JP3835436B2 - Exhaust gas purification method and exhaust gas purification catalyst - Google Patents

Description

【００５９】
（実施例１）
＜ゼオライト＞
市販のモルデナイト粉末（「 HSZ690HOA」東ソー（株）製、Si／Al比＝ 200）を1000部用意し、純水5000部にオキシ硝酸ジルコニウム 145部を溶解した水溶液に混合して30分間撹拌した。その後25％アンモニア水溶液 200部を混合し、さらに30分間混合した。12時間熟成した後濾過・水洗し、大気中にて 110℃で２時間乾燥した。
【００６０】
得られた粉末全量を１規定の硫酸水溶液5000部中に混合し、１時間撹拌した後濾過して、大気中 110℃で２時間乾燥し、さらに大気中 700℃で３時間焼成した。これにより、モルデナイト粉末表面に超強酸化ジルコニア層を形成した。
【００６１】
＜多孔質担体＞
チタニア粉末 100部と、４重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持チタニア（Pt／TiO₂）粉末を調製した。担持されたPtの担持量は、２重量％である。
【００６２】
＜酸素放出材＞
セリア−ジルコニア複合酸化物（Zr／Ce＝１／４）粉末 100部と、４重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持 CZS（Pt／CZS ）粉末を調製した。担持されたPtの担持量は、２重量％である。
【００６３】
＜コーティング＞
超強酸化ジルコニア層をもつモルデナイト粉末90部と、Pt／TiO₂粉末60部と、Pt／CZS 粉末30部と、純水 200部及びチタニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そしてコージェライト製のハニカム担体基材（ 400セル／in² ，容積 1.7Ｌ）を用意し、スラリー中に浸漬後引き上げて余分なスラリーを吹き払い、 100℃で２時間乾燥後 500℃で２時間焼成して実施例１の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【００６４】
（実施例２）
＜ゼオライト＞
実施例１と同様である。
【００６５】
＜多孔質担体＞
チタニア粉末の代わりにシリカ粉末を 100部用いた以外は実施例１と同様にして、Pt担持シリカ（Pt／SiO₂）粉末を調製した。
【００６６】
＜酸素放出材＞
実施例１と同様である。
【００６７】
＜コーティング＞
Pt担持チタニア粉末の代わりにPt／SiO₂粉末を60部用いたこと、及びチタニアゾルの代わりにシリカゾル（固形分35％）を55部用いたこと以外は実施例１と同様にして、実施例２の触媒を調製した。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【００６８】
（実施例３）
＜ゼオライト＞
実施例１と同様である。
【００６９】
＜多孔質担体＞
チタニア粉末の代わりにジルコニア粉末を 100部用いた以外は実施例１と同様にして、Pt担持ジルコニア（Pt／ZrO₂）粉末を調製した。
【００７０】
＜酸素放出材＞
実施例１と同様である。
【００７１】
＜コーティング＞
Pt担持チタニア粉末の代わりにPt／ZrO₂粉末を60部用いたこと、及びチタニアゾルの代わりにジルコニアゾル（固形分35％）を55部用いたこと以外は実施例１と同様にして、実施例３の触媒を調製した。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【００７２】
（実施例４）
＜ゼオライト＞
モルデナイト粉末の代わりにＹ型ゼオライト粉末（「 HSZ390HUA」東ソー（株）製、Si／Al比＝ 400）を同量用いたこと以外は実施例１と同様にして、Ｙ型ゼオライト粉末表面に超強酸化ジルコニア層を形成した。
【００７３】
＜多孔質担体＞
実施例１と同様である。
【００７４】
＜酸素放出材＞
実施例１と同様である。
【００７５】
＜コーティング＞
超強酸化ジルコニア層をもつモルデナイト粉末の代わりに超強酸化ジルコニア層をもつＹ型ゼオライト粉末を90部用いたこと以外は実施例１と同様にして、実施例４の触媒を調製した。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【００７６】
（実施例５）
＜ゼオライト＞
モルデナイト粉末の代わりにZSM-５型ゼオライト粉末（「 HSZ890HOA」東ソー（株）製、Si／Al比＝2000）を同量用いたこと以外は実施例１と同様にして、ZSM-５型ゼオライト粉末表面に超強酸化ジルコニア層を形成した。
【００７７】
＜多孔質担体＞
実施例１と同様である。
【００７８】
＜酸素放出材＞
実施例１と同様である。
【００７９】
＜コーティング＞
超強酸化ジルコニア層をもつモルデナイト粉末の代わりに超強酸化ジルコニア層をもつZSM-５型ゼオライト粉末を90部用いたこと以外は実施例１と同様にして、実施例５の触媒を調製した。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【００８０】
（実施例６）
＜ゼオライト＞
実施例１と同様である。
【００８１】
＜多孔質担体＞
実施例１と同様である。
【００８２】
＜酸素放出材＞
セリア−ジルコニア複合酸化物（Zr／Ce＝１／４）粉末 500部を、純水2000部にオキシ硝酸ジルコニウム 300部を溶解した水溶液に混合して30分間撹拌した。その後25％アンモニア水溶液 300部を混合し、さらに30分間混合した。12時間熟成した後濾過・水洗し、大気中にて 110℃で２時間乾燥した。その後大気中にて 500℃で３時間焼成し、ジルコニア層をもつ CZS（Zr-CZS）粉末を調製した。
【００８３】
次に、Zr-CZS粉末 100部と、４重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持Zr-CZS（Pt／Zr-CZS）粉末を調製した。担持されたPtの担持量は、２重量％である。
【００８４】
＜コーティング＞
実施例１と同様の超強酸化ジルコニア層をもつモルデナイト粉末90部と、実施例３と同様のPt／TiO₂粉末60部と、Pt／Zr-CZS粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして実施例６の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【００８５】
（実施例７）
＜ゼオライト＞
実施例１と同様である。
【００８６】
＜多孔質担体＞
実施例３と同様である。
【００８７】
＜酸素放出材＞
セリア−ジルコニア複合酸化物（Zr／Ce＝１／４）粉末 500部を、純水2000部にオキシ硝酸ジルコニウム 300部を溶解した水溶液に混合して30分間撹拌した。その後25％アンモニア水溶液 300部を混合し、さらに30分間混合した。12時間熟成した後濾過・水洗し、大気中にて 110℃で２時間乾燥した。
【００８８】
次に、得られたZr-CZS粉末全量を１規定の硫酸水溶液5000部に混合して１時間撹拌し、濾過後大気中にて 110℃で２時間乾燥し、さらに大気中にて 700℃で３時間焼成して超強酸化Zr-CZS粉末を調製した。
【００８９】
次に、超強酸化Zr-CZS粉末 100部と、４重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持超強酸化Zr-CZS（Pt／超強酸化Zr-CZS）粉末を調製した。担持されたPtの担持量は、２重量％である。
【００９０】
＜コーティング＞
実施例１と同様の超強酸化ジルコニア層形成モルデナイト粉末90部と、実施例３と同様のPt／ZrO₂粉末60部と、Pt／超強酸化Zr-CZS粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして実施例７の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【００９１】
（実施例８）
＜ゼオライト＞
実施例１と同様である。
【００９２】
＜多孔質担体＞
活性アルミナ（比表面積 200m²／ｇ）粉末 500部を、純水2000部にオキシ硝酸ジルコニウム 300部を溶解した水溶液に混合して30分間撹拌した。その後25％アンモニア水溶液 300部を混合し、さらに30分間混合した。12時間熟成した後濾過・水洗し、大気中にて 110℃で２時間乾燥した。その後大気中にて 500℃で３時間焼成し、ジルコニア層をもつアルミナ（Zr-Al₂O₃）粉末を調製した。
【００９３】
次に、Zr-Al₂O₃粉末 100部と、４重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持Zr−アルミナ（Pt／Zr-Al₂O₃）粉末を調製した。担持されたPtの担持量は、２重量％である。
【００９４】
＜酸素放出材＞
実施例１と同様である。
【００９５】
＜コーティング＞
実施例１と同様の超強酸化ジルコニア層をもつモルデナイト粉末90部と、上記Pt／Zr-Al₂O₃粉末60部と、実施例１と同様のPt／CZS 粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして実施例８の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【００９６】
（実施例９）
＜ゼオライト＞
実施例１と同様である。
【００９７】
＜多孔質担体＞
活性アルミナ（比表面積 200m²／ｇ）粉末 500部を、純水2000部にオキシ硝酸ジルコニウム 300部を溶解した水溶液に混合して30分間撹拌した。その後25％アンモニア水溶液 300部を混合し、さらに30分間混合した。12時間熟成した後濾過・水洗し、大気中にて 110℃で２時間乾燥した。
【００９８】
次に、得られたZr-Al₂O₃粉末全量を１規定の硫酸水溶液5000部に混合して１時間撹拌し、濾過後大気中にて 110℃で２時間乾燥し、さらに大気中にて 700℃で３時間焼成して、超強酸化ジルコニア層形成アルミナ（超強酸化Zr-Al₂O₃）粉末を調製した。
【００９９】
次に、超強酸化Zr-Al₂O₃粉末 100部と、４重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持超強酸化Zr−アルミナ粉末（Pt／超強酸化Zr-Al₂O₃）を調製した。担持されたPtの担持量は、２重量％である。
【０１００】
＜酸素放出材＞
実施例１と同様である。
【０１０１】
＜コーティング＞
実施例１と同様の超強酸化ジルコニア層をもつモルデナイト粉末90部と、上記Pt／超強酸化Zr-Al₂O₃粉末60部と、実施例１と同様のPt／CZS 粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして実施例９の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１０２】
（実施例10）
＜ゼオライト＞
実施例１と同様である。
【０１０３】
＜多孔質担体＞
活性アルミナ（比表面積 200m²／ｇ）粉末 500部を１規定の硫酸水溶液3000部に混合し、３時間撹拌した後濾過して、大気中にて 110℃で２時間乾燥した。その後大気中にて 700℃で３時間焼成し、超強酸化アルミナ（超強酸化Al₂O₃ ）粉末を調製した。
【０１０４】
次に、超強酸化Al₂O₃ 粉末 100部と、４重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持超強酸化アルミナ（Pt／超強酸化Al₂O₃ ）粉末を調製した。担持されたPtの担持量は、２重量％である。
【０１０５】
＜酸素放出材＞
実施例１と同様である。
【０１０６】
＜コーティング＞
実施例１と同様の超強酸化ジルコニア層をもつモルデナイト粉末90部と、上記Pt／超強酸化Al₂O₃ 粉末60部と、実施例１と同様のPt／CZS 粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして実施例10の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１０７】
（実施例11）
チタニア粉末 100部と、６重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持チタニア（）Pt／TiO₂粉末を調製した。担持されたPtの担持量は、３重量％である。
【０１０８】
実施例１と同様の超強酸化ジルコニア層をもつモルデナイト粉末90部と、得られたPt／TiO₂粉末60部と、セリア−ジルコニア複合酸化物（CZS ，Zr／Ce＝１／４）粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして実施例11の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１０９】
（実施例12）
活性アルミナ（比表面積 200m²／ｇ）粉末 100部と、４重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt／Al₂O₃ 粉末を調製した。担持されたPtの担持量は、２重量％である。
【０１１０】
実施例１と同様の超強酸化ジルコニア層をもつモルデナイト粉末90部と、得られたPt／Al₂O₃ 粉末60部と、実施例１と同様のPt／CZS 粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして実施例12の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１１１】
（比較例１）
市販のモルデナイト粉末（「 HSZ690HOA」東ソー（株）製、Si／Al比＝ 200）90部と、実施例１と同様のPt／TiO₂粉末60部と、実施例１と同様のPt／CZS 粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして比較例１の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１１２】
（比較例２）
市販のモルデナイト粉末（「 HSZ660HOA」東ソー（株）製、Si／Al比＝30）を 1000部用意し、純水5000部にオキシ硝酸ジルコニウム 145部を溶解した水溶液に混合して30分間撹拌した。その後25％アンモニア水溶液 200部を混合し、さらに30分間混合した。12時間熟成した後濾過・水洗し、大気中にて 110℃で２時間乾燥した。
【０１１３】
得られた粉末全量を１規定の硫酸水溶液5000部中に混合し、１時間撹拌した後濾過して、大気中 110℃で２時間乾燥し、さらに大気中 700℃で３時間焼成した。これにより、モルデナイト粉末表面に超強酸化ジルコニア層を形成した。
【０１１４】
