JP5544921B2 - Exhaust gas purification catalyst - Google Patents
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Description
本発明は、Ｓ被毒耐性を高めた排ガス浄化用触媒に関する。 The present invention relates to an exhaust gas purifying catalyst having increased resistance to S poisoning.
従来の三元触媒技術では、貴金属（触媒金属）のシンタリング抑制を重視して、塩基性担体をベースとした触媒を採用してきた。特許文献１には、酸性担体であるＺｒＯ２−ＳｉＯ２複合酸化物と相対的に塩基性であるＡｌ２Ｏ３とから成る担体にＰｄを担持させた排ガス浄化用触媒が開示されている。 In the conventional three-way catalyst technology, a catalyst based on a basic support has been adopted with emphasis on suppression of sintering of a noble metal (catalyst metal). Patent Document 1 discloses an exhaust gas purifying catalyst in which Pd is supported on a carrier composed of ZrO 2 —SiO 2 composite oxide that is an acidic carrier and Al 2 O 3 that is relatively basic.
しかし、このような酸性担体と相対的に塩基性のアルミナとの組み合わせは、ＮＳＲ触媒としては高い触媒性能が得られても、三元触媒としては貴金属のシンタリングが問題となる（図７参照）。 However, such a combination of an acidic carrier and a relatively basic alumina has a problem of sintering a noble metal as a three-way catalyst even if high catalytic performance is obtained as an NSR catalyst (see FIG. 7). ).
また、近年、貴金属使用量を大幅に低減してきたため、排ガス中に含まれる硫黄（Ｓ）による被毒の影響が相対的に顕著となってきた（図８参照）。 Further, in recent years, since the amount of noble metal used has been greatly reduced, the influence of poisoning by sulfur (S) contained in the exhaust gas has become relatively significant (see FIG. 8).
そのため、シンタリング抑制効果を保持しつつ、硫黄被毒に対する耐性を確保することが求められている。 Therefore, it is required to ensure resistance to sulfur poisoning while maintaining the sintering suppression effect.
また、特許文献２には、Ｃｅ、Ｚｒ、Ａｌなどの金属の酸化物から成る基粒子と、この基粒子の表面の少なくとも一部に担持されたＰｔ、Ｒｈ、Ｐｄなどから成る貴金属とから成る触媒粒子が、特許文献３には、貴金属が担持された多孔質酸化物粉末と、ジルコニアなどから成る排ガス浄化用触媒が開示されているが、いずれも前述の問題に対する配慮はなされていない。 Patent Document 2 includes a base particle made of an oxide of a metal such as Ce, Zr, or Al, and a noble metal made of Pt, Rh, Pd or the like supported on at least a part of the surface of the base particle. Patent Document 3 discloses a catalyst for exhaust gas purification comprising a porous oxide powder carrying a noble metal and zirconia as catalyst particles, but none of the above-mentioned problems are taken into consideration.
また、例えばＰｄ触媒は、ＮＯｘ浄化活性、ＨＣ酸化活性に優れた性能を有するが、２層構成の触媒の上層に配置すると、Ｓ被毒の影響で十分な性能を発揮しない。Ｓ被毒の影響を回避するために、Ｐｄ触媒をガスが拡散し難い下層に配置し、Ｓ被毒に強いＲｈを上層に配置すると、コストメリットの高いＰｄの性能を十分に生かしきれない。
特許文献４に、上層のＰｄを含み、上層Ｒｈが４０質量％以下で、下層Ｒｈが６０質量％以上である２層構成の触媒が開示されている。しかし、上記の問題に対しては配慮されていない。
Further, for example, a Pd catalyst has excellent performance in NOx purification activity and HC oxidation activity. However, when it is disposed on the upper layer of a catalyst having a two-layer structure, it does not exhibit sufficient performance due to the influence of S poisoning. In order to avoid the influence of S poisoning, if the Pd catalyst is disposed in the lower layer where gas is difficult to diffuse and the Rh that is resistant to S poisoning is disposed in the upper layer, the performance of Pd with high cost merit cannot be fully utilized.
Patent Document 4 discloses a catalyst having a two-layer structure that includes Pd in the upper layer, the upper layer Rh is 40% by mass or less, and the lower layer Rh is 60% by mass or more. However, no consideration is given to the above problems.
本発明は、シンタリング抑制効果を保持しつつ、Ｓ被毒耐性を高めた排ガス浄化用触媒を提供することを目的とする。 An object of the present invention is to provide an exhaust gas purifying catalyst having an increased S poisoning resistance while maintaining a sintering suppression effect.
