜５．０重量％である。また、Ｐｔを担持するＺｒＯ2 の初期表面積は、３０ｍ2 ／ｇ以上であることが好ましい。
これにより、ＺｒＯ2 上のＰｔ粒子状態が、パラフィン浄化に適した粒径分布にし、浄化性能をより高めることができる。
【００１３】
更に本発明（第２発明）の排気ガス浄化用触媒装置は、触媒を複数配置した排気ガス浄化用触媒装置であって、
最下流に配置された触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ2 ）とを含み、かつ触媒成分であるＰｔがＺｒＯ2にのみ担持されている一体構造型触媒であり、
更に排気ガス流れに対し最上流側に触媒成分としてＰｄ又は、ＰｄとＲｈを含む触媒Ａを配置し、
排気ガス浄化用触媒装置入口での排気ガス雰囲気を制御する手段と、前記最下流の触媒Ｂの入口手前で空気又は酸素を断続的に導入して前記最下流の触媒Ｂの入口の排気ガス雰囲気を制御する手段とを配置してなる。第２発明は、第１発明の触媒装置のパラフィン成分に対する高い触媒活性を更に維持・安定して発現させることを可能とする。
即ち、比較的燃えやすいＨＣの除去を予め行っておくことで、Ｐｔ担持ＺｒＯ2 触媒の難燃ＨＣ成分浄化率を更に向上することができる。
【００１４】
第２発明の好ましい態様として、触媒成分であるＰｄ又は、ＰｄとＲｈの含有量が、３ｇ／Ｌ〜１５ｇ／Ｌであることが好ましい。これは、未浄化成分を触媒Ｂの浄化性能に適した濃度とし、前記触媒装置のパラフィン成分に対する高い触媒活性をより有効に活用するためである。
【００１５】
更に、本発明（第３発明）の排気ガス浄化用触媒装置は、触媒を複数配置した排気ガス浄化用触媒装置であって、
最下流に配置された触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ2 ）とを含み、かつ触媒成分であるＰｔがＺｒＯ2にのみ担持されている一体構造型触媒であり、
更に排気ガス流れに対し最上流側に触媒成分としてＰｄ又は、ＰｄとＲｈを含む触媒Ａを配置し、
更に炭化水素吸着材と、Ｐｔ，Ｐｄ及びＲｈから成る群より選ばれる少なくとも一種以上の貴金属とを含む触媒Ｃを、前記最下流の触媒Ｂと前記最上流の触媒Ａとの間に配置し、
排気ガス浄化用触媒装置入口での排気ガス雰囲気を制御する手段と、前記最下流の触媒Ｂの入口手前で空気又は酸素を断続的に導入して前記最下流の触媒Ｂの入口の排気ガス雰囲気を制御する手段とを配置してなることを特徴とする。
かかる第３発明は、触媒ＢのＰｔ表面上のＨＣ吸着被毒を更に有効に抑制することを可能とする。
【００１６】
第３発明の好まし態様として、含有される炭化水素吸着材が、ＭＦＩゼオライト、Ｙゼオライト、βゼオライト、モルデナイト及びフェリエライトから成る群より選ばれる少なくとも一種以上のゼオライトであり、その含有量は触媒容量１Ｌあたり５０ｇ／Ｌ〜３００ｇ／Ｌであることを特徴とする。
これは、触媒Ｂ中のＰｔ系触媒のＨＣ吸着被毒要因である主たるアロマ系ＨＣを更に効率良く吸着保持することができるからである。
その含有量が上記範囲内であると、経済的にも有効で、かつその効果が有効に機能できる。
【００１７】
また、第３発明の他の好ましい態様として、含有されるＰｔ，Ｐｄ及びＲｈから成る群より選ばれた少なくとも一種以上の貴金属の含有量が、触媒容量１Ｌあたり、１．０ｇ／Ｌ〜２０ｇ／Ｌであることを特徴とする。
これは、吸着保持したＨＣを充分浄化でき、触媒Ｂの触媒活性を更に有効に発揮させることができ、かつ経済的にも有効だからである。
【００１８】
更に、本発明（第４発明）は、排気ガス中の一酸化炭素、炭化水素および窒素酸化物を同時に浄化する排気ガス浄化方法であって、この方法は内燃機関から排出される排気ガスを、触媒を複数配置してなり、排気ガス流れに対して最下流の触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ 2 ）を含み、かつ触媒成分であるＰｔがＺｒＯ2 にのみ担持されている一体構造型触媒である排気ガス浄化用触媒装置と接触させ、
前記排気ガス浄化用触媒装置入口での排気ガス雰囲気を、酸素過剰率（Ｚ値）にして０．９＜Ｚ＜１．０の燃料過剰雰囲気に制御し、
かつ前記最下流の触媒Ｂの入口手前で空気又は酸素を断続的に導入し、前記最下流の触媒Ｂの入口の排気ガス雰囲気を、酸素過剰率（Ｚ値）にして１．０＜Ｚ＜１．５の範囲で制御することを特徴とする。これは、パラフィン浄化活性を安定して発現させるためである。
【００１９】
更に、本発明（第５発明）は、排気ガス中の一酸化炭素、炭化水素および窒素酸化物を同時に浄化する排気ガス浄化方法であって、
内燃機関から排出される排気ガスを、触媒を複数配置してなり、排気ガス流れに対して最下流の触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ2 ）を含み、活性種であるＰｔがＺｒＯ2 にのみ担持されている一体構造型触媒であり、更に排気ガス流れに対して最上流側に触媒成分としてＰｄ又は、ＰｄとＲｈを含む触媒Ａを配置してなる排気ガス浄化用触媒装置と接触させ、
前記排気ガス浄化用触媒装置入口での排気ガス雰囲気を、酸素過剰率（Ｚ値）にして０．９＜Ｚ＜１．０の燃料過剰雰囲気に制御し、
かつ前記最下流の触媒Ｂの入口手前で空気又は酸素を断続的に導入し、前記下流側触媒入口の排気ガス雰囲気を、酸素過剰率（Ｚ値）にして１．０＜Ｚ＜１．５の範囲で制御することを特徴とする。
【００２０】
第２発明の触媒装置において、排気ガス浄化用触媒装置入口での排気ガス雰囲気を酸素過剰率（Ｚ値）を、０．９を超えて１．０未満の燃料過剰雰囲気に制御する。これは、最上流側に配置する触媒Ａの活性主成分をＰｄとすることで、僅かに燃料過剰雰囲気とした時の活性が高くできるため、ＨＣ浄化特性をコントロールでき、最下流の触媒Ｂ入口雰囲気のＨＣ成分を、最下流の優れたＨＣ浄化活性を有するＰｔ担持ＺｒＯ2 触媒Ｂの対象とすることができる。
【００２１】
最下流の触媒Ｂ入口手前で空気又は酸素の如き酸素源を断続的に導入する。これは、最下流の触媒Ｂにおけるパラフィン浄化活性を、安定して発現させるためである。 即ち、定常的な酸素導入を行い雰囲気制御した場合、下流のＰｔ担持ＺｒＯ2触媒ＢのＰｔ表面状態が酸素被毒を受け、ＨＣ浄化率の低下を引き起こす。その対策として酸素源の断続的導入が必要となっている。
【００２２】
更に、第５発明において、最下流の触媒Ｂ入口の排気ガス雰囲気を、酸素過剰率（Ｚ値）にして１．０＜Ｚ＜１．５の範囲で制御する。
これは、最下流の触媒Ｂにおけるパラフィン浄化活性を安定して発現させるためである。前記排気ガス雰囲気を一定のＺ値に制御する方法としては、例えば前述の最下流の触媒Ｂ入口手前で空気又は酸素の如き酸素源を導入する方法が採用できる。
【００２３】
第１発明の排気ガス浄化用触媒装置に含有される触媒Ｂの触媒成分担持層に含有される貴金属としては、少なくとも白金（Ｐｔ）が含有される。
当該Ｐｔの含有量は、触媒１Ｌ容量中２〜１０ｇである。２ｇ未満では低温活性や浄化性能が十分に発現せず、逆に１０ｇを超えた場合、Ｐｔの触媒活性は飽和し、添加量に見合う性能向上は得られず経済性に乏しい。
【００２４】
前記Ｐｔが担持される基材としては、Ｐｔのパラフィン転化性能を向上させるため、ＺｒＯ2 が適切である。このＰｄを担持するＺｒＯ2 としては、バデレイ石型とジルコニア型のいずれも好ましく使用できる。特に、浄化性能を高めるために、上記酸化物（ＺｒＯ2 ）へのＰｔ担持濃度は、１．０〜５．０重量％の範囲が適切である。１．０重量％未満ではＰｔの熱耐久性が低下する。一方、５．０重量％を超えた場合、高濃度過ぎてＰｔ粒子が成長するため有効でない。
【００２５】
また、Ｐｔを担持するＺｒＯ2 の使用量は、触媒１Ｌあたり１０〜３００ｇである。１０ｇ未満だと充分な貴金属の耐久性が得られず、３００ｇより多く使用しても改良効果は飽和し有効でない。更に好ましくは、ＺｒＯ2 の初期表面積は１ｇあたり３０ｍ2 以上のものが適切である。これは担持されたＰｔが活性を発現するのに適切な粒径確保をするためで、１ｇあたり３０ｍ2 未満では、初期活性が低下し有効性が失われる。
【００２６】
第２発明の排気ガス浄化用触媒装置は、第１発明の排気ガス浄化用触媒装置中の排気ガス流れに対し最上流側に更に、触媒成分としてＰｄ又は、ＰｄとＲｈを含む排気ガス浄化用触媒Ａを配置したものである。これは、最下流の触媒Ｂが未浄化ＨＣの主成分である難燃ＨＣ（主としてパラフィン）を効率良く浄化するために、予め、先述成分以外のＨＣを浄化し、最下流の触媒Ｂ入口のガス濃度及び成分を最適にするものである。
【００２７】
更に、第２発明の排気ガス浄化用触媒装置におけるＰｄ又は、ＰｄとＲｈの含有量は、触媒１Ｌ容量中３〜２０ｇである。３ｇ未満では低温活性や浄化性能が十分に発現せず、逆に２０ｇを越えてもＰｄ又は、ＰｄとＲｈの触媒活性は飽和し、添加量に見合う性能向上は得られず経済性に乏しい。
【００２８】
第３発明の排気ガス浄化用触媒装置は、第１発明の排気ガス浄化用触媒装置中の最下流のＰｔ担持ＺｒＯ2 触媒Ｂの上流に又は第２発明の排気ガス浄化用触媒装置中の最下流のＰｔ担持ＺｒＯ2 触媒Ｂと、最上流のＰｄ又は、ＰｄとＲｈを含む触媒Ａとの間に、触媒成分として、炭化水素吸着材と、Ｐｔ，Ｐｄ及びＲｈから成る群より選ばれる少なくとも一種の貴金属とを含む排気ガス浄化用触媒Ｃを配置したものである。これは、第１発明又は第２発明の最下流触媒ＢのＰｔ系触媒のパラフィン系ＨＣ吸着の阻害を緩和して浄化能を更に効率良く引き出すために、阻害要因である他のＨＣを予め吸着し、除去する機能を付加するものである。
【００２９】
前記炭化水素吸着材としては、上記最下流触媒ＢのＰｔ系触媒のＨＣ吸着被毒要因である主にアロマ系ＨＣを更に効率良く吸着保持するため、ＭＦＩ型ゼオライト、Ｙゼオライト、βゼオライト、モルデナイト及びフェリエライトから成る群より選ばれる少なくとも１種が適切に用いられる。
当該炭化水素吸着材の含有量は触媒１Ｌ容量中５０〜３００ｇである。５０ｇ未満では、上記アロマ系ＨＣの吸着保持効果が充分に発現せず、逆に３００ｇを超えた場合、炭化水素吸着材の触媒活性は飽和し、添加量に見合う性能向上は得られず経済性に乏しい。
【００３０】
また、前記Ｐｔ，Ｐｄ及びＲｈから成る群より選ばれる少なくとも一種の貴金属の含有量は、触媒１Ｌ容量中１．０〜２０ｇである。このように貴金属を含有することで、吸着材に保持していた主にアロマ系ＨＣを浄化できるので、最下流のＰｔ系触媒Ｂの主にパラフィン系ＨＣ活性に悪影響を及ぼすことを防止する。
また、その含有量は、１．０ｇ未満では、吸着保持したＨＣを十分浄化できず、最下流触媒Ｂの活性を補助する機能が発揮できず、逆に２０ｇを超えた場合、当該効果は飽和し、添加量に見合う性能向上は得られず経済性に乏しい。
【００３１】
第４発明の排気ガス浄化方法では、上記したように、第１発明の排気ガス浄化用触媒装置の入口での排気ガス雰囲気を、酸素過剰率（Ｚ値）にして０．９＜Ｚ＜１．０の燃料過剰雰囲気に制御し、かつ最下流の触媒Ｂの入口の排気ガス雰囲気を、酸素過剰率にして１．０＜Ｚ＜１．５の範囲で制御するものである。これは、最下流のＰｔ担持ＺｒＯ2 触媒Ｂが、この範囲内において最も高いレベルのパラフィン浄化性能を示すための制御である。
【００３２】
前記最下流の触媒Ｂの入口手前で空気等、例えば空気又は酸素等の酸素源を断続的に添加する。添加タイミングとしては、好ましくは１分間に３０回〜６０回の範囲である。これは第１発明の触媒装置によるパラフィン浄化活性を安定して発現させるためである。この方法において、断続的な酸素導入を行い排気ガス雰囲気を訂正範囲内のＺ値に制御するのは、最下流のＰｔ担持ＺｒＯ2 触媒ＢのＰｔ表面状態が酸素被毒を受けてＨＣ浄化率の低下を招くことを防止し、触媒装置におけるパラフィン浄化活性を安定して発現させるためである。尚、空気を用い、添加回数を３０〜６０回／分とした場合、添加量は１回当たり約１〜５ＬがＺ値を制御範囲内におさめる上で、好ましい。添加方法は例えばエアポンプによる添加が、正確な添加量を保つ上でより好ましい。