得られた超強酸化ジルコニア層をもつモルデナイト粉末90部と、実施例１と同様のPt／TiO₂末60部と、実施例１と同様のPt／CZS 粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして比較例２の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１１５】
（比較例３）
実施例１と同様の超強酸化ジルコニア層をもつモルデナイト粉末 100部と、２重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt担持超強酸化ジルコニア層をもつモルデナイト（Pt／超強酸化ZrO₂層形成−モルデナイト）粉末を調製した。担持されたPtの担持量は、１重量％である。
【０１１６】
また、チタニア粉末 100部と、２重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt／TiO₂粉末を調製した。担持されたPtの担持量は、１重量％である。
【０１１７】
さらに、セリア−ジルコニア複合酸化物（Zr／Ce＝１／４）粉末 100部と、２重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部とを混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成してPt／CZS 粉末を調製した。担持されたPtの担持量は、１重量％である。
【０１１８】
Pt／超強酸化ZrO₂層形成−モルデナイト粉末90部と、Pt／TiO₂粉末60部と、Pt／CZS 粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして比較例３の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１１９】
（比較例４）
市販のモルデナイト粉末（「 HSZ660HOA」東ソー（株）製、Si／Al比＝30）90部と、実施例１と同様のPt／TiO₂粉末60部と、実施例１と同様のPt／CZS 粉末30部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして比較例４の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１２０】
（比較例５）
ゼオライトを用いず、実施例１と同様のPt／TiO₂粉末60部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして比較例５の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１２１】
（比較例６）
実施例１と同様の超強酸化ジルコニア層をもつモルデナイト粉末90部と、実施例１と同様のPt／TiO₂粉末60部と、純水 200部及びジルコニアゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そして実施例１と同様のハニカム担体基材を用意し、実施例１と同様にコートして比較例６の触媒を得た。コート量は担体基材１Ｌ当たり 180ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.8ｇである。
【０１２２】
（評価試験）
上記したそれぞれの触媒を2400cc直列４気筒のディーゼルエンジンの排気系に装着し、回転数3600 rpm一定で、負荷により触媒入りガス温度が 600℃になるように調整して、25時間の耐久試験を行った。
【０１２３】
耐久試験後の各触媒をそれぞれ耐久試験と同様のエンジンの排気系に装着し、図１に示すように回転数が1000〜2500 rpmの範囲で変化するように負荷を変化させ、排ガス中に軽油を 300〜1200ppmCの範囲で添加しながら、HCとNOの浄化率をそれぞれ測定した。結果を図２に示す。
【０１２４】
図２より、各実施例の触媒は比較例の触媒に比べて耐久後のNO浄化率及びHC浄化率が高く、耐久性に優れていることがわかる。
【０１２５】
さらに詳しく解析すると、実施例11の触媒は実施例１に比べて浄化率が低い。この差は酸素放出材にPtの担持の有無の差に起因し、酸素放出材にもPtを担持するのが好ましいことがわかる。
【０１２６】
実施例８の触媒は実施例１に比べて浄化率が低い。この差は多孔質酸化物の種類の違いに起因し、ジルコニア層をもつアルミナよりチタニアの方が好ましいことがわかる。
【０１２７】
実施例３と実施例７とを比較すると、実施例７の触媒の方が浄化率が高い。つまり酸素放出材のコート層を超強酸化することが好ましいことがわかる。また実施例８と実施例９の比較より、多孔質担体を超強酸化することも好ましいことがわかる。
【０１２８】
そして比較例１では、ゼオライトが超強酸化されていないために実施例１に比べて浄化率が低く、比較例２及び比較例４ではゼオライトのSi／Al比が30と小さいために浄化率が低い。また比較例３ではゼオライトにPtを担持しているために浄化率が低い。なお、比較例２と比較例４では比較例２の方が浄化率が高いが、これはゼオライトの超強酸化ジルコニア層の有無の差に起因し、Si／Al比が小さくとも超強酸化ジルコニア層を形成する方が好ましいことがわかる。
【０１２９】
さらに比較例５ではゼオライトも酸素放出材も存在しないために浄化率が極端に低く、比較例６では酸素放出材をもたないために実施例１に比べて浄化率が低くなっている。
【０１３０】
すなわち、これらの効果の差は担体の構成の差に起因するものであり、本発明の触媒の構成とすることによりNO_x 浄化能の耐久性が改善されることが明らかである。
【０１３１】
（参考例１）
＜超強酸酸化物層の形成＞
市販のモルデナイト粉末（「 HSZ690HOA」東ソー（株）製、Si／Al比＝ 200）を1000部用意し、純水5000部にオキシ硝酸ジルコニウム 145部を溶解した水溶液に混合して30分間撹拌した。その後25％アンモニア水溶液 200部を混合し、さらに30分間混合した。12時間熟成した後濾過・水洗し、大気中にて 110℃で２時間乾燥した。
【０１３２】
得られた粉末全量を１規定の硫酸水溶液5000部中に混合し、１時間撹拌した後濾過して、大気中 110℃で２時間乾燥し、さらに大気中 700℃で３時間焼成した。これにより、モルデナイト粉末表面に超強酸化ジルコニア層を形成した。
【０１３３】
＜貴金属の担持＞
上記により得られた超強酸化ジルコニア層をもつモルデナイト粉末 100部と、１重量％のヘキサアンミン白金水酸塩水溶液 100部及び純水 200部と混合し、１時間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成した。これにより担持されたPtの担持量は１重量％である。
【０１３４】
＜コーティング＞
Ptが担持され超強酸化ジルコニア層をもつモルデナイト粉末 150部と、純水 200部及びシリカゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そしてコージェライト製のハニカム担体基材（容積 1.5Ｌ）を用意し、スラリー中に浸漬後引き上げて余分なスラリーを吹き払い、 100℃で２時間乾燥後 500℃で２時間焼成して参考例１の触媒を得た。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１３５】
（参考例２）
オキシ硝酸ジルコニウムの代わりにオキシ硝酸チタニウムを 145部用いたこと以外は参考例１と同様にしてモルデナイト粉末表面に超強酸化チタニア層を形成した。
【０１３６】
この超強酸チタニア層をもつモルデナイト粉末を用い、参考例１と同様にして貴金属を担持するとともにコーティングを行い、参考例２の触媒を調製した。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１３７】
（参考例３）
＜超強酸酸化物層の形成＞
市販のモルデナイト粉末（「 HSZ690HOA」東ソー（株）製、Si／Al比＝ 200） 150部と、固形分30重量％のジルコニアゾル33部とを混合し、30分間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成した。
【０１３８】
得られた粉末1000部を１規定の硫酸水溶液5000部中に混合し、１時間撹拌した後濾過して、大気中 110℃で２時間乾燥し、さらに大気中 700℃で３時間焼成した。これにより、モルデナイト粉末表面に超強酸化ジルコニア層を形成した。
【０１３９】
この超強酸化ジルコニア層をもつモルデナイト粉末を用い、参考例１と同様にして貴金属を担持するとともにコーティングを行い、参考例３の触媒を調製した。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１４０】
（参考例４）
＜超強酸酸化物層の形成＞
市販のモルデナイト粉末（「 HSZ690HOA」東ソー（株）製、Si／Al比＝ 200） 150部と、固形分30重量％のチタニアゾル33部とを混合し、30分間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成した。
【０１４１】
得られた粉末1000部を１規定の硫酸水溶液5000部中に混合し、１時間撹拌した後濾過して、大気中 110℃で２時間乾燥し、さらに大気中 700℃で３時間焼成した。これにより、モルデナイト粉末表面に超強酸化チタニア層を形成した。
【０１４２】
この超強酸化チタニア層をもつモルデナイト粉末を用い、参考例１と同様にして貴金属を担持するとともにコーティングを行い、参考例４の触媒を調製した。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１４３】
（参考例５）
＜超強酸酸化物層の形成＞
市販のモルデナイト粉末（「 HSZ690HOA」東ソー（株）製、Si／Al比＝ 200） 150部と、固形分30重量％のシリカゾル33部とを混合し、30分間撹拌した。その後 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成した。
【０１４４】
得られた粉末1000部を１規定の硫酸水溶液5000部中に混合し、１時間撹拌した後濾過して、大気中 110℃で２時間乾燥し、さらに大気中 700℃で３時間焼成した。これにより、モルデナイト粉末表面に超強酸化シリカ層を形成した。
【０１４５】
この超強酸化シリカ層をもつモルデナイト粉末を用い、参考例１と同様にして貴金属を担持するとともにコーティングを行い、参考例５の触媒を調製した。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１４６】
（参考例６）
モルデナイト粉末の代わりにＹ型ゼオライト粉末（「 HSZ390HUA」東ソー（株）製、Si／Al比＝ 400）を同量用いたこと以外は参考例１と同様にして、Ｙ型ゼオライト粉末表面に超強酸化ジルコニア層を形成した。
【０１４７】
この超強酸化ジルコニア層をもつＹ型ゼオライト粉末を用い、参考例１と同様にして貴金属を担持するとともにコーティングを行い、参考例６の触媒を調製した。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１４８】
（参考例７）
モルデナイト粉末の代わりにZSM-５型ゼオライト粉末（「 HSZ890HOA」東ソー（株）製、Si／Al比＝2000）を同量用いたこと以外は参考例１と同様にして、ZSM-５型ゼオライト粉末表面に超強酸化ジルコニア層を形成した。
【０１４９】
この超強酸化ジルコニア層をもつZSM-５型ゼオライト粉末を用い、参考例１と同様にして貴金属を担持するとともにコーティングを行い、参考例７の触媒を調製した。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１５０】
（参考例８）
参考例１と同様のモルデナイト粉末 100部と、１重量％のヘキサアンミン白金水酸塩水溶液 100部と、純水 200部とを混合し、１時間撹拌後、 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成した。これによりPt担持モルデナイト粉末を調製した。
【０１５１】
次に、Pt担持モルデナイト粉末 150部と、純水 200部及びシリカゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そしてコージェライト製のハニカム担体基材（容積 1.5Ｌ）を用意し、スラリー中に浸漬後引き上げて余分なスラリーを吹き払い、 100℃で２時間乾燥後 500℃で２時間焼成して参考例８の触媒を得た。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１５２】
（参考例９）
市販のモルデナイト粉末（「 HSZ660HOA」東ソー（株）製、Si／Al比＝30） 100部と、１重量％のヘキサアンミン白金水酸塩水溶液 100部と、純水 200部とを混合し、１時間撹拌後、 100℃で加熱し続けて水分を蒸発乾固させ、 120℃で２時間乾燥後さらに 300℃で２時間焼成した。これによりPt担持モルデナイト粉末を調製した。
【０１５３】
次に、Pt担持モルデナイト粉末 150部と、純水 200部及びシリカゾル（固形分35％）55部とを混合し、撹拌してスラリーを調製した。そしてコージェライト製のハニカム担体基材（容積 1.5Ｌ）を用意し、スラリー中に浸漬後引き上げて余分なスラリーを吹き払い、 100℃で２時間乾燥後 500℃で２時間焼成して参考例９の触媒を得た。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１５４】
（参考例10）
ゼオライト粉末として、モルデナイト粉末（「 HSZ660HOA」東ソー（株）製、Si／Al比＝30）を同量用いたこと以外は参考例１と同様にして、モルデナイト粉末表面に超強酸化ジルコニア層を形成した。
【０１５５】
この超強酸化ジルコニア層をもつモルデナイト粉末を用い、参考例１と同様にして貴金属を担持するとともにコーティングを行い、参考例10の触媒を調製した。コート量は担体基材１Ｌ当たり 150ｇであり、Ptの担持量は担体基材１Ｌ当たり 1.5ｇである。
【０１５６】
（評価試験）
上記したそれぞれの触媒を2400cc直列４気筒のディーゼルエンジンの排気系に装着し、回転数3600 rpm一定で、負荷により触媒入りガス温度が 600℃になるように調整して、25時間の耐久試験を行った。
【０１５７】
耐久試験後の各触媒をそれぞれ耐久試験と同様のエンジンの排気系に装着し、図１に示すように回転数が1000〜2500 rpmの範囲で変化するように負荷を変化させ、排ガス中に軽油を 300〜1200ppmCの範囲で添加しながら、HCとNOの最大浄化率をそれぞれ測定した。結果を図３に示す。
【０１５８】