上記の目的を達成するために、第１発明の排ガス浄化用触媒は、貴金属を担持するジルコニアと、シリカとが複合して成ることを特徴とする。
更に、第２発明の排ガス浄化用触媒は、２層構成の触媒コート層を有し、上層が、貴金属を担持するジルコニアと、シリカとが複合して成ることを特徴とする。
In order to achieve the above object, the exhaust gas purifying catalyst of the first invention is characterized by comprising a composite of zirconia supporting a noble metal and silica.
Further, the exhaust gas purifying catalyst of the second invention has a two-layered catalyst coat layer, and the upper layer is a composite of zirconia supporting noble metal and silica.
第１発明の排ガス浄化用触媒は、貴金属を担持するジルコニアと、シリカとが混在することにより、Ｓ被毒耐性が顕著に向上する。
第２発明の排ガス浄化用触媒は、上記複合構造を２層構成の触媒の上層に適用することにより、上層／下層の組み合わせを最適化して触媒性能を向上させることができる。
In the exhaust gas purifying catalyst of the first invention, S poisoning resistance is remarkably improved by mixing zirconia supporting noble metal and silica.
The exhaust gas purifying catalyst of the second invention can improve the catalyst performance by optimizing the combination of the upper layer / lower layer by applying the composite structure to the upper layer of the catalyst having a two-layer structure.
本発明者は、貴金属を担持するジルコニア粒子と、シリカ粒子とを混合して排ガス浄化用触媒を構成すると、Ｓ被毒耐性が顕著に向上することを発見した。貴金属としては、Ｐｄ、Ｒｈ、Ｐｔなど、排ガス浄化用触媒に用いられる触媒金属を用いることができる。以下、貴金属としてＰｄを例に説明する。 The present inventor has discovered that when the zirconia particles supporting the noble metal and the silica particles are mixed to constitute an exhaust gas purification catalyst, the S poisoning resistance is remarkably improved. As the noble metal, a catalyst metal used for an exhaust gas purifying catalyst such as Pd, Rh, Pt or the like can be used. Hereinafter, Pd will be described as an example of the noble metal.
この効果は、貴金属がジルコニアに担持されずにシリカに担持されていても得られず、ジルコニアとシリカとが相互に固溶していても得られない。すなわち、図１に模式的に示すように、ジルコニア（ＺｒＯ２）粒子とシリカ（ＳｉＯ２）粒子とがそれぞれ相互に独立した粒子として存在し且つ両者が密接して混在・共存する複合状態でなくてはならない。この状態を〔Ｐｄ／ＺｒＯ２〕ＳｉＯ２と表示する。 This effect cannot be obtained even if the noble metal is supported on silica without being supported on zirconia, and cannot be obtained even if zirconia and silica are in solid solution with each other. That is, as schematically shown in FIG. 1, zirconia (ZrO 2 ) particles and silica (SiO 2 ) particles exist as independent particles, and are not in a mixed state in which both are closely mixed and coexisting. must not. This state is expressed as [Pd / ZrO 2 ] SiO 2 .
ＺｒＯ２担体にＰｄを担持したＰｄ／ＺｒＯ２触媒は、酸性担体上にＰｄを担持するよりも高分散に担持できるが、排ガス中の硫黄（Ｓ）分による活性低下が顕著である。本発明においては、Ｐｄ／ＺｒＯ２触媒にＳｉＯ２を複合させて〔Ｐｄ／ＺｒＯ２〕ＳｉＯ２触媒とすることで、高分散を維持しつつＳ被毒に対する耐性を大幅に高めることができる。 Pd / ZrO 2 catalyst supporting Pd on ZrO 2 carrier will be supported in a highly dispersed than supporting Pd on acidic carrier, reduction in activity due to sulfur (S) content in the exhaust gas is remarkable. In the present invention, by combining SiO 2 with a Pd / ZrO 2 catalyst to form a [Pd / ZrO 2 ] SiO 2 catalyst, the resistance to S poisoning can be greatly enhanced while maintaining high dispersion.