【００３３】
また、上記のように第５発明の排気ガス浄化方法では、第２発明の排気ガス浄化用触媒装置の触媒群の入口、即ち排気ガス浄化用触媒装置の入口の排気ガス雰囲気を、酸素過剰率（酸化成分濃度／還元成分濃度）にして０．９＜Ｚ＜１．０の若干還元成分過剰雰囲気に制御するものである。これにより、Ｐｄを触媒活性種の主成分とする最上流の触媒ＡのＨＣ浄化特性をコントロールし、最下流の触媒Ｂ入口雰囲気のＨＣ成分について最下流のＰｔ触媒Ｂが優れた活性を有するパラフィン系ＨＣにする効果を持たせることが可能となる。
【００３４】
また、第５発明の排気ガス浄化方法において、第２発明の排気ガス浄化用触媒装置の最下流の触媒Ｂ入口手前での排気ガス雰囲気を制御するために、空気又は酸素等の酸素源を断続的に添加する。添加タイミングとして好ましくは１分間に３０回〜６０回の範囲が適切である。３０回未満では、最下流触媒Ｂの活性に有利な雰囲気に維持することができず、６０回を越えて定常的に酸素を添加すると、逆にＰｔ表面を活性な状態に維持できないため効果的でない。尚、空気を用い、添加回数を３０〜６０回／分とした場合、添加量は１回当たり約１〜５ＬがＺ値を制御範囲内におさめる上で、好ましい。添加方法は例えばエアポンプによる添加が、正確な添加量を保つ上でより好ましい。
【００３５】
更に、第５発明の排気ガス浄化方法では、第２発明の排気ガス浄化用触媒装置の最下流の触媒Ｂ入口手前の排気ガス雰囲気を、酸素過剰率にして１．０＜Ｚ＜１．５の範囲で制御するものである。この範囲外の雰囲気では、上記第４発明の場合と同様の理由から、Ｐｔ表面を十分に活性な状態に維持できず、ＨＣ浄化率が低下するためである。
【００３６】
尚、本発明において酸素過剰率Ｚは、次の式で示される。
【数１】
前記のように第１発明、第２発明及び第３発明に用いる排気ガス浄化用触媒Ｂを製造するに際しては、まず、好ましくは３０ｍ2 ／ｇ以上の初期表面積を有するＺｒＯ2 にＰｔを含浸担持して、更に熱処理することにより、排気ガス浄化用触媒Ｂが得られる。排気ガス浄化用触媒Ｂにおいて、金属（Ｐｔ）の担体（ＺｒＯ2 ）への担持方法は特に限定されない。担持法としては金属成分を含む溶液に担体を浸して担持する含浸法、担体成分と金属成分の混合溶液に沈澱剤を加え、同時に両者の沈澱物を作り、これを焼成する共沈法、担体を金属成分に浸した後、攪拌しながら沈澱剤を加え、担体上に金属成分の沈澱を沈着させる沈着法、金属成分の沈澱をあらかじめ作った後、これと担体とをボールミルあるいは混和機で混練する混練法などが挙げられる。このように公知の担持方法の中から適宜選択して行うことができるが、特に含浸法を用いることが好ましい。
【００３８】
本発明の触媒装置を構成するＰｔの原料化合物としては、ジニトロジアンミン酸塩、硝酸塩および塩化物等の水溶性のものであれば任意のものが使用できる。
【００３９】
また、前記のように第２発明の排気ガス浄化用触媒装置においては、最上流の触媒Ａとして、Ｐｄを担持したアルミナと、Ｒｈを担持したアルミナを使用するのが好ましい。より好ましくは、Ｐｄを担持したアルミナとＰｄを担持したセリウム酸化物とを有効な範囲にＰｄを分配した形で使用される。
【００４０】
Ｐｄ、及びＲｈの原料化合物としては、ジニトロジアンミン酸塩、塩化物、硝酸塩等水溶性のものであれば任意のものが使用できる。
【００４１】
また、前記のように第３発明の排気ガス浄化用触媒装置においては、触媒Ｃの触媒成分として、まずジルコニウム酸化物（ジルコニア）、活性アルミナ、シリカ、チタニア、セリウム酸化物（セリア）等の担体に、Ｐｔ，Ｐｄ及びＲｈから成る群より選ばれる少なくとも１種の貴金属を担持したものを使用するのが好ましい。
【００４２】
貴金属の担体への担持方法は特に限定されない。担持法としては金属成分を含む溶液に担体を浸して担持する含浸法、担体成分と金属成分の混合溶液に沈殿剤を加え、同時に両者の沈殿物を作り、これを焼成する共沈法、担体を金属成分に浸した後、攪拌しながら沈殿剤を加え、担体上に金属成分の沈殿を沈着させる沈着法、金属成分の沈殿をあらかじめ作った後、これと担体とをボールミルあるいは混和機で混練する混練法などが挙げられる。このように公知の担持方法の中から適宜選択して行うことができるが、特に含浸法を用いることが好ましい。
【００４３】
本発明の触媒を構成する貴金属の原料化合物としては、ジニトロジアンミン酸塩、硝酸塩および塩化物等の水溶性のものであれば任意のものが使用できる。
【００４４】
更に、第１発明、第２発明及び第３発明排気ガス浄化用触媒装置中の貴金属触媒成分に加えて、担体との密着性を高める為に、活性アルミナ、ベーマイトアルミナ、アルミナゾルからなる群より選ばれた１種を加えることが好ましい。また第３発明の排気ガス浄化溶触媒装置中の炭化水素吸着材に加えて、担体との密着性を高める為に、シリカを加えることが好ましい。
【００４５】
このようにして得られる本発明にかかる排気ガス浄化用触媒は、無担体でも有効に使用することができるが、粉砕・スラリーとし、触媒担体にコートして、４００〜９００℃で焼成して用いることが好ましい。触媒担体としては、公知の触媒担体の中から適宜選択して使用することができ、例えば耐火性材料からなるモノリス担体やメタル担体等が挙げられる。
【００４６】
従って、得られた前記Ｐｔ担持ＺｒＯ2 粉末に、所望により活性アルミナ、ベーマイトアルミナおよびアルミナゾルからなる群より選ばれた１種を加えて湿式にて粉砕してスラリーとし、触媒担体に付着させ、４００〜６５０℃の範囲の温度で空気中及び／又は空気流通下で焼成を行うことで、第１発明、第２発明及び第３発明で用いる排気ガス浄化用触媒Ｂを得ることができる。
【００４７】
更に、得られた前記Ｐｄ担持アルミナ粉末、Ｐｄ担持セリウム酸化物粉末、Ｒｈ担持アルミナ粉末からなる群より選ばれた一種に所望により、活性アルミナ、ベーマイトアルミナ、アルミナゾルからなる群より選ばれた１種を加えて湿式に粉砕してスラリーとし、触媒担体に付着させ、４００〜６５０℃の範囲の温度で空気中及び／又は空気流通下で焼成を行うことで、第２発明で用いる排気ガス浄化用触媒Ａを得ることができる。
【００４８】
更に、ロジウム、及びパラジウムの相乗作用を効率よく発現させるために、パラジウムを含有する触媒成分層はコート層の下側（内層側）に配置し、ロジウムを含有する触媒成分層はコート層の上側（表層側）に配置することが好ましい。このように、触媒成分をコート層の下側とコート層の上側に配置する方法として、例えば次の方法、逐次コーティング法、逐次含浸法等が用いられる。
【００４９】
更に、炭化水素吸着材に、シリカを加えて湿式粉砕してスラリーとし、このスラリーを触媒担体に付着させ、更に、得られた前記Ｐｔ，Ｐｄ及びＲｈから成る群より選ばれる少なくとも一種の貴金属担持ジルコニア酸化物（ジルコニア）、活性アルミナ、シリカ、チタニア、セリウム酸化物（セリア）等の粉末に、活性アルミナ、ベーマイトアルミナ、アルミナゾルから成る群より選ばれた１種を加えて湿式に粉砕してスラリーとし、このスラリーを前記炭化水素吸着材が既に付着された触媒担体に付着させ、４００〜６５０℃の範囲の温度で空気中及び／又は空気流通下で焼成を行うことで、第３発明で用いる排気ガス浄化用触媒Ｃを得ることができる。
【００５０】
また、触媒の浄化効率を良くするために、炭化水素吸着材を含有する触媒成分層はコート層の下側（内層側）に配置し、貴金属を含有する触媒成分層はコート層上側（表層側）に配置することが好ましい。このように、触媒成分をコート層の下側とコート層の上側に配置する方法として、例えば次の方法、逐次コーティング法、逐次含浸法等が用いられる。
【００５１】
前記触媒担体の形状は、特に制限されないが、通常はハニカム形状で使用することが好ましく、ハニカム状の各種基材に触媒粉末を塗布して用いられる。
このハニカム材料としては、一般にセラミック等のコージェライト質のものが多く用いられるが、フェライト系ステンレス等の金属材料からなるハニカム材料を用いることも可能であり、更には触媒成分粉末そのものをハニカム状に成形しても良い。触媒の形状をハニカム状とすることにより、触媒と排気ガスとの接触面積が大きくなり、圧力損失も抑制できるため自動車用排気ガス浄化用触媒として用いる場合に極めて有効である。
【００５２】
ハニカム材料に付着させる触媒成分コート層の量は、触媒成分全体のトータルで、触媒１Ｌあたり、５０ｇ〜４００ｇが好ましい。
触媒成分担持層が多い程、触媒活性や触媒寿命の面からは好ましいが、コート層が厚くなりすぎると、触媒成分担持層内部で反応ガスが拡散不良となり触媒と十分に接触できなくなるため、活性に対する増量効果が飽和し、更にはガスの通過抵抗も大きくなってしまう。このため、コート層量は、上記触媒１Ｌあたり５０ｇ〜４００ｇが好ましい。
【００５３】
第２発明の触媒装置において、触媒装置入口での排気ガス雰囲気を酸素過剰率（Ｚ値）を、０．９〜１．０未満の燃料過剰雰囲気に制御する。これは、上流側に配置する触媒の活性主成分をＰｄとすることで、僅かに燃料過剰雰囲気とした時の活性が高くできるため、ＨＣ浄化特性をコントロールでき、最下流の触媒Ｂ入口雰囲気のＨＣ成分を、最下流の優れたＨＣ浄化活性を有するＰｔ担持ＺｒＯ2 触媒Ｂの対象とすることができる。
【００５４】
本発明を次の実施例及び比較例により更に具体的に説明するが、本発明の趣旨に反しない限り、本発明はこれらの実施例に限定されるものではない。
【００５５】
実施例１
γ−アルミナ粉末に硝酸パラジウム水溶液を含浸し、１５０℃で１２時間乾燥した後、４００℃で１時間焼成して、Ｐｄ担持アルミナ粉末（粉末Ａ）を得た。この粉末ＡのＰｄ濃度は１．７重量％であった。
【００５６】
ランタン１モル％（Ｌａ2 Ｏ3 に換算して２重量％）とジルコニウム３２モル％（ＺｒＯ2 に換算して２５重量％）を含むセリウム酸化物粉末に硝酸パラジウム水溶液を含浸し、１５０℃で１２時間乾燥した後、４００℃で１時間焼成して、Ｐｄ担持セリウム酸化物（Ｌａ０．０１Ｚｒ０．３２Ｃｅ０．６７Ｏｘ）粉末（粉末Ｂ）を得た。この粉末ＢのＰｄ濃度は０．７５重量％であった。
【００５７】
上記粉末Ａ１４６ｇ、粉末Ｂ１００ｇと、硝酸水溶液２５４ｇを磁性ボールミルに投入し、混合・粉砕してスラリーを得た。このスラリー液をコージェライト質モノリス担体（１．７Ｌ、４００セル／平方インチ）に付着させ、空気流にてセル内の余剰のスラリーを除去・乾燥し、５００℃で１時間焼成した。この作業を２度行い、コート量重量２００ｇ／Ｌ−担体の触媒Ａを得た。パラジウム担持量は３．５３ｇ／Ｌ（１００ｇ／ｃｆ）であった。
【００５８】
ＺｒＯ2 粉末にジニトロジアンミン白金水溶液を含浸し、１５０℃で１２時間乾燥した後、４００℃で１時間焼成して、Ｐｔ担持ＺｒＯ2 粉末（粉末Ｃ）を得た。この粉末ＣのＰｔ濃度は１．５重量％であった。
【００５９】
上記粉末Ｃ１９５ｇとベーマイトアルミナ５ｇと硝酸水溶液２９５ｇを磁性ボールミルに投入し、混合・粉砕してスラリーを得た。このスラリー液をコージェライト質モノリス担体（１．７Ｌ、４００セル／平方インチ）に付着させ、空気流にてセル内の余剰のスラリーを除去・乾燥し、４００℃で１時間焼成した。コート層重量２２５ｇ／Ｌ−担体の触媒Ｂを得た。Ｐｔの担持量は２．８３ｇ／Ｌ（８０ｇ／ｃｆ）であった。
【００６０】
上記触媒Ａ（上流側触媒）を排気上流に、上記触媒Ｂ（下流側触媒）を排気下流に配置し、触媒Ａの入口を酸素過剰率Ｚ＝０．９２とし、更に触媒Ｂの入口において２次空気を断続的に加え、Ｚ＝１．２となるように制御した。
【００６１】
実施例２