図３より、参考例１〜７の触媒は参考例８〜10の触媒に比べてHC浄化率及びNO浄化率の両方共に優れた結果を示している。そして参考例１〜３の触媒が参考例８より格段に優れた浄化率を示し、超強酸酸化物層の存在が浄化率の向上に著しく寄与していることがわかる。また参考例１〜７の触媒では、耐久試験前後の浄化性能の差はほとんどなく、耐久性にも優れていた。
【０１５９】
一方、参考例10の触媒では、超強酸酸化物層をもつため参考例８，９に比べれば高い浄化率を示しているが、参考例１〜７に比べると浄化率が低い。因みに耐久試験前には参考例10の触媒は参考例１よりもやや高い浄化率を示していたことを考慮すると、参考例10の触媒では、ゼオライトのSi／Al比が小さいために、耐久試験中にコーキングが生じたり、脱AlによりPtに粒成長が生じ、浄化性能の大幅な低下が生じたと考えられる。
【０１６０】
【発明の効果】
すなわち本発明の排ガス浄化方法及び排ガス浄化用触媒によれば、酸素過剰の排ガス中のNO_x を効率よく浄化することができ、かつNO_x 浄化性能の耐久性にきわめて優れているため長期間安定してNO_x を浄化することが可能となる。
【０１６１】
そして運転開始直後あるいは減速時など排ガス温度が低い場合においてもHC及びNO_x を効率よく除去することができ、ディーゼルエンジンの排ガスなど SOFを多く含む排ガス中のNO_x を一層効率よく還元除去することができる。
【０１６２】
したがって本発明は、自動車の排ガス浄化システムに用いることで、NO_x の排出を抑制することができ、自動車排ガスによる大気汚染を抑制することができる。
【図面の簡単な説明】
【図１】浄化率を測定する際のエンジンの運転条件を示すグラフである。
【図２】実施例１〜12及び比較例１〜６の排ガス浄化用触媒の耐久試験後のNO浄化率とHC浄化率を示す棒グラフである。
【図３】参考例１〜10の排ガス浄化用触媒の耐久試験後のNO浄化率とHC浄化率を示す棒グラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification method and an exhaust gas purification catalyst. In this method and catalyst, in the case where oxygen is contained in excess of the amount necessary to oxidize carbon monoxide (CO) or hydrocarbon (HC) contained in the exhaust gas, the nitrogen oxide in the exhaust gas is contained. (NO _x It is suitable when purifying).
[0002]
[Prior art]
CO and HC oxidation and NO as catalysts for automobile exhaust gas purification _x A three-way catalyst that purifies exhaust gas by simultaneously performing reduction of the catalyst is used. As such a catalyst, for example, a porous support layer made of γ-alumina is formed on a heat-resistant support base material such as cordierite, and a noble metal such as Pt, Pd, Rh is supported on this support layer. Widely known.
[0003]
By the way, the purification performance of such an exhaust gas purification catalyst varies greatly depending on the air-fuel ratio (A / F) of the engine. That is, on the lean side where the air-fuel ratio is large, that is, the fuel concentration is lean, the amount of oxygen in the exhaust gas increases, and while the oxidation reaction that purifies CO and HC is active, NO _x The reduction reaction that purifies the water becomes inactive. Conversely, on the rich side where the air-fuel ratio is small, that is, the fuel concentration is high, the amount of oxygen in the exhaust gas decreases and the oxidation reaction becomes inactive, but the reduction reaction becomes active.
[0004]
On the other hand, in the traveling of an automobile, acceleration / deceleration is frequently performed when traveling in an urban area, and the air-fuel ratio frequently changes within the range from the vicinity of stoichiometric (theoretical air-fuel ratio) to the rich state. In order to meet such a demand for lower fuel consumption in traveling, lean burn control for supplying an air-fuel mixture with excess oxygen as much as possible is required. However, the amount of oxygen in the exhaust gas from the lean burn engine is high, and NO _x Reduction reaction to purify is inactive. Therefore, NO in exhaust gas with high oxygen content from lean burn engine _x Development of an exhaust gas purifying catalyst capable of sufficiently purifying gas is desired.
[0005]
For this reason, conventionally, an exhaust gas purifying catalyst employing a zeolite such as mordenite having HC adsorption ability as a catalyst supporting layer has been proposed (for example, JP 04-118030 A). In this exhaust gas purifying catalyst, HC in the exhaust gas is adsorbed while the temperature of the exhaust gas is low, and the adsorbed HC is released when the temperature of the exhaust gas rises. _x NO _x The purification rate can be improved.
[0006]
Zeolite has many acid sites and is acidic, so it has excellent HC adsorption capacity and adsorbs HC in exhaust gas. Therefore, even in the case of exhaust gas in an oxygen-excess atmosphere, the vicinity of the catalyst becomes a stoichiometric to rich atmosphere with a lot of HC, and NO is supported by the catalytic action of the supported noble metal. _x Reacts with adsorbed HC and is reduced and purified.
[0007]
Furthermore, zeolite has a cracking action, and zeolites such as mordenite, ZSM-5, and ultra-stable Y-type zeolite (US-Y) show a particularly high cracking action. Therefore, by using these zeolites as catalyst supports, the SOF in diesel exhaust gas is cracked and becomes a low-molecular HC that is more easily reacted. _x Can be reduced and purified more efficiently.
[0008]
For example, Japanese Patent Laid-Open No. 06-165918 proposes an exhaust gas purification method in which a specific catalyst is provided and liquid HC having 5 or more carbon atoms is added upstream thereof. In this method, HC is supplied from the upstream side while the downstream catalyst is in a low active state, and this HC causes NO. _x NO _x It is intended to improve the purification rate. Here, HC having 5 or more carbon atoms, that is, high-grade HC, is gradually cracked by heat in the exhaust gas, so when the downstream catalyst becomes active at 300 to 500 ° C., the number of carbon atoms is reduced by cracking. Lower HC than 5 and NO _x It is thought that can be reliably reduced.
[0009]
Zeolite is chemically tectoaluminosilicate, and zeolites having various Si / Al ratios are known. It has been found that the catalytic properties of the zeolite vary greatly depending on the value of the Si / Al ratio.
[0010]
Zeolite with a small Si / Al ratio has many acid sites, and shows high cracking ability and high HC adsorption ability. _x Excellent purifying ability. However, in zeolites with a small Si / Al ratio and a large acid point, HC such as soluble organic components (SOF) adsorbed in the pores carbonizes easily and caulks, and as a result, the inside of the pores is blocked. There is a problem that it decreases over time.
[0011]
In addition, zeolites with a small Si / Al ratio and a large number of acid points can easily lose acid sites due to removal of Al (four-coordinate in the zeolite structure becomes six-coordinated) and reduce cracking ability when hydrothermal durability is applied. There is a problem of doing. Furthermore, such a catalyst in which a noble metal is supported on a zeolite has a problem that the activity of the noble metal is reduced due to grain growth due to de-Al removal by hydrothermal durability.
[0012]
On the other hand, zeolite with a large Si / Al ratio has a low cracking ability due to its low acid point. However, since coking does not occur, the HC adsorption capacity does not deteriorate with time, and the grain growth of noble metal due to de-Al is suppressed, so that there is an advantage of excellent durability.