更に、これまで、フルサイズ触媒の基本構成として、上層Ｒｈ／下層Ｐｄの２層構成の触媒を用いているが、これはＰｄ触媒がＳ被毒の影響を強く受け、浄化率が大幅に悪化してしまうため、上層に配置できなかったためである。本発明の〔Ｐｄ／ＺｒＯ２〕ＳｉＯ２複合構造を上層に適用することにより、Ｐｄ触媒のＳ被毒耐性が高まり、従来の上層Ｒｈ／下層Ｐｄの２層構成の触媒に比べてＮＯｘ浄化性能を大幅に高めることができる。 Furthermore, up to now, the catalyst of the two-layer structure of upper layer Rh / lower layer Pd has been used as the basic structure of the full-size catalyst, but this is because the Pd catalyst is strongly affected by S poisoning and the purification rate is greatly deteriorated. This is because it could not be arranged in the upper layer. By applying the [Pd / ZrO 2 ] SiO 2 composite structure of the present invention to the upper layer, the S poisoning resistance of the Pd catalyst is increased, and the NOx purification performance is improved as compared with the conventional catalyst having a two-layer structure of upper layer Rh / lower layer Pd. Can be greatly increased.
以下、実施例により、本発明の排ガス浄化用触媒を詳細に説明する。 Hereinafter, the exhaust gas purifying catalyst of the present invention will be described in detail by way of examples.
〔第１発明の実施例〕
下記原料を種々に組み合わせて、本発明の規定による実施例および本発明の規定外の比較例の触媒を以下の手順および条件により作製した。
[Embodiment of the first invention]
Catalysts of Examples according to the present invention and Comparative Examples outside the present invention were prepared by the following procedures and conditions in various combinations of the following raw materials.
＜用いた原料＞
原料１：ＳｉＯ２粉末（「ナノテックＳｉＯ２」シーアイ化成製）
原料２：ＺｒＯ２粉末（「ＲＣ１００」第一稀元素製）
原料３：ＳｉＺｒＯ４粉末（「珪酸ジルコニウム」ナカライテスク製）
〔比較例１〕：〔Ｐｄ／ＺｒＯ２〕＋ＺｒＯ２
蒸発乾固法により、Ｐｄ含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料２（ＺｒＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＺｒＯ２を得た。
<Used raw materials>
Raw material 1: SiO 2 powder (“Nanotech SiO 2 ” manufactured by CI Kasei)
Raw material 2: ZrO 2 powder ("RC100" made by first rare element)
Raw material 3: SiZrO 4 powder (“Zirconium silicate” manufactured by Nacalai Tesque)
[Comparative Example 1]: [Pd / ZrO 2 ] + ZrO 2
By evaporation to dryness, Pd was supported on the raw material 2 (ZrO 2 ) from an aqueous palladium nitrate solution (produced by Cataler) having a Pd content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace, and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / ZrO 2 .
得られたＰｄ／ＺｒＯ２：１５ｇに対して、原料２（ＺｒＯ２）を１５ｇ混合し、自動乳鉢で１ｈ混合した。 15 g of raw material 2 (ZrO 2 ) was mixed with 15 g of the obtained Pd / ZrO 2 and mixed for 1 h in an automatic mortar.
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。 The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
この粉末に、ＣＩＰで約１tonの圧力を加え、約１ｍｍ角のペレットを成形して、比較例１の触媒サンプルとした。 A pressure of about 1 ton was applied to this powder with CIP to form a pellet of about 1 mm square, and a catalyst sample of Comparative Example 1 was obtained.
〔実施例１〕：９５wt％〔Ｐｄ／ＺｒＯ２〕＋５wt％ＳｉＯ２
蒸発乾固法により、Ｐｄ含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料２（ＺｒＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＺｒＯ２を得た。
[Example 1]: 95 wt% [Pd / ZrO 2 ] +5 wt% SiO 2
By evaporation to dryness, Pd was supported on the raw material 2 (ZrO 2 ) from an aqueous palladium nitrate solution (produced by Cataler) having a Pd content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace, and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / ZrO 2 .
得られたＰｄ／ＺｒＯ２：９５ｇに対して、原料１（ＳｉＯ２）を５ｇ混合し、自動乳鉢で１ｈ混合した。 5 g of raw material 1 (SiO 2 ) was mixed with 95 g of the obtained Pd / ZrO 2 and mixed for 1 h in an automatic mortar.
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。 The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
この粉末に、ＣＩＰで約１tonの圧力を加え、約１ｍｍ角のペレットを成形して、実施例１の触媒サンプルとした。 To this powder, a pressure of about 1 ton was applied with CIP to form a pellet of about 1 mm square, and a catalyst sample of Example 1 was obtained.