実施例１で得られた触媒Ａにおいて更にＲｈを添加し、Ｐｄ／Ｒｈ触媒（Ｐｄ／Ｒｈ＝５．３ｇ／Ｌ）を用いた以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００６２】
実施例３
実施例１で得られた触媒ＢにおいてＰｔ担持ＺｒＯ2 粉末のＰｔ濃度を１．５重量％から４．８重量％として用いた以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００６３】
実施例４
実施例１で得られた上流触媒Ａの入口の排気ガス雰囲気をＺ＝０．９８とし、実施例１で得られた下流触媒Ｂの入口をＺ＝１．４とした以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００６４】
実施例５
排気上流側に配置した実施例１で得られた触媒ＡのＰｄ担持量を２．８３ｇ／Ｌとした以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００６５】
実施例６
排気下流側に配置した実施例１で得られた触媒ＢのＰｔ担持量を１．７７ｇ／Ｌに変更した以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００６６】
実施例７
排気下流側に配置した実施例１で得られた触媒ＢのＰｔ担持量はそのままでＰｔ担持濃度を０．５重量％に変更した以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００６７】
実施例８
排気下流側に配置した実施例１で得られた触媒ＢのＰｔ担持量はそのままでＰｔ担持濃度を６．０重量％に変更した以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００６８】
実施例９
ＺＳＭ−５ゼオライト粉末２８４ｇ、シリカゾル（固形分２０重量％）６００ｇ、水１０ｇを磁性ボールミルに投入し、混合・粉砕工程を経てスラリーを得た。このスラリー液をコージェライト質モノリス担体（０．７Ｌ、４００セル／平方インチ）に付着させ、空気流にてセル内の余剰のスラリーを除去・乾燥し、５００℃で１時間焼成した。この作業を数回繰り返し、トータルコート量重量１００ｇ／Ｌ−担体の触媒ａを得た。
【００６９】
更に、Ｐｄ担持アルミナ粉末（Ｐｄ担持濃度３．４重量％）とＰｄ担持セリウム酸化物粉末（Ｐｄ担持濃度１．５重量％）をそれぞれ１４６ｇ、１００ｇと、硝酸水溶液２５４ｇを磁性ボールミルに投入し、混合・粉砕してスラリーを得た。このスラリー液を触媒ａに付着させ、空気流にてセル内の余剰のスラリーを除去・乾燥し、５００℃で１時間焼成した。この作業を２度行い、Ｐｄ担持層のコート量重量１００ｇ／Ｌ−担体の触媒Ｃを得た。パラジウム担持量は３．５３ｇ／Ｌ（１００ｇ／ｃｆ）であった。
【００７０】
図１に示すように、実施例１で得られた触媒Ａを排気ガス最上流に、実施例１で得られた触媒Ｂを排気最下流に、更に前記触媒Ｂの直前に触媒上記Ｃを配置し、触媒Ａの入口を酸素過剰率Ｚ＝０．９２とし、更に触媒Ｃの入口において２次空気を断続的に加え、Ｚ＝１．２となるように制御した。
【００７１】
実施例１０
実施例９で得られた触媒Ｃにおいて、ＨＣ吸着材としてＺＳＭ５ゼオライトの代わりにβゼオライト（Ｈ型、Ｓｉ／２Ａｌ＝７５）を用いた以外は、実施例９と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００７２】
実施例１１
実施例９で得られた触媒Ｃにおいて、ＨＣ吸着材としてＺＳＭ５ゼオライトに加えて、βゼオライト（Ｈ型、Ｓｉ／２Ａｌ＝７５）を更に１００ｇ／Ｌ加え、トータルのゼオライト量を２００ｇ／Ｌとして用いた以外は実施例９と同様にして排気ガス浄化溶触媒装置を構成し、制御した。
【００７３】
実施例１２
実施例９で得られた触媒Ｃにおいて、貴金属コート層のＰｄに加えて更にＲｈを添加した、Ｐｄ／Ｒｈ触媒層（Ｐｄ／Ｒｈ＝４．２４ｇ／Ｌ−５／１）を用いた以外は、実施例９と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００７４】
実施例１３
実施例９で得られた触媒Ｃにおいて、貴金属コート層のＰｄをＰｔに変更し、Ｐｔ／Ｒｈ触媒層（Ｐｔ／Ｒｈ＝４．２４ｇ／Ｌ−５／１）を用いた以外は、実施例１２と同様の排気ガス浄化用触媒装置を構成し、制御した。
【００７５】
実施例１４
実施例９で得られた触媒Ｃにおいて、ＨＣ吸着材としてＺＳＭ５ゼオライトの含有量を３０ｇ／Ｌに変更して用いた以外は、実施例９と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００７６】
実施例１５
実施例９で得られた触媒Ｃにおいて、貴金属コート層のＰｄ量を０．８ｇ／Ｌに変更して用いた以外は、実施例９と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００７７】
比較例１
排気下流に配置した実施例１で得られた触媒ＢをＰｄ触媒（Ｐｄ＝５．３ｇ／Ｌ、Ｐｄ担持ＺｒＯ 2 使用）とした以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００７８】
比較例２
排気下流に配置した実施例１で得られた触媒ＢのＰｔ担持材をＺｒＯ 2 からγ−アルミナに変更した以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００７９】
参考例１
排気上流に配置した実施例１で得られた触媒Ａ入口の排気ガス雰囲気をＺ＝０．８とした以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００８０】
参考例２
排気上流に配置した実施例１で得られた触媒Ａ入口の排気ガス雰囲気をＺ＝１．２とした以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００８１】
参考例３
排気下流に配置した実施例１で得られた触媒Ｂの入口雰囲気をＺ＝０．９５とした以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００８２】
参考例４
排気下流に配置した実施例１で得られた触媒Ｂの入口雰囲気をＺ＝１．６０とした以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００８３】
参考例５
排気下流に配置した実施例１で得られた触媒Ｂの入口雰囲気で２次空気を連続的に添加すること以外は、実施例１と同様にして排気ガス浄化用触媒装置を構成し、制御した。
【００８４】
参考例６
実施例１における触媒Ｂ中、Ｐｔ担持量を２．８３ｇ／Ｌ、Ｐｔ担持濃度を１．５重量％として、排気下流側に配置し排気ガス浄化用触媒装置を構成し、制御した。
【００８５】
試験例
前記実施例１〜１５及び比較例１ないし２、参考例１ないし６の排気ガス浄化用触媒装置（図１）について、下記評価条件で触媒活性評価を行った。
【００８６】
評価条件：車両評価（北米ＬＡ４モード、Ｂバック）
エンジン排気量 ２４００ｃｃ（直列４気筒）
ＩＷ ３２５０ ｌｂｓ
燃料 無鉛ガソリン
【００８７】
上記実施例１〜１５及び比較例１ないし２、参考例１ないし６で検討された排気ガス浄化用触媒装置の貴金属担持量（触媒１Ｌ中におけるパラジウム、ロジウム、白金の含有量）と制御方法及び触媒活性評価結果を排気ガス浄化用触媒装置により構成されたシステムトータルのＨＣ浄化性能として、その平均転化率（％）を表１にまとめて示す。
【００８８】
【表１】
【発明の効果】
以上説明したように、本発明の触媒装置は、ＨＣ浄化性能が向上し、特に従来未浄化であったＨＣ成分の浄化を著しく高める効果を奏する。
【００９０】
更に本発明の方法は、上流側触媒入口と下流側触媒入口の排気ガス雰囲気を、それぞれ適切な酸素過剰率に制御するように構成したものであるから、ＨＣ浄化性能が向上し、特に従来未浄化であったＨＣ成分の浄化を著しく向上させ、それを維持する効果を奏する。
【図面の簡単な説明】
【図１】本発明の排気ガス浄化用触媒装置の配置の一例を示す線図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification catalyst device and a purification method, and more particularly, hydrocarbons (hereinafter referred to as “HC”), carbon monoxide (hereinafter referred to as “HC”), which are harmful components in exhaust gas discharged from an internal combustion engine such as an automobile. , “CO”) and nitrogen oxide (hereinafter referred to as “NOx”), which simultaneously removes HC, which is particularly effective in purifying flame-retardant HC, and purification. Regarding the method.
[0002]
[Prior art]
Conventionally, when an exhaust gas purification catalyst is arranged in multiple stages to purify HC with high efficiency, flame-retardant HC (for example, saturated hydrocarbons: paraffin) increases in unburned exhaust gas. Is less efficient than the upstream catalyst. Therefore, development of an exhaust gas purification catalyst and a purification method excellent in flame retardant HC purification capability is expected.
[0003]
Examples of such an exhaust gas purifying catalyst include those disclosed in Japanese Patent Application Laid-Open No. 61-234935, Japanese Patent Application Laid-Open No. 62-282642, and Japanese Patent Application Laid-Open No. 5-200287.
[0004]
An exhaust gas purifying catalyst described in JP-A-61-234935 is obtained by supporting a composition comprising platinum, rhodium and zirconium on a glass fiber carrier, specifically, a glass fiber carrier such as silica. Is supported by a zirconia washcoat and impregnated with a platinum group element such as rhodium, platinum, or palladium.
[0005]