[0013]
[Patent Document 1]
JP 04-118030 A
[Patent Document 2]
JP 06-165918
[0014]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and even exhaust gas containing a large amount of SOF, such as exhaust gas from a diesel engine, is NO. _x It aims at removing more efficiently. Another object of the present invention is to suppress a decrease in HC adsorption capacity using a zeolite having a large Si / Al ratio and to ensure a high cracking ability similar to that of a zeolite having a small Si / Al ratio. _x It aims at removing more efficiently.
[0015]
[Means for Solving the Problems]
A feature of the exhaust gas purification method of the present invention is an exhaust gas purification method for reducing and purifying nitrogen oxides in exhaust gas in an oxygen-excess atmosphere.
A HC adsorbing layer comprising a HC adsorbing material made of zeolite selected from mordenite, ZSM-5 and Y-type zeolite, and a noble metal and a solid superacid supported on the supporting layer, the supporting layer for aluminum The noble metal is composed of zeolite that is super-strongly oxidized with a silicon molar ratio (Si / Al) of 150 or more, a porous carrier, and an oxygen release material that releases oxygen in a rich atmosphere. Not supported on zeolite Using an exhaust gas purifying catalyst supported on at least one of a porous carrier and an oxygen release material,
HC is adsorbed and held by the HC adsorbent, HC released from the HC adsorbent is cracked by a solid superacid, and nitrogen oxides in the exhaust gas are reduced and purified using HC generated thereby as a reducing agent.
[0016]
Further, the exhaust gas purification catalyst of the present invention is characterized in that the exhaust gas purification catalyst for reducing and purifying nitrogen oxides in the exhaust gas in an oxygen-excess atmosphere,
A supporting layer containing an HC adsorbent made of zeolite selected from mordenite, ZSM-5 and Y-type zeolite having HC adsorbing ability, a noble metal and a solid super strong acid supported on the supporting layer, and the supporting layer is silicon against aluminum The noble metal is composed of zeolite that is super-strongly oxidized with a molar ratio (Si / Al) of 150 or more, a porous carrier and an oxygen release material that releases oxygen in a rich atmosphere. Not supported on zeolite It exists in being carry | supported by at least one of a porous support | carrier and an oxygen releasing material.
[0017]
It is desirable that the zeolite has a coating layer made of at least one of titania, silica and zirconia, and the coating layer is super strongly oxidized.
[0018]
The oxygen release material is preferably made of a ceria-zirconia composite oxide having a molar ratio Zr / Ce of 1 or less, and preferably has a coating layer made of at least one of titania, silica, and zirconia. It is desirable that
[0019]
Further, it is desirable that the porous carrier is obtained by super-oxidizing at least one selected from titania, silica, zirconia and alumina coated with at least one of titania, silica and zirconia.
[0020]
The support layer is at least one NO selected from the group consisting of Ir, Pd, Rh, In, Mn and Fe. _x It is preferable that an oxidizing agent is supported, and further NO. _x An occlusion material is preferably included.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
That is, in the exhaust gas purification method of the present invention, HC is cracked by a dehydrogenation reaction with a solid superacid supported on a catalyst support layer, and thereby NO. _x Produces low-reactivity HC with high reactivity. This lower HC is definitely NO _x Reacts with high NO _x An improvement in purification rate is obtained.
[0022]
At this time, since cracking of HC occurs in the catalyst, even when the HC is cracked on the upstream side of the catalyst, even lower HC that is difficult to be adsorbed by the noble metal is easily adsorbed by the noble metal in the present invention. In addition, since HC in exhaust gas or supplied HC is adsorbed and held by the HC adsorbent, the residence time of HC in the catalyst becomes long, and cracking by solid super strong acid, and therefore low HC NO. _x The reactivity with is improved.
[0023]
Furthermore, since HC adsorption by the HC adsorbent is performed in a temperature range where HC is not oxidized, HC emission in the low temperature range is suppressed, and in the high temperature range due to temperature rise, the HC is released from the HC adsorbent. , Cracking of HC by solid super strong acid, and therefore lower HC and NO _x It is utilized for the reaction.
[0024]
Therefore, according to the exhaust gas purification method of the present invention, even if the exhaust gas is in an oxygen-excess atmosphere, the NO _x A purification rate can be exhibited.
[0025]
In the exhaust gas purifying catalyst of the present invention, a heat-resistant honeycomb body made of cordierite or the like can be used as a base material. In this case, it is possible to form a support layer containing the HC adsorbent on the honeycomb body and to support a noble metal on the support layer. Further, the HC adsorbent itself may be formed in a honeycomb shape or a pellet shape, and a noble metal may be supported on the HC adsorbent material.
[0026]
For the support layer, a porous carrier such as alumina, silica, zirconia, titania, silica-alumina or the like can be used. Although this supporting layer contains the HC adsorbing material, the supporting layer can be constituted only by the HC adsorbing material.
[0027]
As the HC adsorbent, a zeolite selected from mordenite, ZSM-5, and Y-type zeolite can be employed.
[0028]
In addition, when other porous carriers are used in combination with zeolite, the content of zeolite is preferably 20% by weight or more. When the content of zeolite is less than 20% by weight, the HC adsorption capacity is reduced, and the effect of the present invention is hardly achieved.
[0029]
The noble metals are gold, silver and platinum group (Ru, Rh, Pd, Os, Ir, Pt). As a practical noble metal, one or more of Pt, Rh and Pd can be adopted. The amount of the precious metal supported on the entire catalyst is suitably in the range of 0.5 to 10 g per liter of the catalyst. If it is less than this range, almost no activity is obtained, and if it is supported more than this, the activity is saturated and the cost increases.
[0030]
Solid strong asid (solid acid substance) is a solid acid obtained by treating oxides such as zirconia, alumina and titania with strong acids such as sulfuric acid, tungstic acid and molybdic acid, and attaching strong acids to the oxides. Can be adopted. The solid superacid is prepared by adsorbing an aqueous solution of a water-soluble metal salt to the support layer and then treating the water-soluble metal salt with an alkali to expose the metal hydroxide to the support layer. It is desirable to treat and carry on the carrying layer. In this way, since the solid superacid can be chemically supported on the support layer, fine solid superacid diffuses uniformly around the pores of the HC adsorbent. For this reason, HC is surely in contact with the solid super strong acid and easily cracked.
[0031]
Solid superacids are defined as acidity function (hammet acid strength) Ho <-11.0 to -11.9.
[0032]
It is more preferable to employ a cerium sulfate / zirconium composite oxide as the solid superacid. The cerium sulfate / zirconium composite oxide may be a Ce-Zr-Y composite oxide, a Ce-Zr-Ca composite oxide, or the like. The ceria-based oxide has an oxygen storage capability of releasing oxygen when rich and storing oxygen when lean. The ceria-based solid superacid is a ceria-based oxide converted into an acidic carrier and also has an oxygen storage capacity. For this reason, in the first catalyst that employs a cerium sulfate-zirconium composite oxide as the solid superacid, the oxygen released by the ceria-based solid superacid will convert NO in the exhaust gas to NO. ₂ It is oxidized to make it easy to adsorb to the precious metal of the catalyst. Because of this, NO _x Is efficiently reduced and purified by low-grade HC that is concentrated on precious metals and cracked.
[0033]
In addition, sulfur (S) contained in the fuel is burned and generated in the exhaust gas. ₂ It is further oxidized by precious metals in an oxygen-rich atmosphere and SO _Three It becomes. In other words, these sulfates are also included in the exhaust gas. For this reason, in the catalyst containing a ceria-based oxide, there is a problem that sulfate is easily adsorbed on the ceria-based oxide, and the oxygen storage capacity is reduced. However, a catalyst that uses cerium sulfate / zirconium composite oxide as a solid super strong acid is difficult to adsorb sulfate due to the acid nature of cerium sulfate / zirconium composite oxide, and oxygen storage capacity of cerium sulfate / zirconium composite oxide. Is not reduced.
[0034]
In the exhaust gas purifying catalyst of the present invention, the support layer is composed of a super-oxidized zeolite having a silicon-to-aluminum molar ratio (Si / Al) of 150 or more, a porous carrier and an oxygen release material, and the noble metal is porous. It is carried on at least one of the carrier and the oxygen release material. By setting the Si / Al ratio of the zeolite to 150 or higher, almost no de-Al is generated, so that a decrease in HC adsorption capacity over time is prevented. Moreover, since there are few acid points, coking is also suppressed.
[0035]
However, zeolites with a Si / Al ratio of 150 or more have low acid sites, so cracking ability is low, and SOF cracking becomes insufficient, resulting in NO by HC. _x There is a problem that the reduction and purification of the water becomes insufficient. Therefore, in the present invention, zeolite is used after being superoxidized. The characteristic of cracking SOF is ensured by super strong oxidation, and NO is generated by HC generated by cracking. _x The reductive purification rate is significantly improved.
[0036]
On the other hand, when a noble metal is supported on zeolite, the adsorption heat of HC to the zeolite is inhibited by the reaction heat of the oxidation reaction of HC. In addition, the noble metal supported in the pores of the zeolite has a reduced active site due to pore clogging caused by coking.
[0037]
Therefore, it is desirable that the noble metal is not supported on zeolite but is supported on at least one of a porous carrier and an oxygen release material. This facilitates the adsorption of HC to the zeolite and also suppresses the decrease in precious metal activity. _x Purifying ability is improved.
[0038]
The porous carrier is mainly used for the purpose of supporting a noble metal. The porous carrier is preferably selected from at least one of titania, zirconia and silica. Alumina is SO _x It is not preferable because it is easy to adsorb, and the activity may decrease due to sulfur poisoning.
[0039]
Further, since noble metal adsorbs not only NO but also oxygen present in the atmosphere, oxygen poisoning occurs in which the surface of the noble metal is covered with oxygen and the activity is reduced. However, it has been clarified that when a noble metal is supported on a porous carrier made of at least one of titania, silica and zirconia, oxygen poisoning is suppressed as compared with the case where it is supported on alumina. Therefore, by supporting a noble metal on a porous carrier made of at least one of titania, silica, and zirconia, a decrease in activity due to oxygen poisoning is suppressed, and high durability is expressed.
[0040]
In addition, it is also preferable that the porous carrier has a configuration in which alumina is coated with at least one of titania, zirconia, and silica, and a noble metal is supported on the coating layer. In this way, since an oxide layer having high acidity is formed on the outermost surface, it is possible to prevent the sulfur oxide in the exhaust gas from coming close to the noble metal on which the sulfur oxide is poisoned. It is suppressed. In addition, the influence of alumina having a high specific surface area is greatly manifested, and noble metal grain growth is also suppressed.