〔実施例２〕：７５wt％〔Ｐｄ／ＺｒＯ２〕＋２５wt％ＳｉＯ２
蒸発乾固法により、Ｐｄ含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料２（ＺｒＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＺｒＯ２を得た。
[Example 2]: 75 wt% [Pd / ZrO 2 ] +25 wt% SiO 2
By evaporation to dryness, Pd was supported on the raw material 2 (ZrO 2 ) from an aqueous palladium nitrate solution (produced by Cataler) having a Pd content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace, and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / ZrO 2 .
得られたＰｄ／ＺｒＯ２：７５ｇに対して、原料１（ＳｉＯ２）を２５ｇ混合し、自動乳鉢で１ｈ混合した。 25 g of raw material 1 (SiO 2 ) was mixed with 75 g of the obtained Pd / ZrO 2 and mixed for 1 h in an automatic mortar.
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。 The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
この粉末に、ＣＩＰで約１tonの圧力を加え、約１ｍｍ角のペレットを成形して、実施例２の触媒サンプルとした。 To this powder, a pressure of about 1 ton was applied by CIP to form a pellet of about 1 mm square to obtain a catalyst sample of Example 2.
〔実施例３〕：５０wt％〔Ｐｄ／ＺｒＯ２〕＋５０wt％ＳｉＯ２
蒸発乾固法により、Ｐｄ含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料２（ＺｒＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＺｒＯ２を得た。
[Example 3]: 50 wt% [Pd / ZrO 2 ] +50 wt% SiO 2
By evaporation to dryness, Pd was supported on the raw material 2 (ZrO 2 ) from an aqueous palladium nitrate solution (produced by Cataler) having a Pd content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace, and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / ZrO 2 .
得られたＰｄ／ＺｒＯ２：５０ｇに対して、原料１（ＳｉＯ２）を５０ｇ混合し、自動乳鉢で１ｈ混合した。 50 g of raw material 1 (SiO 2 ) was mixed with 50 g of the obtained Pd / ZrO 2 and mixed for 1 h in an automatic mortar.
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。 The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
この粉末に、ＣＩＰで約１tonの圧力を加え、約１ｍｍ角のペレットを成形して、実施例３の触媒サンプルとした。 To this powder, a pressure of about 1 ton was applied with CIP to form a pellet of about 1 mm square to obtain a catalyst sample of Example 3.
〔実施例４〕：２５wt％〔Ｐｄ／ＺｒＯ２〕＋７５wt％ＳｉＯ２
蒸発乾固法により、Ｐｄ含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料２（ＺｒＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＺｒＯ２を得た。
[Example 4]: 25 wt% [Pd / ZrO 2 ] +75 wt% SiO 2
By evaporation to dryness, Pd was supported on the raw material 2 (ZrO 2 ) from an aqueous palladium nitrate solution (produced by Cataler) having a Pd content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace, and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / ZrO 2 .
得られたＰｄ／ＺｒＯ２：２５ｇに対して、原料１（ＳｉＯ２）を７５ｇ混合し、自動乳鉢で１ｈ混合した。 75 g of raw material 1 (SiO 2 ) was mixed with 25 g of the obtained Pd / ZrO 2 and mixed for 1 h in an automatic mortar.
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。 The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
この粉末に、ＣＩＰで約１tonの圧力を加え、約１ｍｍ角のペレットを成形して、実施例４の触媒サンプルとした。 To this powder, a pressure of about 1 ton was applied with CIP to form a pellet of about 1 mm square to obtain a catalyst sample of Example 4.
〔比較例２〕：５０wt％〔Ｐｄ／ＳｉＯ２〕＋５０wt％ＳｉＯ２
蒸発乾固法により、Ｐｄ含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料１（ＳｉＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＳｉＯ２を得た。
[Comparative Example 2]: 50 wt% [Pd / SiO 2 ] +50 wt% SiO 2
By evaporation to dryness, Pd was supported on the raw material 1 (SiO 2 ) from an aqueous palladium nitrate solution (Cataler) having a Pd content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace, and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / SiO 2 .
得られたＰｄ／ＳｉＯ２：５０ｇに対して、原料１（ＳｉＯ２）を５０ｇ混合し、自動乳鉢で１ｈ混合した。 50 g of raw material 1 (SiO 2 ) was mixed with 50 g of the obtained Pd / SiO 2 and mixed for 1 h in an automatic mortar.
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。 The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
この粉末に、ＣＩＰで約１tonの圧力を加え、約１ｍｍ角のペレットを成形して、比較例２の触媒サンプルとした。 A pressure of about 1 ton was applied to this powder with CIP to form a pellet of about 1 mm square, and a catalyst sample of Comparative Example 2 was obtained.