JP-A-62-282641 discloses an exhaust gas purifying catalyst in which rhodium is supported on zirconium oxide. Specifically, zirconium oxide containing rhodium, activated alumina, cerium oxide, and the like are disclosed. A slurry containing alumina sol is deposited on a carrier, dried and fired, and then supported with platinum.
[0006]
In Japanese Patent Laid-Open No. 5-49929, palladium and rhodium are supported on the inlet side into which exhaust gas flows, and platinum and rhodium are supported on the outlet side from which exhaust gas flows out, in an integral structure having a catalyst support layer made of activated alumina. An exhaust gas purifying catalyst characterized in that the supported amount of rhodium is larger on the outlet side than on the inlet side is disclosed.
[0007]
[Problems to be solved by the invention]
However, in the conventional catalyst and purification method described in the above publication, when an attempt is made to increase the catalyst capacity and further reduce the exhaust component residual rate, purification by the catalyst downstream of the exhaust gas proceeds and is difficult to convert. Since the HC component ratio increases, there is a problem that the purification performance deteriorates even if the exhaust gas atmosphere is changed to an oxidizing atmosphere suitable for HC combustion.
[0008]
Accordingly, an object of the present invention is to improve the HC purification performance over the conventional exhaust gas purification catalyst and catalyst device, and in particular, the exhaust gas purification having high purification performance for HC components that have not been purified so far. It is providing the catalyst apparatus for water and its purification method.
[0009]
As a result of researches to solve the above problems, the present inventors have found that in order to improve the catalytic activity of paraffinic hydrocarbons which are the main components of unpurified HC, Pt and ZrO are contained in the catalyst component-supporting layer.2Containing ZrO2More preferably, Pt is present only on the Pt-supported ZrO.2To make the catalyst function more effectively, the Pt-supported ZrO is used to control HC adsorption poisoning (mainly due to aromatic hydrocarbons) on the Pt surface.2It was found that the purification performance of HC components, which had not been purified in the past, can be significantly improved and maintained by controlling the optimal atmosphere after placing a catalyst that adsorbs aromatic hydrocarbons upstream of the catalyst. Completed the invention.
[0010]
That is, the exhaust gas purifying catalyst device of the present invention (first invention)Exhaust gas purification catalyst device with multiple catalystsBecause
Catalyst B arranged at the most downstream is the catalyst componentPt and zirconia (ZrO2 ) AndAnd catalyst componentsPt is ZrO2Only supported byIntegrated structure typeCatalystThe
Means for controlling the exhaust gas atmosphere at the inlet of the exhaust gas purifying catalyst device, and the exhaust gas atmosphere at the inlet of the most downstream catalyst B by intermittently introducing air or oxygen before the inlet of the most downstream catalyst B And means for controllingIt is characterized by that.
[0011]
This selectively purifies paraffin, which is particularly stable and difficult to burn, particularly in the unpurified HC component downstream of the exhaust purification system. This is ZrO2This is because the upper Pt surface state can be controlled to an oxidation state suitable for paraffin adsorption.
[0012]
As a preferred embodiment of the first invention, the first inventionCatalyst BIn order to further improve the catalytic activity for the paraffin component in a lean atmosphere from stoichiometric, the amount of Pt contained is 2 g / L to 10 g / L, and ZrO2 The Pt loading concentration on the surface is 1.0 wt% to 5.0 wt%. Also, ZrO carrying Pt2 The initial surface area of 30m2 / G or more is preferable.
As a result, ZrO2 The upper Pt particle state has a particle size distribution suitable for paraffin purification, and the purification performance can be further enhanced.
[0013]
Furthermore, the exhaust gas purifying catalyst device of the present invention (second invention)Exhaust gas purification catalyst device with multiple catalystsBecause
Catalyst B arranged on the most downstream side is Pt as a catalyst component.And zirconia (ZrO2 ) AndAnd catalyst componentsPt is ZrO2Only supported byIntegrated structure typecatalystAnd
Furthermore, on the most upstream side of the exhaust gas flowCatalyst containing Pd or Pd and Rh as catalyst componentPlace A,
Means for controlling the exhaust gas atmosphere at the inlet of the exhaust gas purifying catalyst device, and the exhaust gas atmosphere at the inlet of the most downstream catalyst B by intermittently introducing air or oxygen before the inlet of the most downstream catalyst B Means to controlArranged. The second invention makes it possible to maintain and stably develop a high catalytic activity for the paraffin component of the catalyst device of the first invention.