[0041]
Furthermore, it is also preferable to super strongly oxidize at least one coat layer of titania, zirconia and silica formed on the alumina surface. In this way, since the acidity of the surface is further enhanced, sulfur poisoning is further suppressed. Further, by using a super strong oxide layer, oxygen poisoning of noble metals is further suppressed. Therefore, by adopting a structure in which a noble metal is supported on the outermost superoxide oxide layer, NO _x The durability of the purification activity is further improved.
[0042]
The oxygen release material brings the catalyst surface that has become rich due to the release of HC from the zeolite closer to the stoichiometry due to the release of oxygen. ₂ NO by promoting oxidation to HC and facilitating reaction with HC _x Has the function of improving the purification capacity.
[0043]
Therefore, if the noble metal is supported on the surface of the oxygen release material, the above action is performed smoothly, and NO _x Purifying ability is further improved. Moreover, the effect | action that an oxygen release rate improves by carrying | supporting a noble metal is also show | played.
[0044]
As this oxygen release material, ceria can be used. It is also preferable to use ceria stabilized by dissolving zirconia in a solid solution. In this case, the composition ratio of the ceria-zirconia composite oxide is not particularly limited, but those having a molar ratio of Zr / Ce ≦ 1 have high oxygen releasing ability but are easily sulfur poisoned. When Zr / Ce> 1, the sulfur poisoning Is resistant but has a low oxygen release capacity.
[0045]
Therefore, it is preferable to form a coating layer made of at least one of titania, zirconia and silica on the surface of the ceria-zirconia composite oxide with Zr / Ce ≦ 1. In this way, sulfur poisoning can be suppressed while ensuring high oxygen releasing ability. Further, if the coating layer is further superoxidized, the oxygen releasing material can also exhibit a cracking action.
[0046]
In order to obtain a super-strongly oxidized zeolite, the zeolite may be super-strongly oxidized directly, but the surface of the zeolite having a Si / Al ratio of 150 or more is made of at least one of titania, zirconia and silica and is super-strong by acid treatment. It is desirable to form an oxidized super strong oxide layer. If a noble metal is supported on the super strong acid oxide layer formed on the zeolite surface, when HC adsorbed on the zeolite is released, it is surely NO on the noble metal. _x HC and NO that react with HC and have been reduced in molecular weight by cracking _x Because the probability of reaction with increases, NO _x The purification rate is further improved.
[0047]
The super strong acid oxide layer can be formed by forming an oxide layer made of at least one of titania, zirconia, and silica on the zeolite surface, and subjecting it to a super strong acid treatment. In order to form the oxide layer, for example, the zeolite is dispersed in an aqueous nitrate solution of at least one of titanium, zirconium, and silicon, and an aqueous ammonia solution is dropped and coprecipitated, followed by filtration, drying, and firing. be able to. The super strong acid treatment can be performed by treating a zeolite having an oxide layer with a super strong acid aqueous solution such as sulfuric acid, molybdic acid, and tungstic acid, filtering, drying, and firing.
[0048]
This super strong oxide layer is preferably formed such that the zeolite is 10 to 20 with respect to the super strong oxide 1 by weight. If the amount of the super strong acid oxide is less than this range, the effect of forming the super strong oxide layer cannot be obtained, and if it exceeds this range, the pores of the zeolite are blocked, so that the HC adsorption capacity decreases and the NO is reduced. _x The purification activity is also reduced.
[0049]
The noble metal may be supported on either the zeolite or the super strong oxide layer, but is preferably supported on the super strong oxide layer. As a result, HC and NO are reduced in molecular weight by cracking. _x Increase the probability of reaction with NO _x The purification rate is further improved.
[0050]
It is also preferable to use a noble metal supported on an oxide such as silica, titania or zirconia and mixed with a zeolite having a super strong oxide layer. In this way, compared with the case where the noble metal is supported on the super strong oxide layer, the NO in the exhaust gas is easily adsorbed by the noble metal, and the NO released by the HC released through the super strong oxide layer. _x Can be more reliably reduced and purified. In this case, it is not preferable to use alumina as a noble metal support. Because alumina is SO _x It is because it is easy to adsorb | suck and activity may fall by sulfur poisoning.
[0051]
That is, in the exhaust gas purifying catalyst of the present invention, the use of zeolite having a Si / Al ratio of 150 or more suppresses a decrease in HC adsorption capacity over time, and sufficient cracking can be achieved by forming a super strong oxide layer on the surface. Performance is secured. Therefore, SOF in the exhaust gas is cracked by the super strong oxide layer, and the produced HC and the HC in the exhaust gas are adsorbed by the zeolite.
[0052]
On the other hand, NO in exhaust gas _x Is partially oxidized by oxygen present in the exhaust gas on the surface of the noble metal, but reacts with HC released from the zeolite on the surface of the noble metal to react with N. ₂ It is reduced and purified.
[0053]
The support layer is at least one NO selected from the group consisting of Ir, Pd, Rh, In, Mn and Fe. _x It is desirable that an oxidizing agent is supported. NO like this _x By supporting an oxidizer, NO → NO ₂ This reaction is promoted and is easily adsorbed on the noble metal of the catalyst. NO for this _x Is concentrated in the vicinity of noble metals and efficiently reduced by lower HC formed by cracking. _x The purification rate is further improved. The supported Mn and Fe become oxides by firing in the catalyst generation step.
[0054]
This NO _x The amount of the oxidant supported is suitably in the range of 0.01 to 1.5 mol per liter of catalyst. If the loading amount is less than this range, the above effect is not achieved. _x Reduction reaction is inhibited and NO _x The purification rate decreases.
[0055]
In addition, the carrier layer further contains NO. _x It is desirable to include an occlusion material. NO → NO with oxygen release material ₂ NO produced by promoting the reaction of _x NO _x By storing in the storage material, NO in an oxygen-excessive atmosphere _x Emission is suppressed. And NO _x NO released from occlusion material _x Reacts with HC released from the HC adsorbent and is reduced. Therefore NO _x NO is absorbed and reduced. _x The purification rate is further improved. Furthermore, since the SOF adsorbed on the catalyst is oxidized by the oxygen released from the oxygen release material, the SOF desorption is promoted.
[0056]
The type of oxygen releasing material used can be the same as described above. NO _x The occlusion material refers to an oxide or carbonate of a metal selected from alkali metals, alkaline earth metals and rare earth elements, and can be contained in a range of 0.01 to 1.0 mol with respect to 1 liter of catalyst.
[0057]
【Example】
Table 1 summarizes the compositions of the catalysts of the examples and comparative examples described below.
[0058]
[Table 1]

[0059]
Example 1
<Zeolite>
1000 parts of commercially available mordenite powder (“HSZ690HOA” manufactured by Tosoh Corporation, Si / Al ratio = 200) was prepared, mixed with an aqueous solution in which 145 parts of zirconium oxynitrate was dissolved in 5000 parts of pure water, and stirred for 30 minutes. Thereafter, 200 parts of a 25% aqueous ammonia solution was mixed, and further mixed for 30 minutes. After aging for 12 hours, it was filtered, washed with water, and dried in air at 110 ° C. for 2 hours.
[0060]
The total amount of the obtained powder was mixed in 5000 parts of a 1N aqueous sulfuric acid solution, stirred for 1 hour, filtered, dried in air at 110 ° C. for 2 hours, and further calcined in air at 700 ° C. for 3 hours. Thereby, the super strong zirconia layer was formed on the surface of the mordenite powder.
[0061]
<Porous carrier>
100 parts of titania powder, 100 parts of a 4% by weight hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. Subsequently, heating is continued at 100 ° C to evaporate the water to dryness, followed by drying at 120 ° C for 2 hours and then firing at 300 ° C for 2 hours to obtain Pt-supported titania (Pt / TiO 2 ₂ ) A powder was prepared. The supported amount of supported Pt is 2% by weight.
[0062]
<Oxygen releasing material>
100 parts of ceria-zirconia composite oxide (Zr / Ce = 1/4) powder, 100 parts of a 4% by weight hexaammineplatinum hydrochloride aqueous solution and 200 parts of pure water were mixed and stirred for 1 hour. Thereafter, heating was continued at 100 ° C. to evaporate and dry the water, followed by drying at 120 ° C. for 2 hours and further baking at 300 ° C. for 2 hours to prepare Pt-supported CZS (Pt / CZS) powder. The supported amount of supported Pt is 2% by weight.
[0063]
<Coating>
90 parts of mordenite powder with super strong zirconia layer and Pt / TiO ₂ 60 parts of powder, 30 parts of Pt / CZS powder, 200 parts of pure water and 55 parts of titania sol (solid content 35%) were mixed and stirred to prepare a slurry. And cordierite honeycomb carrier substrate (400 cells / in ² , Volume 1.7 L) was prepared, dipped in the slurry and pulled up to blow off excess slurry, dried at 100 ° C. for 2 hours, and calcined at 500 ° C. for 2 hours to obtain the catalyst of Example 1. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0064]
(Example 2)
<Zeolite>
The same as in the first embodiment.
[0065]
<Porous carrier>
Pt-supported silica (Pt / SiO) in the same manner as in Example 1 except that 100 parts of silica powder was used instead of titania powder. ₂ ) A powder was prepared.
[0066]
<Oxygen releasing material>
The same as in the first embodiment.
[0067]
<Coating>
Pt / SiO instead of Pt-supported titania powder ₂ A catalyst of Example 2 was prepared in the same manner as in Example 1 except that 60 parts of powder was used and 55 parts of silica sol (solid content 35%) was used instead of titania sol. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0068]
Example 3
<Zeolite>
The same as in the first embodiment.
[0069]
<Porous carrier>
Pt-supported zirconia (Pt / ZrO) was carried out in the same manner as in Example 1 except that 100 parts of zirconia powder was used instead of titania powder. ₂ ) A powder was prepared.
[0070]
<Oxygen releasing material>
The same as in the first embodiment.
[0071]
<Coating>
Pt / ZrO instead of Pt-supported titania powder ₂ A catalyst of Example 3 was prepared in the same manner as Example 1 except that 60 parts of the powder was used and 55 parts of zirconia sol (solid content 35%) was used instead of the titania sol. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0072]
Example 4
<Zeolite>
The surface of the Y-type zeolite powder was super strong in the same manner as in Example 1 except that the same amount of Y-type zeolite powder (“HSZ390HUA” manufactured by Tosoh Corporation, Si / Al ratio = 400) was used instead of the mordenite powder. A zirconia oxide layer was formed.
[0073]
<Porous carrier>
The same as in the first embodiment.
[0074]
<Oxygen releasing material>
The same as in the first embodiment.