〔比較例３〕：５０wt％〔Ｐｄ／ＳｉＯ２〕＋５０wt％ＺｒＯ２
蒸発乾固法により、Ｐｄ含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料１（ＳｉＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＳｉＯ２を得た。
[Comparative Example 3]: 50 wt% [Pd / SiO 2 ] +50 wt% ZrO 2
By evaporation to dryness, Pd was supported on the raw material 1 (SiO 2 ) from an aqueous palladium nitrate solution (Cataler) having a Pd content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace, and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / SiO 2 .
得られたＰｄ／ＳｉＯ２：５０ｇに対して、原料２（ＺｒＯ２）を５０ｇ混合し、自動乳鉢で１ｈ混合した。 50 g of raw material 2 (ZrO 2 ) was mixed with 50 g of the obtained Pd / SiO 2 and mixed for 1 h in an automatic mortar.
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。 The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
この粉末に、ＣＩＰで約１tonの圧力を加え、約１ｍｍ角のペレットを成形して、比較例３の触媒サンプルとした。 A pressure of about 1 ton was applied to this powder with CIP to form a pellet of about 1 mm square, and a catalyst sample of Comparative Example 3 was obtained.
〔比較例４〕：Ｐｄ／ＳｉＺｒＯ４
蒸発乾固法により、Ｐｄ含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料３（ＳｉＺｒＯ４）へＰｄを担持した。すなわち、薬液を担持した後の粉末を脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＳｉＺｒＯ４を得た。
[Comparative Example 4]: Pd / SiZrO 4
By evaporation to dryness, Pd was supported on the raw material 3 (SiZrO 4 ) from an aqueous palladium nitrate solution (Cataler) having a Pd content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace, and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / SiZrO 4 .
得られたＰｄ／ＳｉＺｒＯ４を自動乳鉢で１ｈ混合した。 The obtained Pd / SiZrO 4 was mixed for 1 h in an automatic mortar.
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。 The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
この粉末に、ＣＩＰで約１tonの圧力を加え、約１ｍｍ角のペレットを成形して、比較例４の触媒サンプルとした。 A pressure of about 1 ton was applied to this powder with CIP to form a pellet of about 1 mm square, and a catalyst sample of Comparative Example 4 was obtained.
実施例１〜４および比較例１〜４で得られた触媒サンプルについて、下記の条件でＳ被毒処理を行なった。 The catalyst samples obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were subjected to S poisoning treatment under the following conditions.
＜Ｓ被毒処理の条件＞
ストイキ＋ＳＯ２（５０ppm）の雰囲気中で、４００℃×１ｈ加熱。
<Conditions for S poisoning treatment>
Heated at 400 ° C. for 1 h in an atmosphere of stoiki + SO 2 (50 ppm).
Ｓ被毒処理の処理前、処理中、処理後に、それぞれ触媒活性を下記の条件で評価した。 The catalytic activity was evaluated under the following conditions before, during and after the S poisoning treatment.
＜触媒活性の評価条件＞
《１》Ｓ被毒処理なし
調整した触媒サンプルそれぞれについて、固定床反応装置を用いて、以下の条件で評価した。
<Evaluation conditions for catalyst activity>
<< 1 >> No S poisoning treatment Each adjusted catalyst sample was evaluated using a fixed bed reactor under the following conditions.
触媒ペレット：３．０ｇ
床温度：４００℃
ガス流量：１５Ｌ／min
ガス組成：0.15％NO＋0.7％O２＋0.65％CO＋0.1％C３H６＋10％CO２＋3％H２O
すなわち、アンダーフロアー触媒の代表的な使用温度域である４００℃でのストイキ条件にて行なった。
Catalyst pellets: 3.0g
Floor temperature: 400 ° C
Gas flow rate: 15L / min
Gas composition: 0.15% NO + 0.7% O 2 + 0.65% CO + 0.1% C 3 H 6 + 10% CO 2 + 3% H 2 O
That is, it was carried out under stoichiometric conditions at 400 ° C., which is a typical operating temperature range of the underfloor catalyst.
《２》Ｓ被毒処理中
上記《１》の評価条件にSO２ガス50ppmを導入し、SO２を含む反応ガスに触媒サンプルを１．５ｈ曝した後の浄化率を測定した。
<< 2 >> During
《３》Ｓ被毒処理後
上記《２》の処理後、SO２ガスの導入を停止し、１０分後の活性を測定した（SO２ガス以外の条件は不変）。
"3" S after the process of the treatment of poisoning after the "2", to stop the introduction of SO 2 gas, the activity was measured after 10 min (SO 2 conditions other than gas unchanged).