That is, by removing HC that is relatively flammable in advance, Pt-supported ZrO2 The flame retardant HC component purification rate of the catalyst can be further improved.
[0014]
As a preferred embodiment of the second invention,Catalyst componentThe content of Pd or Pd and Rh is preferably 3 g / L to 15 g / L. This is the unpurified componentCatalyst BThis is to make the concentration suitable for the purification performance of the catalyst, and to effectively utilize the high catalytic activity for the paraffin component of the catalyst device.
[0015]
Furthermore, the exhaust gas purifying catalyst device of the present invention (third invention)Exhaust gas purification catalyst device with multiple catalystsBecause
Catalyst B arranged on the most downstream side is Pt as a catalyst component.And zirconia (ZrO2 ) AndAnd catalyst componentsPt is ZrO2Only supported byIntegrated structure typecatalystAnd
Furthermore, the catalyst A containing Pd or Pd and Rh as a catalyst component is arranged on the most upstream side with respect to the exhaust gas flow,
Further, a catalyst C containing a hydrocarbon adsorbent and at least one or more noble metals selected from the group consisting of Pt, Pd and Rh is disposed between the most downstream catalyst B and the most upstream catalyst A,
Means for controlling the exhaust gas atmosphere at the inlet of the exhaust gas purifying catalyst device, and the exhaust gas atmosphere at the inlet of the most downstream catalyst B by intermittently introducing air or oxygen before the inlet of the most downstream catalyst B Means to controlIt is characterized by being arranged.
The third invention is a catalyst.BHC adsorption poisoning on the surface of Pt can be further effectively suppressed.
[0016]
As a preferred embodiment of the third invention, the hydrocarbon adsorbent contained is at least one zeolite selected from the group consisting of MFI zeolite, Y zeolite, β zeolite, mordenite and ferrierite, and the content thereof is a catalyst. The capacity is 50 g / L to 300 g / L per liter of capacity.
this is,Catalyst BThis is because the main aroma-based HC, which is an HC adsorption poisoning factor of the Pt-based catalyst, can be adsorbed and held more efficiently.
When the content is within the above range, it is economically effective and the effect can function effectively.
[0017]
As another preferred embodiment of the third invention, the content of at least one or more precious metals selected from the group consisting of Pt, Pd and Rh contained is 1.0 g / L to 20 g / L per catalyst capacity. It is characterized by being L.
This can sufficiently purify the adsorbed and retained HC,Of catalyst BThis is because the catalytic activity can be more effectively exhibited and is economically effective.
[0018]
Furthermore, the present invention (fourth invention) is an exhaust gas purification method for simultaneously purifying carbon monoxide, hydrocarbons and nitrogen oxides in exhaust gas, and this method comprises exhaust gas exhausted from an internal combustion engine,Multiple catalysts are arranged for exhaust gas flow.The most downstream catalystB is a catalyst component of Pt and zirconia (ZrO 2 ) And a catalyst componentPt is ZrO2 Only supported byIntegrated structure typecatalystIsContact with exhaust gas purification catalyst device,
The exhaust gas atmosphere at the exhaust gas purification catalyst inlet is controlled to an excess fuel atmosphere of 0.9 <Z <1.0 with an oxygen excess rate (Z value),
AndThe most downstream catalystBAir or just before the entranceoxygenIs introduced intermittently,Downstream catalyst BThe exhaust gas atmosphere at the inlet is controlled in the range of 1.0 <Z <1.5 with an oxygen excess rate (Z value). This is because the paraffin cleaning activity is stably expressed.
[0019]
Furthermore, the present invention (the fifth invention) is an exhaust gas purification method for simultaneously purifying carbon monoxide, hydrocarbons and nitrogen oxides in exhaust gas,
Exhaust gas discharged from the internal combustion engine,A plurality of catalysts are arranged, and the most downstream catalyst B with respect to the exhaust gas flowCatalyst componentAs PtAnd zirconia (ZrO2 ) And the active species Pt is ZrO2 Only supported byIntegrated structure typecatalystAndMoreOn the most upstream side of the exhaust gas flowCatalyst containing Pd or Pd and Rh as catalyst componentAArrangedContact with exhaust gas purification catalyst device,
The exhaust gas purification catalyst device inletThe exhaust gas atmosphere at is controlled to an excess fuel atmosphere of 0.9 <Z <1.0 with an oxygen excess rate (Z value),
And the most downstreamcatalystBAir or just before the entranceoxygenIs intermittently introduced, and the exhaust gas atmosphere at the downstream side catalyst inlet is controlled in the range of 1.0 <Z <1.5 in terms of oxygen excess (Z value).
[0020]
In the catalyst device of the second invention,Exhaust gas purification catalyst deviceThe exhaust gas atmosphere at the inlet is controlled so that the excess oxygen ratio (Z value) exceeds 0.9 and less than 1.0. this is,Most upstreamCatalyst placed on the sideABy using Pd as the main active component, the activity when slightly in excess of fuel can be increased, so that the HC purification characteristics can be controlled.Downstream catalyst BHC component of the inlet atmosphereMost downstreamPt-supported ZrO with excellent HC purification activity2 catalystBCan be the target of.
[0021]
Downstream catalyst BAn oxygen source such as air or oxygen is intermittently introduced before the entrance. this is,Downstream catalyst BThis is for stably expressing the paraffin purification activity in. That is, when the atmosphere is controlled by steady oxygen introduction, the downstream Pt-supported ZrO2catalystBThe Pt surface state of this receives oxygen poisoning and causes a reduction in the HC purification rate. As a countermeasure, intermittent introduction of an oxygen source is necessary.
[0022]
Furthermore, in the fifth invention,Downstream catalyst BThe exhaust gas atmosphere at the inlet is controlled in the range of 1.0 <Z <1.5 with an oxygen excess rate (Z value).
this is,Downstream catalyst BThis is to stably develop the paraffin purification activity in As a method for controlling the exhaust gas atmosphere to a constant Z value, for example,Downstream catalyst BA method of introducing an oxygen source such as air or oxygen before the entrance can be employed.
[0023]
Catalyst contained in the exhaust gas purifying catalyst device of the first inventionBAs the noble metal contained in the catalyst component supporting layer, at least platinum (Pt) is contained.
The content of Pt is 2 to 10 g in 1 L capacity of the catalyst. If it is less than 2 g, the low-temperature activity and the purification performance are not sufficiently exhibited. Conversely, if it exceeds 10 g, the catalytic activity of Pt is saturated, and the performance improvement corresponding to the amount added cannot be obtained, resulting in poor economic efficiency.
[0024]
The substrate on which Pt is supported is ZrO in order to improve the paraffin conversion performance of Pt.2Is appropriate. ZrO carrying this Pd2As for these, both the Badeley stone type and the zirconia type can be preferably used. In particular, in order to improve the purification performance, the oxide (ZrO2The concentration of Pt supported on) is suitably in the range of 1.0 to 5.0% by weight. If it is less than 1.0% by weight, the thermal durability of Pt is lowered. On the other hand, if it exceeds 5.0% by weight, it is not effective because Pt particles grow too high.
[0025]
Also, ZrO carrying Pt2Is used in an amount of 10 to 300 g per liter of the catalyst. If it is less than 10 g, sufficient durability of the noble metal cannot be obtained, and even if it is used in excess of 300 g, the improvement effect is saturated and is not effective. More preferably, ZrO2Initial surface area of 30m per gram2The above is appropriate. This is to secure an appropriate particle size for the supported Pt to express its activity.2Below, the initial activity is reduced and the effectiveness is lost.
[0026]
The exhaust gas purifying catalyst device of the second invention is the same as the exhaust gas purifying catalyst device of the first invention.Most upstream with respect to exhaust gas flowCatalyst for purifying exhaust gas further containing Pd or Pd and Rh as a catalyst component on the sideAIs arranged. this is,Downstream catalyst BIn order to efficiently purify flame retardant HC (mainly paraffin), which is the main component of unpurified HC, purify HC other than the aforementioned components in advance,Downstream catalyst BIt optimizes the gas concentration and composition at the inlet.
[0027]
Further, the content of Pd or Pd and Rh in the exhaust gas purifying catalyst device of the second invention is 3 to 20 g in 1 L capacity of the catalyst. If the amount is less than 3 g, the low-temperature activity and the purification performance are not sufficiently exhibited. Conversely, if the amount exceeds 20 g, the catalytic activity of Pd or Pd and Rh is saturated, and the performance improvement corresponding to the added amount cannot be obtained, resulting in poor economic efficiency.
[0028]
The exhaust gas purifying catalyst device of the third invention is the same as the exhaust gas purifying catalyst device of the first invention.Most downstreamPt-supported ZrO2 catalystBOr in the exhaust gas purifying catalyst device of the second invention.Most downstreamPt-supported ZrO2 catalystBWhen,Most upstreamCatalyst containing Pd or Pd and RhAThe catalyst for exhaust gas purification containing a hydrocarbon adsorbent and at least one noble metal selected from the group consisting of Pt, Pd and Rh as catalyst componentsCIs arranged. This is because of the first invention or the second inventionDownstream catalyst BIn order to alleviate the inhibition of paraffinic HC adsorption of the Pt-based catalyst and extract the purification ability more efficiently, a function of previously adsorbing and removing other HC as an inhibiting factor is added.
[0029]
As the hydrocarbon adsorbent, the most downstream catalystBIn order to more efficiently adsorb and retain mainly aroma-based HC, which is an HC adsorption poisoning factor of Pt-based catalysts, at least one selected from the group consisting of MFI type zeolite, Y zeolite, β zeolite, mordenite and ferrierite is Used appropriately.
The content of the hydrocarbon adsorbent is 50 to 300 g in 1 L capacity of the catalyst. When the amount is less than 50 g, the adsorption retention effect of the aroma-based HC is not sufficiently exhibited. Conversely, when the amount exceeds 300 g, the catalytic activity of the hydrocarbon adsorbent is saturated, and the performance improvement corresponding to the addition amount cannot be obtained. It is scarce.