[0075]
<Coating>
A catalyst of Example 4 was prepared in the same manner as in Example 1 except that 90 parts of Y-type zeolite powder having a super strong zirconia layer was used instead of the mordenite powder having a super strong zirconia layer. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0076]
(Example 5)
<Zeolite>
ZSM-5 type zeolite powder was used in the same manner as in Example 1 except that ZSM-5 type zeolite powder (“HSZ890HOA” manufactured by Tosoh Corporation, Si / Al ratio = 2000) was used instead of mordenite powder. A super strong zirconia layer was formed on the surface.
[0077]
<Porous carrier>
The same as in the first embodiment.
[0078]
<Oxygen releasing material>
The same as in the first embodiment.
[0079]
<Coating>
A catalyst of Example 5 was prepared in the same manner as Example 1 except that 90 parts of ZSM-5 type zeolite powder having a super strong zirconia layer was used instead of the mordenite powder having a super strong zirconia layer. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0080]
(Example 6)
<Zeolite>
The same as in the first embodiment.
[0081]
<Porous carrier>
The same as in the first embodiment.
[0082]
<Oxygen releasing material>
500 parts of ceria-zirconia composite oxide (Zr / Ce = 1/4) powder was mixed with an aqueous solution in which 300 parts of zirconium oxynitrate was dissolved in 2000 parts of pure water and stirred for 30 minutes. Thereafter, 300 parts of a 25% aqueous ammonia solution was mixed and further mixed for 30 minutes. After aging for 12 hours, it was filtered, washed with water, and dried in air at 110 ° C. for 2 hours. Thereafter, it was calcined in the atmosphere at 500 ° C. for 3 hours to prepare CZS (Zr-CZS) powder having a zirconia layer.
[0083]
Next, 100 parts of Zr-CZS powder, 100 parts of a 4 wt% hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. Subsequently, heating was continued at 100 ° C. to evaporate and dry the water, followed by drying at 120 ° C. for 2 hours and further baking at 300 ° C. for 2 hours to prepare Pt-supported Zr-CZS (Pt / Zr-CZS) powder. The supported amount of supported Pt is 2% by weight.
[0084]
<Coating>
90 parts of mordenite powder having a super-strong oxide zirconia layer similar to that in Example 1, and Pt / TiO as in Example 3. ₂ 60 parts of powder, 30 parts of Pt / Zr-CZS powder, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. Then, the same honeycomb carrier base material as in Example 1 was prepared and coated in the same manner as in Example 1 to obtain the catalyst of Example 6. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0085]
(Example 7)
<Zeolite>
The same as in the first embodiment.
[0086]
<Porous carrier>
The same as in the third embodiment.
[0087]
<Oxygen releasing material>
500 parts of ceria-zirconia composite oxide (Zr / Ce = 1/4) powder was mixed with an aqueous solution in which 300 parts of zirconium oxynitrate was dissolved in 2000 parts of pure water and stirred for 30 minutes. Thereafter, 300 parts of a 25% aqueous ammonia solution was mixed and further mixed for 30 minutes. After aging for 12 hours, it was filtered, washed with water, and dried in air at 110 ° C. for 2 hours.
[0088]
Next, the total amount of the obtained Zr-CZS powder was mixed with 5000 parts of 1N sulfuric acid aqueous solution, stirred for 1 hour, filtered and dried in air at 110 ° C for 2 hours, and further in air at 700 ° C. Super strong oxidation Zr-CZS powder was prepared by firing for 3 hours.
[0089]
Next, 100 parts of super strong oxidized Zr-CZS powder, 100 parts of a 4 wt% hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. After that, it is continuously heated at 100 ° C to evaporate and dry the water, dried at 120 ° C for 2 hours, then calcined at 300 ° C for 2 hours, and then Pt-supported super strong oxide Zr-CZS (Pt / super strong oxide Zr-CZS) powder Was prepared. The supported amount of supported Pt is 2% by weight.
[0090]
<Coating>
90 parts of a mordenite powder with a super-strong oxide zirconia layer as in Example 1 and Pt / ZrO as in Example 3 ₂ 60 parts of powder, 30 parts of Pt / super strong oxidation Zr-CZS powder, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. Then, the same honeycomb carrier base material as in Example 1 was prepared and coated in the same manner as in Example 1 to obtain the catalyst of Example 7. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0091]
(Example 8)
<Zeolite>
The same as in the first embodiment.
[0092]
<Porous carrier>
Activated alumina (specific surface area 200m ² / G) 500 parts of powder was mixed with an aqueous solution in which 300 parts of zirconium oxynitrate was dissolved in 2000 parts of pure water and stirred for 30 minutes. Thereafter, 300 parts of a 25% aqueous ammonia solution was mixed and further mixed for 30 minutes. After aging for 12 hours, it was filtered, washed with water, and dried in air at 110 ° C. for 2 hours. After that, it was calcined in the atmosphere at 500 ° C for 3 hours, and alumina with a zirconia layer (Zr-Al ₂ O _Three ) A powder was prepared.
[0093]
Next, Zr-Al ₂ O _Three 100 parts of powder, 100 parts of a 4% by weight hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. Then, heating is continued at 100 ° C to evaporate and dry the water, dried at 120 ° C for 2 hours, and then fired at 300 ° C for 2 hours to obtain Pt-supported Zr-alumina (Pt / Zr-Al ₂ O _Three ) A powder was prepared. The supported amount of supported Pt is 2% by weight.
[0094]
<Oxygen releasing material>
The same as in the first embodiment.
[0095]
<Coating>
90 parts of mordenite powder having the same super-strong oxide zirconia layer as in Example 1, and the above Pt / Zr—Al ₂ O _Three 60 parts of powder, 30 parts of the same Pt / CZS powder as in Example 1, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. Then, the same honeycomb carrier base material as in Example 1 was prepared and coated in the same manner as in Example 1 to obtain the catalyst of Example 8. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0096]
Example 9
<Zeolite>
The same as in the first embodiment.
[0097]
<Porous carrier>
Activated alumina (specific surface area 200m ² / G) 500 parts of powder was mixed with an aqueous solution in which 300 parts of zirconium oxynitrate was dissolved in 2000 parts of pure water and stirred for 30 minutes. Thereafter, 300 parts of a 25% aqueous ammonia solution was mixed and further mixed for 30 minutes. After aging for 12 hours, it was filtered, washed with water, and dried in air at 110 ° C. for 2 hours.
[0098]
Next, the obtained Zr-Al ₂ O _Three The total amount of the powder is mixed with 5000 parts of 1N sulfuric acid aqueous solution and stirred for 1 hour. After filtration, it is dried in air at 110 ° C for 2 hours, and further calcined in air at 700 ° C for 3 hours to super strong oxidation. Zirconia layer forming alumina (super strong oxide Zr-Al ₂ O _Three ) A powder was prepared.
[0099]
Next, super strong oxidation Zr-Al ₂ O _Three 100 parts of powder, 100 parts of a 4% by weight hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. After that, it was continuously heated at 100 ° C to evaporate and dry the water, dried at 120 ° C for 2 hours, and then calcined at 300 ° C for 2 hours to obtain Pt-supported super strong oxide Zr-alumina powder (Pt / super strong oxide Zr-Al ₂ O _Three ) Was prepared. The supported amount of supported Pt is 2% by weight.
[0100]
<Oxygen releasing material>
The same as in the first embodiment.
[0101]
<Coating>
90 parts of mordenite powder having the same super-strong oxide zirconia layer as in Example 1, and the above-mentioned Pt / super-strong oxide Zr—Al ₂ O _Three 60 parts of powder, 30 parts of the same Pt / CZS powder as in Example 1, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier base material similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Example 9. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0102]
(Example 10)
<Zeolite>
The same as in the first embodiment.
[0103]
<Porous carrier>
Activated alumina (specific surface area 200m ² / G) 500 parts of the powder was mixed with 3000 parts of 1N aqueous sulfuric acid solution, stirred for 3 hours, filtered, and dried in the atmosphere at 110 ° C. for 2 hours. After that, it was calcined in the atmosphere at 700 ° C for 3 hours, and super strong alumina (super strong oxide Al). ₂ O _Three ) A powder was prepared.
[0104]
Next, super strong oxidation Al ₂ O _Three 100 parts of powder, 100 parts of a 4% by weight hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. After that, it is continuously heated at 100 ° C to evaporate and dry the water, dried at 120 ° C for 2 hours, and then calcined at 300 ° C for 2 hours to burn Pt-supported super strong oxide (Pt / super strong oxide Al). ₂ O _Three ) A powder was prepared. The supported amount of supported Pt is 2% by weight.
[0105]
<Oxygen releasing material>
The same as in the first embodiment.
[0106]
<Coating>
90 parts of mordenite powder having the same super-strong oxide zirconia layer as in Example 1 and the above Pt / super-strong oxide Al ₂ O _Three 60 parts of powder, 30 parts of the same Pt / CZS powder as in Example 1, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier substrate similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Example 10. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0107]
(Example 11)
100 parts of titania powder, 100 parts of a 6% by weight hexaammine platinum hydroxide aqueous solution and 200 parts of pure water were mixed and stirred for 1 hour. Subsequently, heating is continued at 100 ° C to evaporate the water to dryness, followed by drying at 120 ° C for 2 hours, and further baking at 300 ° C for 2 hours to obtain Pt-supported titania () Pt / TiO ₂ A powder was prepared. The supported amount of supported Pt is 3% by weight.
[0108]
90 parts of mordenite powder having the same super-strong oxide zirconia layer as in Example 1, and the resulting Pt / TiO ₂ 60 parts of powder, 30 parts of ceria-zirconia composite oxide (CZS, Zr / Ce = 1/4) powder, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) are mixed and stirred. A slurry was prepared. Then, the same honeycomb carrier base material as in Example 1 was prepared and coated in the same manner as in Example 1 to obtain the catalyst of Example 11. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0109]
(Example 12)
Activated alumina (specific surface area 200m ² / G) 100 parts of powder, 100 parts of a 4% by weight hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. Then continue to heat at 100 ° C to evaporate the water to dryness, dry at 120 ° C for 2 hours and then fire at 300 ° C for 2 hours to Pt / Al ₂ O _Three A powder was prepared. The supported amount of supported Pt is 2% by weight.