表１に、サンプル中のＳｉＯ２含有量と、Ｓ被毒処理なし・処理中・処理後それぞれの触媒活性の評価とをまとめて示す。更に、図２、図３、図４に、サンプル中のＳｉＯ２含有量に対するＳ被毒処理なし、処理中、処理後の触媒活性の評価をそれぞれ示す。なお、図中では、ＳｉＯ２を「Ｓｉ」、ＺｒＯ２を「Ｚｒ」と略記し、例えば〔Ｐｄ／ＺｒＯ２〕ＳｉＯ２の担持形態を「Ｓｉ−Ｚｒ」と表記した。 Table 1 summarizes the SiO 2 content in the sample and the evaluation of the respective catalytic activities without, during and after the S poisoning treatment. Further, FIGS. 2, 3 and 4 show evaluations of catalytic activity without, during and after the treatment with respect to the SiO 2 content in the sample. In the figure, SiO 2 is abbreviated as “Si”, ZrO 2 is abbreviated as “Zr”, and for example, the supported form of [Pd / ZrO 2 ] SiO 2 is denoted as “Si—Zr”.
＜触媒活性の評価結果＞
≪Ｓ被毒処理なし≫
Ｓ被毒処理なしの場合は、表１および図２に示すように、本発明の規定による〔Ｐｄ／ＺｒＯ２〕ＳｉＯ２の担持形態を有する実施例１〜４は９５〜９７％の高い触媒活性を発揮した。本発明の規定外の比較例１〜４については、〔Ｐｄ／ＺｒＯ２〕ＺｒＯ２の担持形態を有する比較例１は、９６％と本発明の実施例１〜４と同等の高い触媒活性を発揮した。〔Ｐｄ／ＳｉＯ２〕ＳｉＯ２の担持形態を有する比較例２および〔Ｐｄ／ＳｉＯ２〕ＺｒＯ２の担持形態を有する比較例３はいずれも９２％と若干劣り、更にＰｄ／ＳｉＺｒＯ４の担持形態を有する比較例４は、７９％とかなり劣る。
<Evaluation results of catalyst activity>
≪No S poisoning treatment≫
In the case of no S poisoning treatment, as shown in Table 1 and FIG. 2, Examples 1 to 4 having a supported form of [Pd / ZrO 2 ] SiO 2 according to the definition of the present invention are high catalysts of 95 to 97%. Demonstrated activity. For Comparative Examples 1 to 4 outside the scope of the present invention, Comparative Example 1 having a supported form of [Pd / ZrO 2 ] ZrO 2 has a high catalytic activity of 96%, which is equivalent to that of Examples 1 to 4 of the present invention. Demonstrated. [Pd / SiO 2] Comparative Example 3 is inferior 92% and slightly both having a supported form of Comparative Example 2 and [Pd / SiO 2] ZrO 2 having a SiO 2 of supported form, further supported form of Pd / SiZrO 4 Comparative Example 4 having
これは、ＳｉＯ２（比較例２、３）およびＳｉＺｒＯ４（比較例４）には貴金属Ｐｄを高分散に担持できないためであり、高分散を維持できないため担体の機能として不十分になるからである。 This is because SiO 2 (Comparative Examples 2 and 3) and SiZrO 4 (Comparative Example 4) cannot support the noble metal Pd in a highly dispersed state, and cannot maintain a highly dispersed state, so that the function of the support becomes insufficient. is there.
≪Ｓ被毒処理中≫
Ｓ被毒処理中の触媒活性は、表１および図３に示すように、本発明の実施例１〜４は４８〜５６％と、比較例１〜４の４３〜４６％に比べて優れている。これは、ＳｉＯ２を添加したことにより、Ｐｄ／ＺｒＯ２触媒の性質がＳＯ２は酸化し難く、ＮＯｘは酸化し易く変化したことにより、高い触媒活性を維持できたと考えられる。
≪Under S poisoning treatment≫
As shown in Table 1 and FIG. 3, the catalytic activity during the S poisoning treatment is 48 to 56% in Examples 1 to 4 of the present invention, which is superior to 43 to 46% in Comparative Examples 1 to 4. Yes. This is probably because the addition of SiO 2 changed the properties of the Pd / ZrO 2 catalyst so that SO 2 was difficult to oxidize and NOx was easily oxidized, so that high catalytic activity could be maintained.