[0030]
The content of at least one noble metal selected from the group consisting of Pt, Pd and Rh is 1.0 to 20 g in 1 L capacity of the catalyst. By containing noble metal in this way, it is possible to purify mainly aroma-based HC retained in the adsorbent, so the most downstreamofPt catalystBTo prevent adverse effects on paraffinic HC activity.
If the content is less than 1.0 g, the adsorbed and retained HC cannot be sufficiently purified, and the most downstream catalystBThe function of assisting the activity of the resin cannot be exhibited. Conversely, when the amount exceeds 20 g, the effect is saturated, the performance improvement corresponding to the amount added cannot be obtained, and the economy is poor.
[0031]
In the exhaust gas purification method of the fourth invention, as described above, the exhaust gas purification catalyst device of the first invention isThe exhaust gas atmosphere at the inlet is controlled to a fuel excess atmosphere of 0.9 <Z <1.0 with an oxygen excess rate (Z value), and the most downstream catalyst BThe exhaust gas atmosphere at the inlet is controlled in a range of 1.0 <Z <1.5 with an oxygen excess rate. this is,Most downstreamPt-supported ZrO2 catalystBHowever, this is the control for showing the highest level of paraffin purification performance within this range.
[0032]
SaidDownstream catalyst BAir, for example, air or oxygen before the entranceEtc.Oxygen source is added intermittently. The addition timing is preferably in the range of 30 to 60 times per minute. This is for stably expressing the paraffin purification activity by the catalyst device of the first invention. In this way,IntermittentTo control the exhaust gas atmosphere to a Z value within the correction range by introducing a proper oxygen,Most downstreamPt-supported ZrO2 catalystBThis is to prevent the Pt surface state from being poisoned by oxygen and causing a decrease in the HC purification rate, and to stably develop the paraffin purification activity in the catalyst device. When air is used and the number of additions is 30 to 60 times / minute, the addition amount is preferably about 1 to 5 L per time in order to keep the Z value within the control range. As an addition method, for example, addition by an air pump is more preferable for maintaining an accurate addition amount.
[0033]
Further, as described above, in the exhaust gas purification method of the fifth invention, the inlet of the catalyst group of the exhaust gas purification catalyst device of the second invention, that is,Exhaust gas purification catalyst deviceThe exhaust gas atmosphere at the inlet is controlled to an oxygen excess rate (oxidation component concentration / reduction component concentration) to a slightly reducing component excess atmosphere of 0.9 <Z <1.0. As a result, Pd is the main component of the catalytically active species.Most upstreamThe catalystAControl the HC purification characteristics ofDownstream catalyst BAbout HC component of entrance atmosphereMost downstreamPt catalystBIt is possible to have the effect of producing paraffinic HC having excellent activity.
[0034]
Further, in the exhaust gas purification method of the fifth invention, the exhaust gas purification catalyst device of the second invention is provided.Most downstreamcatalystBIn order to control the exhaust gas atmosphere in front of the inlet, an oxygen source such as air or oxygen is intermittently added. The addition timing is preferably in the range of 30 to 60 times per minute. Less than 30 timesMost downstreamcatalystBIt is not effective to maintain an atmosphere advantageous for the activity of oxygen, and if oxygen is constantly added over 60 times, the Pt surface cannot be maintained in an active state. When air is used and the number of additions is 30 to 60 times / minute, the addition amount is preferably about 1 to 5 L per time in order to keep the Z value within the control range. As an addition method, for example, addition by an air pump is more preferable for maintaining an accurate addition amount.
[0035]
Further, in the exhaust gas purification method of the fifth invention, the exhaust gas purification catalyst device of the second invention is provided.Most downstreamThe catalystBThe exhaust gas atmosphere before the entrance is controlled within the range of 1.0 <Z <1.5 with oxygen excess. This is because, in an atmosphere outside this range, the Pt surface cannot be maintained in a sufficiently active state for the same reason as in the case of the fourth invention, and the HC purification rate decreases.
[0036]
In the present invention, the oxygen excess ratio Z is represented by the following equation.
[Expression 1]
As described above, the exhaust gas purifying catalyst used in the first, second and third inventionsBIs preferably 30 m first.2 ZrO having an initial surface area of at least / g2 The catalyst for exhaust gas purification is impregnated with Pt and further heat-treated.BIs obtained. Exhaust gas purification catalystBMetal (Pt) support (ZrO2 The loading method is not particularly limited. As a supporting method, an impregnation method in which a support is immersed in a solution containing a metal component, a coprecipitation method in which a precipitant is added to a mixed solution of a support component and a metal component, and a precipitate is formed at the same time, and this is baked, a support After soaking in a metal component, a precipitant is added while stirring to deposit the metal component on the carrier. After the metal component has been deposited in advance, the carrier and the carrier are kneaded with a ball mill or a blender. And kneading method. Thus, it can be carried out by appropriately selecting from known supporting methods, but it is particularly preferable to use an impregnation method.
[0038]
As the Pt raw material compound constituting the catalyst device of the present invention, any water-soluble compound such as dinitrodiamminate, nitrate and chloride can be used.
[0039]
As described above, in the exhaust gas purifying catalyst device of the second invention,Most upstreamcatalystAIt is preferable to use alumina supporting Pd and alumina supporting Rh. More preferably, Pd is distributed in an effective range between alumina supporting Pd and cerium oxide supporting Pd.
[0040]
As the starting compound for Pd and Rh, any water-soluble compound such as dinitrodiamminate, chloride, nitrate can be used.
[0041]
Further, as described above, in the exhaust gas purifying catalyst device of the third invention, the catalystCFirst, at least one noble metal selected from the group consisting of Pt, Pd and Rh was supported on a carrier such as zirconium oxide (zirconia), activated alumina, silica, titania, cerium oxide (ceria). It is preferable to use one.
[0042]
The method for supporting the noble metal on the carrier is not particularly limited. As a supporting method, an impregnation method in which a support is immersed in a solution containing a metal component, a coprecipitation method in which a precipitant is added to a mixed solution of a support component and a metal component, and a precipitate is formed at the same time, and this is fired, a support After soaking in a metal component, a precipitant is added while stirring to deposit a metal component precipitate on the carrier, and after preparing the metal component precipitate in advance, this and the carrier are kneaded with a ball mill or a blender. And kneading method. Thus, it can be carried out by appropriately selecting from known supporting methods, but it is particularly preferable to use an impregnation method.
[0043]
As the noble metal raw material compound constituting the catalyst of the present invention, any water-soluble compound such as dinitrodiamminate, nitrate and chloride can be used.
[0044]
Further, in addition to the noble metal catalyst component in the exhaust gas purifying catalyst device of the first invention, the second invention and the third invention, in order to improve the adhesion to the carrier, it is selected from the group consisting of activated alumina, boehmite alumina and alumina sol It is preferred to add one of these. Further, in addition to the hydrocarbon adsorbent in the exhaust gas purifying and dissolving catalyst device of the third invention, it is preferable to add silica in order to improve the adhesion with the carrier.
[0045]
The exhaust gas purifying catalyst according to the present invention thus obtained can be used effectively without a carrier, but it is used as a pulverized slurry, coated on the catalyst carrier, and calcined at 400 to 900 ° C. It is preferable. The catalyst carrier can be appropriately selected from known catalyst carriers, and examples thereof include a monolith carrier made of a refractory material and a metal carrier.
[0046]
Therefore, the obtained Pt-supported ZrO2 If desired, one kind selected from the group consisting of activated alumina, boehmite alumina and alumina sol is added to the powder, and it is pulverized in a wet form to form a slurry, which is attached to the catalyst carrier and is in the air at a temperature in the range of 400 to 650 ° C. And / or an exhaust gas purifying catalyst used in the first, second and third inventions by calcination under air flowBCan be obtained.
[0047]
Further, one kind selected from the group consisting of the obtained Pd-supported alumina powder, Pd-supported cerium oxide powder, and Rh-supported alumina powder, if desired, from the group consisting of activated alumina, boehmite alumina, and alumina sol. For the exhaust gas purification used in the second invention by pulverizing into a wet slurry and adhering it to the catalyst carrier and firing in air and / or under air flow at a temperature in the range of 400 to 650 ° C catalystACan be obtained.
[0048]
Furthermore, in order to efficiently express the synergistic action of rhodium and palladium, the catalyst component layer containing palladium is disposed on the lower side (inner layer side) of the coat layer, and the catalyst component layer containing rhodium is located on the upper side of the coat layer. It is preferable to arrange on the (surface layer side). As described above, for example, the following method, sequential coating method, sequential impregnation method or the like is used as a method of disposing the catalyst component on the lower side of the coat layer and on the upper side of the coat layer.
[0049]
Further, silica is added to the hydrocarbon adsorbent and wet pulverized to form a slurry, and this slurry is adhered to the catalyst carrier. Further, the obtained noble metal support selected from the group consisting of Pt, Pd, and Rh is obtained. One powder selected from the group consisting of activated alumina, boehmite alumina, and alumina sol is added to a powder of zirconia oxide (zirconia), activated alumina, silica, titania, cerium oxide (ceria), etc. The slurry is attached to the catalyst carrier to which the hydrocarbon adsorbent has already been attached, and is fired in the air and / or under air flow at a temperature in the range of 400 to 650 ° C., and used in the third invention. Exhaust gas purification catalystCCan be obtained.
[0050]
In order to improve the purification efficiency of the catalyst, the catalyst component layer containing the hydrocarbon adsorbent is disposed on the lower side (inner layer side) of the coat layer, and the catalyst component layer containing the noble metal is disposed on the upper side of the coat layer (surface layer side). ) Is preferable. As described above, for example, the following method, sequential coating method, sequential impregnation method or the like is used as a method of disposing the catalyst component on the lower side of the coat layer and on the upper side of the coat layer.
[0051]
The shape of the catalyst carrier is not particularly limited, but it is usually preferable to use a honeycomb shape, and the catalyst powder is applied to various honeycomb substrates.
As this honeycomb material, cordierite material such as ceramic is generally used, but it is also possible to use a honeycomb material made of a metal material such as ferritic stainless steel, and further, the catalyst component powder itself is formed into a honeycomb shape. It may be molded. By making the catalyst into a honeycomb shape, the contact area between the catalyst and the exhaust gas is increased, and the pressure loss can be suppressed, which is extremely effective when used as an exhaust gas purifying catalyst for automobiles.