[0110]
90 parts of mordenite powder having the same super-strong oxide zirconia layer as in Example 1 and the obtained Pt / Al ₂ O _Three 60 parts of powder, 30 parts of the same Pt / CZS powder as in Example 1, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier substrate similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Example 12. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0111]
(Comparative Example 1)
90 parts of commercially available mordenite powder (“HSZ690HOA” manufactured by Tosoh Corporation, Si / Al ratio = 200) and Pt / TiO as in Example 1 ₂ 60 parts of powder, 30 parts of the same Pt / CZS powder as in Example 1, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier substrate similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Comparative Example 1. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0112]
(Comparative Example 2)
1000 parts of commercially available mordenite powder (“HSZ660HOA” manufactured by Tosoh Corporation, Si / Al ratio = 30) was prepared, mixed with an aqueous solution in which 145 parts of zirconium oxynitrate was dissolved in 5000 parts of pure water, and stirred for 30 minutes. Thereafter, 200 parts of a 25% aqueous ammonia solution was mixed, and further mixed for 30 minutes. After aging for 12 hours, it was filtered, washed with water, and dried in air at 110 ° C. for 2 hours.
[0113]
The total amount of the obtained powder was mixed in 5000 parts of a 1N aqueous sulfuric acid solution, stirred for 1 hour, filtered, dried in air at 110 ° C. for 2 hours, and further calcined in air at 700 ° C. for 3 hours. Thereby, the super strong zirconia layer was formed on the surface of the mordenite powder.
[0114]
90 parts of the obtained mordenite powder having a super-strong oxide zirconia layer and Pt / TiO as in Example 1 were obtained. ₂ The final 60 parts, 30 parts of the same Pt / CZS powder as in Example 1, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier base material similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Comparative Example 2. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0115]
(Comparative Example 3)
100 parts of mordenite powder having the same super-strong oxide zirconia layer as in Example 1, 100 parts of a 2% by weight hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. After that, it is continuously heated at 100 ° C to evaporate and dry the water, dried at 120 ° C for 2 hours, and then calcined at 300 ° C for 2 hours to form mordenite with Pt-supported super strong zirconia layer (Pt / super strong oxide ZrO ₂ Layer formation-mordenite) powder was prepared. The supported amount of supported Pt is 1% by weight.
[0116]
Further, 100 parts of titania powder, 100 parts of a 2% by weight hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. After that, it is heated at 100 ° C to evaporate the water, dried at 120 ° C for 2 hours, and then fired at 300 ° C for 2 hours to obtain Pt / TiO ₂ A powder was prepared. The supported amount of supported Pt is 1% by weight.
[0117]
Furthermore, 100 parts of ceria-zirconia composite oxide (Zr / Ce = 1/4) powder, 100 parts of a 2 wt% hexaammineplatinum hydrate solution and 200 parts of pure water were mixed and stirred for 1 hour. Thereafter, the mixture was continuously heated at 100 ° C. to evaporate and dry the water, dried at 120 ° C. for 2 hours, and then calcined at 300 ° C. for 2 hours to prepare Pt / CZS powder. The supported amount of supported Pt is 1% by weight.
[0118]
Pt / Super strong oxidation ZrO ₂ Layer formation-90 parts of mordenite powder and Pt / TiO ₂ 60 parts of powder, 30 parts of Pt / CZS powder, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier base material similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Comparative Example 3. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0119]
(Comparative Example 4)
90 parts of commercially available mordenite powder (“HSZ660HOA” manufactured by Tosoh Corporation, Si / Al ratio = 30) and Pt / TiO as in Example 1 ₂ 60 parts of powder, 30 parts of the same Pt / CZS powder as in Example 1, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier substrate similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Comparative Example 4. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0120]
(Comparative Example 5)
The same Pt / TiO as in Example 1 without using zeolite ₂ 60 parts of powder, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier substrate similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Comparative Example 5. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0121]
(Comparative Example 6)
90 parts of mordenite powder having a super-strong oxide zirconia layer similar to that in Example 1, and Pt / TiO as in Example 1. ₂ 60 parts of powder, 200 parts of pure water and 55 parts of zirconia sol (solid content 35%) were mixed and stirred to prepare a slurry. A honeycomb carrier base material similar to that in Example 1 was prepared and coated in the same manner as in Example 1 to obtain a catalyst of Comparative Example 6. The coating amount is 180 g per liter of the carrier substrate, and the supported amount of Pt is 1.8 g per liter of the carrier substrate.
[0122]
(Evaluation test)
Each of the above-mentioned catalysts is installed in the exhaust system of a 2400cc in-line four-cylinder diesel engine, and the endurance test for 25 hours is carried out by adjusting the gas temperature with catalyst to 600 ° C by the load at a constant speed of 3600 rpm. went.
[0123]
Each catalyst after the endurance test is installed in the same exhaust system of the engine as in the endurance test, and the load is changed so that the number of revolutions changes in the range of 1000-2500 rpm as shown in Fig. 1, and the diesel oil in the exhaust gas While adding 300 to 1200 ppmC, the purification rate of HC and NO was measured respectively. The results are shown in FIG.
[0124]
From FIG. 2, it can be seen that the catalyst of each example has a higher NO purification rate and HC purification rate after durability than the catalyst of the comparative example, and is excellent in durability.
[0125]
When analyzed in more detail, the catalyst of Example 11 has a lower purification rate than Example 1. This difference is attributed to the difference in the presence or absence of Pt on the oxygen release material, and it is understood that it is preferable to carry Pt on the oxygen release material.
[0126]
The catalyst of Example 8 has a lower purification rate than that of Example 1. This difference is due to the difference in the type of porous oxide, and it can be seen that titania is preferable to alumina having a zirconia layer.
[0127]
When Example 3 and Example 7 are compared, the catalyst of Example 7 has a higher purification rate. That is, it is understood that it is preferable to super-oxidize the coating layer of the oxygen release material. Further, it can be seen from the comparison between Example 8 and Example 9 that it is preferable to superoxidize the porous carrier.
[0128]
In Comparative Example 1, the zeolite is not superoxidized, so the purification rate is lower than in Example 1. In Comparative Examples 2 and 4, the purification rate is low because the Si / Al ratio of zeolite is as small as 30. Low. In Comparative Example 3, the purification rate is low because Pt is supported on the zeolite. In Comparative Examples 2 and 4, the purification rate of Comparative Example 2 is higher, but this is due to the difference in the presence or absence of the super strong zirconia layer of zeolite, and super strong zirconia even if the Si / Al ratio is small. It can be seen that forming the layer is preferred.
[0129]
Further, in Comparative Example 5, neither the zeolite nor the oxygen releasing material is present, so that the purification rate is extremely low, and in Comparative Example 6, since no oxygen releasing material is provided, the purification rate is lower than that in Example 1.
[0130]
That is, the difference in these effects is due to the difference in the structure of the support, and NO by making the structure of the catalyst of the present invention. _x It is clear that the durability of the purification ability is improved.
[0131]
(Reference Example 1)
<Formation of super strong oxide layer>
1000 parts of commercially available mordenite powder (“HSZ690HOA” manufactured by Tosoh Corporation, Si / Al ratio = 200) was prepared, mixed with an aqueous solution in which 145 parts of zirconium oxynitrate was dissolved in 5000 parts of pure water, and stirred for 30 minutes. Thereafter, 200 parts of a 25% aqueous ammonia solution was mixed, and further mixed for 30 minutes. After aging for 12 hours, it was filtered, washed with water, and dried in air at 110 ° C. for 2 hours.
[0132]
The total amount of the obtained powder was mixed in 5000 parts of a 1N aqueous sulfuric acid solution, stirred for 1 hour, filtered, dried in air at 110 ° C. for 2 hours, and further calcined in air at 700 ° C. for 3 hours. Thereby, the super strong zirconia layer was formed on the surface of the mordenite powder.
[0133]
<Supporting precious metals>
100 parts of the mordenite powder having the super-strong oxide zirconia layer obtained above, 100 parts of a 1% by weight hexaammineplatinum hydrochloride aqueous solution and 200 parts of pure water were mixed and stirred for 1 hour. Thereafter, heating was continued at 100 ° C. to evaporate and dry the water, followed by drying at 120 ° C. for 2 hours and further baking at 300 ° C. for 2 hours. The supported amount of Pt thus supported is 1% by weight.
[0134]
<Coating>
150 parts of mordenite powder carrying Pt and having a super strong zirconia layer, 200 parts of pure water and 55 parts of silica sol (solid content 35%) were mixed and stirred to prepare a slurry. Then, a cordierite honeycomb carrier base material (volume 1.5 L) was prepared, dipped in the slurry and pulled up to blow off the excess slurry, dried at 100 ° C. for 2 hours, fired at 500 ° C. for 2 hours, and Reference Example 1 The catalyst was obtained. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0135]
(Reference Example 2)
An ultra-strong oxide titania layer was formed on the surface of the mordenite powder in the same manner as in Reference Example 1 except that 145 parts of titanium oxynitrate was used instead of zirconium oxynitrate.
[0136]
Using this mordenite powder having a super strong acid titania layer, a noble metal was supported and coated in the same manner as in Reference Example 1 to prepare a catalyst of Reference Example 2. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0137]
(Reference Example 3)
<Formation of super strong oxide layer>
150 parts of commercially available mordenite powder (“HSZ690HOA” manufactured by Tosoh Corporation, Si / Al ratio = 200) and 33 parts of zirconia sol having a solid content of 30% by weight were mixed and stirred for 30 minutes. Thereafter, heating was continued at 100 ° C. to evaporate and dry the water, followed by drying at 120 ° C. for 2 hours and further baking at 300 ° C. for 2 hours.
[0138]
1000 parts of the obtained powder was mixed in 5000 parts of 1N aqueous sulfuric acid solution, stirred for 1 hour, filtered, dried in air at 110 ° C. for 2 hours, and further calcined in air at 700 ° C. for 3 hours. Thereby, the super strong zirconia layer was formed on the surface of the mordenite powder.
[0139]
Using this mordenite powder having a super-strong oxide zirconia layer, a noble metal was supported and coated in the same manner as in Reference Example 1 to prepare a catalyst of Reference Example 3. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0140]
(Reference Example 4)
<Formation of super strong oxide layer>
150 parts of commercially available mordenite powder (“HSZ690HOA” manufactured by Tosoh Corporation, Si / Al ratio = 200) and 33 parts of titania sol having a solid content of 30% by weight were mixed and stirred for 30 minutes. Thereafter, heating was continued at 100 ° C. to evaporate and dry the water, followed by drying at 120 ° C. for 2 hours and further baking at 300 ° C. for 2 hours.
[0141]
1000 parts of the obtained powder was mixed in 5000 parts of 1N aqueous sulfuric acid solution, stirred for 1 hour, filtered, dried in air at 110 ° C. for 2 hours, and further calcined in air at 700 ° C. for 3 hours. As a result, an ultra-strong oxide titania layer was formed on the surface of the mordenite powder.