≪Ｓ被毒処理後≫
Ｓ被毒処理後の触媒活性は、表１および図４に示すように、本発明の実施例１〜４は７６〜８５％と、比較例１〜４の６８〜７３％に比べて著しく優れている。これは、ＳｉＯ２を共存させることで、ＳｉＯ２自体はＳを溜めずに活性を発現でき、かつ、蓄積したＳを離脱し易いため、Ｓ被毒処理後に高い触媒活性を発揮できると考えられる。特に、ＳｉＯ２含有量５〜５０％の範囲は、Ｓ被毒耐性の向上が特に顕著であった。
≪After S poisoning treatment≫
As shown in Table 1 and FIG. 4, the catalytic activity after the S poisoning treatment is 76 to 85% in Examples 1 to 4 of the present invention, which is remarkably superior to 68 to 73% in Comparative Examples 1 to 4. ing. This is because the coexistence of SiO 2, is considered to SiO 2 itself can express activity without pooled S, and liable to leave the accumulated S, can exhibit high catalytic activity following S-poisoning treatment . In particular, when the SiO 2 content is in the range of 5 to 50%, the improvement in S poisoning resistance was particularly remarkable.
〔第２発明の実施例〕
上記原料を種々に組み合わせて、２層コート構成で、本発明の規定による実施例および本発明の規定外の比較例の触媒を以下の手順および条件により作製した。
[Embodiment of the second invention]
The above-mentioned raw materials were combined in various ways, and in the two-layer coating configuration, the catalyst according to the example of the present invention and the comparative example outside of the present invention were prepared according to the following procedures and conditions.
＜触媒層成分１＞ Ｒｈ／ＺｒＯ２
蒸発乾固法を用いて、貴金属含有量２．７５wt％の硝酸ロジウム水溶液（キャタラー製）から原料２（ＺｒＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を、脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｒｈ／ＺｒＯ２を得た。
なお、Ｒｈの担持量は、全体の粉末に対して０．２５wt％となるように調整した。
<Catalyst layer component 1> Rh / ZrO 2
Using an evaporation to dryness method, Pd was supported on the raw material 2 (ZrO 2 ) from a rhodium nitrate aqueous solution (manufactured by Cataler) having a noble metal content of 2.75 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Rh / ZrO 2 .
The loading amount of Rh was adjusted to be 0.25 wt% with respect to the entire powder.
＜触媒層成分２＞ ５０wt％〔Ｐｄ／ＺｒＯ２〕＋５０wt％ＳｉＯ２
蒸発乾固法を用いて、貴金属含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料２（ＺｒＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を、脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＺｒＯ２を得た。
得られたＰｄ／ＺｒＯ２：２．５０ｇに対して、原料１（ＳｉＯ２粉末）５０ｇを混合し、自動乳鉢で１ｈ混合した。
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。
<Catalyst layer component 2> 50 wt% [Pd / ZrO 2 ] +50 wt% SiO 2
Using an evaporation to dryness method, Pd was supported on the raw material 2 (ZrO 2 ) from an aqueous palladium nitrate solution (Cataler) having a noble metal content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / ZrO 2 .
50 g of raw material 1 (SiO 2 powder) was mixed with the obtained Pd / ZrO 2 : 2.50 g and mixed for 1 h in an automatic mortar.
The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
＜触媒層成分３＞ Ｐｄ／ＺｒＯ２
蒸発乾固法を用いて、貴金属含有量８．２wt％の硝酸パラジウム水溶液（キャタラー製）から原料２（ＺｒＯ２）へＰｄを担持した。すなわち、薬液を担持した後の粉末を、脱脂炉で１２０℃×１２ｈ乾燥後、電気炉で６００℃×５ｈの焼成を行い、Ｐｄ／ＺｒＯ２を得た。
なお、Ｐｄの担持量は、全体の粉末に対して０．５wt％となるように調整した。
上記で調製した各触媒層成分を用いて以下の２層構成の触媒を作製した。
<Catalyst layer component 3> Pd / ZrO 2
Using an evaporation to dryness method, Pd was supported on the raw material 2 (ZrO 2 ) from an aqueous palladium nitrate solution (Cataler) having a noble metal content of 8.2 wt%. That is, the powder after supporting the chemical solution was dried at 120 ° C. for 12 hours in a degreasing furnace and then fired at 600 ° C. for 5 hours in an electric furnace to obtain Pd / ZrO 2 .
The amount of Pd supported was adjusted to 0.5 wt% with respect to the total powder.