[0052]
The amount of the catalyst component coat layer deposited on the honeycomb material is preferably 50 g to 400 g per liter of the catalyst in total for the entire catalyst component.
The more the catalyst component-carrying layer, the better from the standpoint of catalyst activity and catalyst life, but if the coat layer becomes too thick, the reaction gas will not diffuse properly inside the catalyst component-carrying layer, making it impossible to contact the catalyst sufficiently. The effect of increasing the amount of water becomes saturated, and the gas passage resistance also increases. For this reason, the coating layer amount is preferably 50 g to 400 g per liter of the catalyst.
[0053]
In the catalyst device of the second invention,Catalytic deviceThe exhaust gas atmosphere at the inlet is controlled to have an excess oxygen ratio (Z value) of 0.9 to less than 1.0. This is because by setting Pd as the active main component of the catalyst arranged on the upstream side, it is possible to control the HC purification characteristics because the activity when a slightly excessive fuel atmosphere can be increased.Downstream catalyst BHC component of the inlet atmosphereMost downstreamPt-supported ZrO with excellent HC purification activity2 catalystBCan be the target of.
[0054]
The present invention will be described more specifically with reference to the following examples and comparative examples. However, the present invention is not limited to these examples unless it is contrary to the spirit of the present invention.
[0055]
Example 1
The γ-alumina powder was impregnated with an aqueous palladium nitrate solution, dried at 150 ° C. for 12 hours, and then fired at 400 ° C. for 1 hour to obtain a Pd-supported alumina powder (powder A). The Pd concentration of this powder A was 1.7% by weight.
[0056]
Lanthanum 1 mol% (La2OThreeIn terms of 2% by weight) and 32 mol% zirconium (ZrO)2A cerium oxide powder containing 25% by weight in terms of the amount of palladium was impregnated with an aqueous palladium nitrate solution, dried at 150 ° C. for 12 hours, and then calcined at 400 ° C. for 1 hour to obtain Pd-supported cerium oxide (La0.01Zr0. 32Ce0.67Ox) powder (powder B) was obtained. The Pd concentration of this powder B was 0.75% by weight.
[0057]
The above-mentioned powder A146g, powder B100g and nitric acid aqueous solution 254g were put into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid was attached to a cordierite monolith support (1.7 L, 400 cells / in 2), excess slurry in the cells was removed by air flow, dried, and fired at 500 ° C. for 1 hour. This operation was performed twice to obtain catalyst A having a coat weight of 200 g / L-carrier. The amount of palladium supported was 3.53 g / L (100 g / cf).
[0058]
ZrO2The powder was impregnated with an aqueous solution of dinitrodiammine platinum, dried at 150 ° C. for 12 hours, and then calcined at 400 ° C. for 1 hour to obtain Pt-supported ZrO.2A powder (powder C) was obtained. The Pt concentration of this powder C was 1.5% by weight.
[0059]
195 g of the powder C, 5 g of boehmite alumina, and 295 g of an aqueous nitric acid solution were put in a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry was adhered to a cordierite monolith support (1.7 L, 400 cells / square inch), excess slurry in the cells was removed and dried with an air stream, and calcined at 400 ° C. for 1 hour. A catalyst B having a coat layer weight of 225 g / L-support was obtained. The amount of Pt supported was 2.83 g / L (80 g / cf).
[0060]
The catalyst A (upstream catalyst) is arranged upstream of the exhaust, the catalyst B (downstream catalyst) is arranged downstream of the exhaust, the catalyst A inlet has an oxygen excess ratio Z = 0.92, and 2 at the catalyst B inlet. The next air was intermittently added to control Z = 1.2.
[0061]
Example 2
Exhaust gas purifying catalyst device as in Example 1, except that Rh was further added to the catalyst A obtained in Example 1 and a Pd / Rh catalyst (Pd / Rh = 5.3 g / L) was used. Configured and controlled.
[0062]
Example 3
In the catalyst B obtained in Example 1, Pt-supported ZrO2Exhaust gas purifying catalyst device was configured and controlled in the same manner as in Example 1 except that the Pt concentration of the powder was used from 1.5 wt% to 4.8 wt%.
[0063]
Example 4
Example 1 except that the exhaust gas atmosphere at the inlet of the upstream catalyst A obtained in Example 1 is Z = 0.98 and the inlet of the downstream catalyst B obtained in Example 1 is Z = 1.4. The exhaust gas purification catalyst device was constructed and controlled in the same manner as described above.
[0064]
Example 5
Exhaust gas purifying catalyst device was configured and controlled in the same manner as in Example 1 except that the Pd carrying amount of the catalyst A obtained in Example 1 arranged on the exhaust upstream side was 2.83 g / L.
[0065]
Example 6
Exhaust gas purifying catalyst device was configured and controlled in the same manner as in Example 1 except that the Pt carrying amount of the catalyst B obtained in Example 1 arranged on the exhaust downstream side was changed to 1.77 g / L. .
[0066]
Example 7
Exhaust gas purifying catalyst device as in Example 1 except that the Pt carrying amount of the catalyst B obtained in Example 1 arranged on the exhaust downstream side is unchanged and the Pt carrying concentration is changed to 0.5% by weight. Configured and controlled.
[0067]
Example 8
Exhaust gas purifying catalyst device in the same manner as in Example 1 except that the Pt carrying amount of the catalyst B obtained in Example 1 arranged on the exhaust downstream side is unchanged and the Pt carrying concentration is changed to 6.0% by weight. Configured and controlled.
[0068]
Example 9
284 g of ZSM-5 zeolite powder, 600 g of silica sol (solid content 20% by weight), and 10 g of water were put into a magnetic ball mill, and a slurry was obtained through a mixing and grinding process. This slurry was adhered to a cordierite monolith support (0.7 L, 400 cells / in 2), excess slurry in the cells was removed with an air stream, dried, and fired at 500 ° C. for 1 hour. This operation was repeated several times to obtain a catalyst a having a total coat weight of 100 g / L-support.
[0069]
Further, 146 g and 100 g of Pd-supported alumina powder (Pd support concentration 3.4 wt%) and Pd-supported cerium oxide powder (Pd support concentration 1.5 wt%), respectively, and 254 g of nitric acid aqueous solution were put into a magnetic ball mill. A slurry was obtained by mixing and grinding. This slurry was adhered to the catalyst a, excess slurry in the cell was removed by air flow, dried, and calcined at 500 ° C. for 1 hour. This operation was performed twice to obtain a catalyst C having a coating weight of 100 g / L-support of the Pd-supporting layer. The amount of palladium supported was 3.53 g / L (100 g / cf).
[0070]
As shown in FIG. 1, the catalyst A obtained in Example 1 is disposed in the exhaust gas upstream, the catalyst B obtained in Example 1 is disposed downstream of the exhaust, and the catalyst C is disposed immediately before the catalyst B. Then, the oxygen excess rate Z was set to 0.92 at the inlet of the catalyst A, and secondary air was intermittently added at the inlet of the catalyst C to control Z to be 1.2.
[0071]
Example 10
Exhaust gas purification catalyst in the same manner as in Example 9, except that in the catalyst C obtained in Example 9, β zeolite (H type, Si / 2Al = 75) was used as the HC adsorbent instead of ZSM5 zeolite. The device was configured and controlled.
[0072]
Example 11
In catalyst C obtained in Example 9, in addition to ZSM5 zeolite as an HC adsorbent, β zeolite (H type, Si / 2Al = 75) was further added at 100 g / L, and the total amount of zeolite was 200 g / L. Exhaust gas purifying and dissolving catalyst device was constructed and controlled in the same manner as in Example 9 except that.
[0073]
Example 12
In the catalyst C obtained in Example 9, except that a Pd / Rh catalyst layer (Pd / Rh = 4.24 g / L-5 / 1) in which Rh was further added in addition to Pd of the noble metal coating layer was used. The exhaust gas purifying catalyst device was configured and controlled in the same manner as in Example 9.
[0074]
Example 13
In the catalyst C obtained in Example 9, the Pd / Rh catalyst layer (Pt / Rh = 4.24 g / L-5 / 1) was used except that the Pd of the noble metal coating layer was changed to Pt. The same exhaust gas purifying catalyst device as in No. 12 was constructed and controlled.
[0075]
Example 14
Except that the catalyst C obtained in Example 9 was used by changing the ZSM5 zeolite content to 30 g / L as the HC adsorbent, the exhaust gas purification catalyst device was configured in the same manner as in Example 9, Controlled.
[0076]
Example 15
In the catalyst C obtained in Example 9, except that the amount of Pd of the noble metal coat layer was changed to 0.8 g / L, the catalyst device for exhaust gas purification was configured and controlled in the same manner as in Example 9. did.
[0077]
Comparative Example 1
The catalyst B obtained in Example 1 disposed downstream of the exhaust was converted into a Pd catalyst (Pd = 5.3 g / L, Pd-supported ZrO). 2 Except for the use), an exhaust gas purifying catalyst device was constructed and controlled in the same manner as in Example 1.
[0078]
Comparative Example 2
The Pt support material of the catalyst B obtained in Example 1 disposed downstream of the exhaust was changed to ZrO. 2 Except for changing to γ-alumina, an exhaust gas purifying catalyst device was constructed and controlled in the same manner as in Example 1.
[0079]
Reference example 1
Exhaust gas purification catalyst device was configured and controlled in the same manner as in Example 1 except that the exhaust gas atmosphere at the inlet of the catalyst A obtained in Example 1 arranged upstream of the exhaust gas was set to Z = 0.8.
[0080]
Reference example 2
Exhaust gas purifying catalyst device was configured and controlled in the same manner as in Example 1 except that the exhaust gas atmosphere at the inlet of the catalyst A obtained in Example 1 disposed upstream of the exhaust gas was Z = 1.2.
[0081]
Reference example 3
Exhaust gas purifying catalyst device was configured and controlled in the same manner as in Example 1 except that the inlet atmosphere of the catalyst B obtained in Example 1 disposed downstream of the exhaust gas was set to Z = 0.95.