[0142]
Using this mordenite powder having a super strong oxide titania layer, a noble metal was supported and coated in the same manner as in Reference Example 1 to prepare a catalyst of Reference Example 4. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0143]
(Reference Example 5)
<Formation of super strong oxide layer>
150 parts of commercially available mordenite powder (“HSZ690HOA” manufactured by Tosoh Corporation, Si / Al ratio = 200) and 33 parts of silica sol having a solid content of 30% by weight were mixed and stirred for 30 minutes. Thereafter, heating was continued at 100 ° C. to evaporate and dry the water, followed by drying at 120 ° C. for 2 hours and further baking at 300 ° C. for 2 hours.
[0144]
1000 parts of the obtained powder was mixed in 5000 parts of 1N aqueous sulfuric acid solution, stirred for 1 hour, filtered, dried in air at 110 ° C. for 2 hours, and further calcined in air at 700 ° C. for 3 hours. As a result, an ultra strong silica layer was formed on the surface of the mordenite powder.
[0145]
Using this mordenite powder having a super strong oxide silica layer, a noble metal was supported and coated in the same manner as in Reference Example 1 to prepare a catalyst of Reference Example 5. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0146]
(Reference Example 6)
Super strong on the surface of the Y-type zeolite powder in the same manner as in Reference Example 1 except that the same amount of Y-type zeolite powder (“HSZ390HUA” manufactured by Tosoh Corporation, Si / Al ratio = 400) was used instead of the mordenite powder. A zirconia oxide layer was formed.
[0147]
Using this Y-type zeolite powder having a super-strong oxide zirconia layer, a noble metal was supported and coated in the same manner as in Reference Example 1 to prepare a catalyst of Reference Example 6. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0148]
(Reference Example 7)
ZSM-5 type zeolite powder in the same manner as in Reference Example 1 except that the same amount of ZSM-5 type zeolite powder (“HSZ890HOA” manufactured by Tosoh Corporation, Si / Al ratio = 2000) was used instead of mordenite powder. A super strong zirconia layer was formed on the surface.
[0149]
Using this ZSM-5 type zeolite powder having a super strong zirconia layer, a noble metal was supported and coated in the same manner as in Reference Example 1 to prepare a catalyst of Reference Example 7. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0150]
(Reference Example 8)
100 parts of the same mordenite powder as in Reference Example 1, 100 parts of an aqueous 1% by weight hexaammineplatinum hydrate solution, and 200 parts of pure water are mixed, stirred for 1 hour, and then heated at 100 ° C. to keep moisture. The mixture was evaporated to dryness, dried at 120 ° C. for 2 hours and then calcined at 300 ° C. for 2 hours. Thus, Pt-supported mordenite powder was prepared.
[0151]
Next, 150 parts of Pt-supported mordenite powder, 200 parts of pure water and 55 parts of silica sol (solid content 35%) were mixed and stirred to prepare a slurry. Then, a cordierite-made honeycomb carrier base material (volume: 1.5 L) was prepared, dipped in the slurry and pulled up to blow off the excess slurry, dried at 100 ° C. for 2 hours, fired at 500 ° C. for 2 hours, and Reference Example 8 The catalyst was obtained. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0152]
(Reference Example 9)
100 parts of a commercially available mordenite powder (“HSZ660HOA” manufactured by Tosoh Corporation, Si / Al ratio = 30), 100 parts of a 1 wt% hexaammineplatinum hydrate solution and 200 parts of pure water were mixed. After stirring for a period of time, heating was continued at 100 ° C. to evaporate the moisture, followed by drying at 120 ° C. for 2 hours and further baking at 300 ° C. for 2 hours. Thus, Pt-supported mordenite powder was prepared.
[0153]
Next, 150 parts of Pt-supported mordenite powder, 200 parts of pure water and 55 parts of silica sol (solid content 35%) were mixed and stirred to prepare a slurry. Then, a cordierite-made honeycomb carrier base material (volume: 1.5 L) was prepared, dipped in the slurry, pulled up to blow off the excess slurry, dried at 100 ° C. for 2 hours, fired at 500 ° C. for 2 hours, and Reference Example 9 The catalyst was obtained. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0154]
(Reference Example 10)
A super strong zirconia layer is formed on the surface of the mordenite powder in the same manner as in Reference Example 1 except that the same amount of mordenite powder (“HSZ660HOA” manufactured by Tosoh Corporation, Si / Al ratio = 30) is used as the zeolite powder. did.
[0155]
Using this mordenite powder having an ultra-strong oxide zirconia layer, a noble metal was supported and coated in the same manner as in Reference Example 1 to prepare a catalyst of Reference Example 10. The amount of coating is 150 g per liter of the carrier substrate, and the amount of Pt supported is 1.5 g per liter of the carrier substrate.
[0156]
(Evaluation test)
Each of the above-mentioned catalysts is installed in the exhaust system of a 2400cc in-line four-cylinder diesel engine, and the endurance test for 25 hours is carried out by adjusting the gas temperature with catalyst to 600 ° C by the load at a constant speed of 3600 rpm. went.
[0157]
Each catalyst after the endurance test is installed in the engine exhaust system similar to the endurance test, and the load is changed so that the rotational speed changes in the range of 1000-2500 rpm as shown in FIG. Was added in the range of 300-1200 ppmC, and the maximum purification rates of HC and NO were measured. The results are shown in FIG.
[0158]
From FIG. 3, the catalysts of Reference Examples 1-7 show superior results in both the HC purification rate and the NO purification rate as compared with the catalysts of Reference Examples 8-10. And it turns out that the catalyst of the reference examples 1-3 shows the purification rate remarkably superior from the reference example 8, and presence of a super strong oxide layer has contributed remarkably to the improvement of a purification rate. Moreover, in the catalysts of Reference Examples 1 to 7, there was almost no difference in purification performance before and after the durability test, and the durability was excellent.
[0159]
On the other hand, since the catalyst of Reference Example 10 has a super strong acid oxide layer, the purification rate is higher than that of Reference Examples 8 and 9, but the purification rate is lower than that of Reference Examples 1 to 7. By the way, considering that the catalyst of Reference Example 10 had a slightly higher purification rate than that of Reference Example 1 before the durability test, the catalyst of Reference Example 10 had a small Si / Al ratio in the zeolite. It is thought that caking occurred inside and grain growth occurred in Pt due to de-Al, resulting in a significant reduction in purification performance.
[0160]
【The invention's effect】
That is, according to the exhaust gas purification method and exhaust gas purification catalyst of the present invention, NO in the exhaust gas containing excess oxygen. _x Can be efficiently purified, and NO _x NO is stable over a long period of time because of its excellent purification performance. _x It becomes possible to purify.
[0161]
Even when the exhaust gas temperature is low immediately after the start of operation or during deceleration, HC and NO _x NO in the exhaust gas that contains a lot of SOF, such as diesel engine exhaust gas _x Can be reduced and removed more efficiently.
[0162]
Therefore, the present invention can be used for an exhaust gas purification system of an automobile, _x Emission can be suppressed, and air pollution by automobile exhaust gas can be suppressed.
[Brief description of the drawings]
FIG. 1 is a graph showing operating conditions of an engine when measuring a purification rate.
FIG. 2 is a bar graph showing NO purification rates and HC purification rates after endurance tests of exhaust gas purification catalysts of Examples 1 to 12 and Comparative Examples 1 to 6.
FIG. 3 is a bar graph showing the NO purification rate and the HC purification rate after the durability test of the exhaust gas purification catalysts of Reference Examples 1 to 10.

Claims (12)

In a flue gas purification method for reducing and purifying nitrogen oxides in flue gas under an oxygen-excess atmosphere, a support layer comprising a hydrocarbon adsorbing capacity and comprising an HC adsorbent made of mordenite, ZSM-5, and Y-type zeolite A noble metal supported on the supporting layer and a solid superacid, and the supporting layer is super-oxidized zeolite having a molar ratio of silicon to aluminum (Si / Al) of 150 or more, a porous support and a rich atmosphere. Using an exhaust gas purifying catalyst that is supported on at least one of the porous carrier and the oxygen releasing material that is not supported on the zeolite .
The hydrocarbon is adsorbed and held by the HC adsorbent, the hydrocarbon released from the HC adsorbent is cracked by the solid super strong acid, and the nitrogen oxide in the exhaust gas is reduced using the hydrocarbon generated thereby as a reducing agent. An exhaust gas purification method comprising reduction purification.   The exhaust gas purification method according to claim 1, wherein the zeolite has a coating layer made of at least one of titania, silica, and zirconia, and the coating layer is superoxidized.   2. The exhaust gas purification method according to claim 1, wherein the oxygen release material is made of a ceria-zirconia composite oxide having a molar ratio Zr / Ce of 1 or less and has a coating layer made of at least one of titania, silica, and zirconia.   The exhaust gas purification method according to claim 3, wherein the coat layer is superoxidized.   2. The exhaust gas purification method according to claim 1, wherein the porous carrier is obtained by super-strongly oxidizing at least one selected from titania, silica, zirconia, and alumina coated with at least one of titania, silica, and zirconia. . An exhaust gas purifying catalyst for reducing and purifying nitrogen oxides in exhaust gas under an oxygen-excess atmosphere, and a support layer containing an HC adsorbent made of zeolite selected from mordenite, ZSM-5, and Y-type zeolite having hydrocarbon adsorption ability; A noble metal and a solid superacid supported on the support layer,
It said supported layer the molar ratio of silicon to aluminum (Si / Al) becomes more and zeolites superacid of over 150, the oxygen release material which releases oxygen in the porous support and the rich atmosphere, the noble metal the zeolite The exhaust gas-purifying catalyst is supported by at least one of the porous carrier and the oxygen release material.   The exhaust gas-purifying catalyst according to claim 6, wherein the zeolite has a coating layer made of at least one of titania, silica, and zirconia, and the coating layer is superoxidized.   The exhaust gas purifying catalyst according to claim 7, wherein the oxygen releasing material is made of a ceria-zirconia composite oxide having a molar ratio Zr / Ce of 1 or less and has a coating layer made of at least one of titania, silica and zirconia.   The exhaust gas-purifying catalyst according to claim 8, wherein the coating layer is superoxidized.   The exhaust gas purifying apparatus according to claim 6, wherein the porous carrier is obtained by super-oxidizing at least one selected from titania, silica, zirconia and alumina coated with at least one of titania, silica and zirconia. catalyst. Wherein the carrier layer Ir, Pd, Rh, In, catalysts for purification of exhaust gas according to claim 6 in which at least one of the NO _x oxidizing agent selected from the group consisting of Mn and Fe are supported. The exhaust gas purifying catalyst according to claim 6, further comprising a NO _x storage material.

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