[0082]
Reference example 4
Exhaust gas purifying catalyst device was configured and controlled in the same manner as in Example 1 except that the inlet atmosphere of the catalyst B obtained in Example 1 disposed downstream of the exhaust gas was changed to Z = 1.60.
[0083]
Reference Example 5
Exhaust gas purifying catalyst device was configured and controlled in the same manner as in Example 1 except that secondary air was continuously added in the inlet atmosphere of the catalyst B obtained in Example 1 disposed downstream of the exhaust. .
[0084]
Reference Example 6
In the catalyst B in Example 1, the amount of Pt supported was 2.83 g / L and the concentration of Pt supported was 1.5% by weight, and the exhaust gas purification catalyst device was configured and controlled on the exhaust downstream side.
[0085]
Test example
Examples 1 to 15And Comparative Examples 1 and 2, Reference Examples 1 and6The exhaust gas purification catalyst device (FIG. 1) was evaluated for catalytic activity under the following evaluation conditions.
[0086]
Evaluation conditions: Vehicle evaluation (North America LA4 mode, B back)
Engine displacement 2400cc (4 in-line cylinders)
IW 3250 lbs
Fuel Unleaded gasoline
[0087]
Examples 1 to 1 above5And Comparative Examples 1 and 2, Reference Examples 1 and6The amount of noble metal supported (palladium, rhodium, platinum content in 1 L of catalyst), the control method, and the catalyst activity evaluation result of the exhaust gas purification catalyst device examined in (1) Table 1 summarizes the average conversion rate (%) as HC purification performance.
[0088]
[Table 1]
【The invention's effect】
As described above, the catalyst device of the present invention has the effect of improving the HC purification performance, and in particular, significantly improving the purification of HC components that have not been conventionally purified.
[0090]
Furthermore, the method of the present invention is configured to control the exhaust gas atmosphere at the upstream side catalyst inlet and the downstream side catalyst inlet to an appropriate oxygen excess rate, respectively, so that the HC purification performance is improved. The purification of the HC component, which was the purification, is remarkably improved and the effect of maintaining it is achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an arrangement of an exhaust gas purifying catalyst device of the present invention.
Claims (9)
最下流に配置された触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ2 ）とを含み、かつ触媒成分であるＰｔがＺｒＯ2にのみ担持されている一体構造型触媒であり、
排気ガス浄化用触媒装置入口での排気ガス雰囲気を制御する手段と、前記最下流の触媒Ｂの入口に空気又は酸素を断続的に導入して前記最下流の触媒Ｂの入口の排気ガス雰囲気を制御する手段とを配置してなることを特徴とする排気ガス浄化用触媒装置。 An exhaust gas purifying catalyst device in which a plurality of catalysts are arranged ,
Catalyst B which is arranged at the most downstream comprises Pt and a zirconia (ZrO 2) as a catalyst component, and Ri integral structure type catalyst der the Pt as a catalyst component is supported only on ZrO 2,
Means for controlling the exhaust gas atmosphere at the inlet of the exhaust gas purifying catalyst device, and intermittently introducing air or oxygen into the inlet of the most downstream catalyst B to provide an exhaust gas atmosphere at the inlet of the most downstream catalyst B. And means for controlling the exhaust gas purification catalyst device.
最下流に配置された触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ2 ）とを含み、かつ触媒成分であるＰｔがＺｒＯ2にのみ担持されている一体構造型触媒であり、
更に排気ガス流れに対し最上流側に触媒成分としてＰｄ又は、ＰｄとＲｈを含む触媒Ａを配置し、
排気ガス浄化用触媒装置入口での排気ガス雰囲気を制御する手段と、前記最下流の触媒Ｂの入口に空気又は酸素を断続的に導入して前記最下流の触媒Ｂの入口の排気ガス雰囲気を制御する手段とを配置してなることを特徴とする、排気ガス浄化用触媒装置。 An exhaust gas purifying catalyst device in which a plurality of catalysts are arranged ,
The catalyst B arranged at the most downstream side contains Pt and zirconia (ZrO 2 ) as catalyst components , and the catalyst component Pt is an integral structure type catalyst supported only on ZrO 2 ;
Furthermore, the catalyst A containing Pd or Pd and Rh as a catalyst component is arranged on the most upstream side with respect to the exhaust gas flow ,
Means for controlling the exhaust gas atmosphere at the inlet of the exhaust gas purifying catalyst device, and intermittently introducing air or oxygen into the inlet of the most downstream catalyst B, thereby providing an exhaust gas atmosphere at the inlet of the most downstream catalyst B. And means for controlling the exhaust gas purification catalyst device.
最下流に配置された触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ2 ）とを含み、かつ触媒成分であるＰｔがＺｒＯ2にのみ担持されている一体構造型触媒であり、
更に排気ガス流れに対し最上流側に触媒成分としてＰｄ又は、ＰｄとＲｈを含む触媒Ａを配置し、
更に炭化水素吸着材と、Ｐｔ，Ｐｄ及びＲｈから成る群より選ばれる少なくとも一種以上の貴金属とを含む触媒Ｃを、前記最下流の触媒Ｂと前記最上流の触媒Ａとの間に配置し、
排気ガス浄化用触媒装置入口での排気ガス雰囲気を制御する手段と、前記最下流の触媒Ｂの入口に空気又は酸素を断続的に導入して前記最下流の触媒Ｂの入口の排気ガス雰囲気を制御する手段とを配置してなることを特徴とする、排気ガス浄化用触媒装置。 An exhaust gas purifying catalyst device in which a plurality of catalysts are arranged ,
The catalyst B arranged at the most downstream side contains Pt and zirconia (ZrO 2 ) as catalyst components , and the catalyst component Pt is an integral structure type catalyst supported only on ZrO 2 ;
Furthermore, the catalyst A containing Pd or Pd and Rh as a catalyst component is arranged on the most upstream side with respect to the exhaust gas flow,
Further, a catalyst C containing a hydrocarbon adsorbent and at least one or more noble metals selected from the group consisting of Pt, Pd and Rh is disposed between the most downstream catalyst B and the most upstream catalyst A,
Means for controlling the exhaust gas atmosphere at the inlet of the exhaust gas purifying catalyst device, and intermittently introducing air or oxygen into the inlet of the most downstream catalyst B, thereby providing an exhaust gas atmosphere at the inlet of the most downstream catalyst B. And means for controlling the exhaust gas purification catalyst device.
内燃機関から排出される排気ガスを、触媒を複数配置してなり、排気ガス流れに対して最下流の触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ 2 ）を含み、かつ触媒成分であるＰｔがＺｒＯ2 にのみ担持されている一体構造型触媒である排気ガス浄化用触媒装置と接触させ、
前記排気ガス浄化用触媒装置入口での排気ガス雰囲気を、酸素過剰率（Ｚ値）にして０．９＜Ｚ＜１．０の燃料過剰雰囲気に制御し、
かつ前記最下流の触媒Ｂの入口に空気又は酸素を断続的に導入し、前記最下流の触媒Ｂの入口の排気ガス雰囲気を、酸素過剰率（Ｚ値）にして１．０＜Ｚ＜１．５の範囲で制御することを特徴とする、排気ガス浄化方法。An exhaust gas purification method for simultaneously purifying carbon monoxide, hydrocarbons and nitrogen oxides in exhaust gas,
The exhaust gas discharged from the internal combustion engine is formed by arranging a plurality of catalysts, and the catalyst B at the most downstream side with respect to the exhaust gas flow has Pt and zirconia (ZrO 2) as catalyst components. ), And Pt which is a catalyst component is brought into contact with an exhaust gas purifying catalyst device which is a monolithic catalyst in which only ZrO 2 is supported ,
The exhaust gas atmosphere at the exhaust gas purification catalyst inlet is controlled to an excess fuel atmosphere of 0.9 <Z <1.0 with an oxygen excess rate (Z value),
And wherein the intermittently introducing air or oxygen into the inlet of the most downstream catalyst B, wherein the inlet of the exhaust gas atmosphere downstream of the catalyst B, and the oxygen excess ratio (Z value) 1.0 <Z <1 The exhaust gas purification method is characterized in that it is controlled within a range of .5.
内燃機関から排出される排気ガスを、触媒を複数配置してなり、排気ガス流れに対して最下流の触媒Ｂが触媒成分としてＰｔとジルコニア（ＺｒＯ2 ）を含み、活性種であるＰｔがＺｒＯ2 にのみ担持されている一体構造型触媒であり、更に排気ガス流れに対して最上流側に触媒成分としてＰｄ又は、ＰｄとＲｈを含む触媒Ａを配置してなる排気ガス浄化用触媒装置と接触させ、
前記排気ガス浄化用触媒装置入口での排気ガス雰囲気を、酸素過剰率（Ｚ値）にして０．９＜Ｚ＜１．０の燃料過剰雰囲気に制御し、
かつ前記最下流の触媒Ｂの入口に空気又は酸素を断続的に導入し、前記下流側触媒入口の排気ガス雰囲気を、酸素過剰率（Ｚ値）にして１．０＜Ｚ＜１．５の範囲で制御することを特徴とする排気ガス浄化方法。An exhaust gas purification method for simultaneously purifying carbon monoxide, hydrocarbons and nitrogen oxides in exhaust gas,
Exhaust gas discharged from the internal combustion engine is formed by arranging a plurality of catalysts, the catalyst B which is the most downstream with respect to the exhaust gas flow contains Pt and zirconia (ZrO 2 ) as catalyst components , and Pt which is an active species is ZrO And a catalyst device for purifying exhaust gas , wherein the catalyst is a monolithic structure type catalyst supported only on 2 and further comprises a catalyst A containing Pd or Pd and Rh as a catalyst component on the most upstream side with respect to the exhaust gas flow ; Contact ,
The exhaust gas atmosphere at the exhaust gas purification catalyst inlet is controlled to an excess fuel atmosphere of 0.9 <Z <1.0 with an oxygen excess rate (Z value),
In addition , air or oxygen is intermittently introduced into the inlet of the most downstream catalyst B , and the exhaust gas atmosphere at the downstream catalyst inlet is set to an oxygen excess ratio (Z value) of 1.0 <Z <1.5. A method for purifying exhaust gas, characterized by being controlled by a range.
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