Using the catalyst layer components prepared above, the following two-layer catalyst was prepared.
〔実施例５〕
触媒層成分が、下層《Ｒｈ／ＺｒＯ２》、上層《５０wt％〔Ｐｄ／ＺｒＯ２〕＋５０wt％ＳｉＯ２》である２層構成の触媒を作製した。
（１）下層コート
θ-Ａｌ２Ｏ３１７．７ｇ、触媒層成分１（Ｒｈ／ＺｒＯ２）１８．３９ｇ、水酸化アルミニウム粉末１．０５ｇ、４０％硝酸アルミニウム水溶液２２．６ｇ、精製水７３．３ｇを、３００ｍｌポリビーカーに入れて、ミキサーで３０分攪拌した。その後、ボールミルにて３ｈ混合し、スラリーを調整した。
このスラリーを、３５ｃｃセラミックハニカム（φ３０ｍｍ×Ｌ５０ｍｍ、４００セル／４ミル、ＮＧＫ製）に均一に流し込み、余分なスラリーを吹き払った後、脱脂炉で２５０℃×２ｈ乾燥し、その後、５００℃×２ｈ焼成した。その時のコート量は４ｇ／個となるように調製した。
Example 5
A catalyst having a two-layer structure in which the catalyst layer components were a lower layer << Rh / ZrO 2 >> and an upper layer << 50 wt% [Pd / ZrO 2 ] +50 wt% SiO 2 >> was prepared.
(1) Lower layer coat θ-Al 2 O 3 17.7 g, catalyst layer component 1 (Rh / ZrO 2 ) 18.39 g, aluminum hydroxide powder 1.05 g, 40% aluminum nitrate aqueous solution 22.6 g, purified water 73. 3 g was placed in a 300 ml poly beaker and stirred with a mixer for 30 minutes. Thereafter, the mixture was mixed for 3 hours with a ball mill to prepare a slurry.
This slurry was uniformly poured into a 35 cc ceramic honeycomb (φ30 mm × L50 mm, 400 cell / 4 mil, made by NGK), and after excess slurry was blown off, it was dried at 250 ° C. × 2 h in a degreasing furnace, and then 500 ° C. × Baked for 2 h. The coating amount at that time was adjusted to 4 g / piece.
（２）上層コート
θ-Ａｌ２Ｏ３１７．７ｇ、触媒層成分２（５０wt％〔Ｐｄ／ＺｒＯ２〕＋５０wt％ＳｉＯ２）１８．３９ｇ、水酸化アルミニウム粉末１．０５ｇ、４０％硝酸アルミニウム水溶液２２．６ｇ、精製水７３．３ｇを、３００ｍｌポリビーカーに入れて、ミキサーで３０分攪拌した。その後、ボールミルにて３ｈ混合し、スラリーを調整した。
このスラリーを、先に調製した下層コート済の３５ｃｃセラミックハニカム（φ３０ｍｍ×Ｌ５０ｍｍ、４００セル／４ミル、ＮＧＫ製）に均一に流し込み、余分なスラリーを吹き払った後、脱脂炉で２５０℃×２ｈ乾燥し、その後、５００℃×２ｈ焼成した。その時のコート量は８ｇ／個となるように調製した。
(2) Upper layer coat θ-Al 2 O 3 17.7 g, catalyst layer component 2 (50 wt% [Pd / ZrO 2 ] +50 wt% SiO 2 ) 18.39 g, aluminum hydroxide powder 1.05 g, 40% aluminum nitrate aqueous solution 22.6 g and 73.3 g of purified water were placed in a 300 ml poly beaker and stirred with a mixer for 30 minutes. Thereafter, the mixture was mixed for 3 hours with a ball mill to prepare a slurry.
This slurry was uniformly poured into the 35cc ceramic honeycomb (φ30 mm × L50 mm, 400 cell / 4 mil, manufactured by NGK) previously coated with the lower layer, and after excess slurry was blown off, 250 ° C. × 2 h in a degreasing furnace Then, it was baked at 500 ° C. for 2 hours. The coating amount at that time was adjusted to 8 g / piece.
〔比較例５〕
触媒層成分が、下層《Ｐｄ／ＺｒＯ２》、上層《５０wt％〔Ｐｄ／ＺｒＯ２〕＋５０wt％ＳｉＯ２》である２層構成の触媒を作製した。
これは実施例５において、触媒層成分１に代えて触媒層成分３を用いた以外は、実施例５と同様の手順および条件にて調製した。
[Comparative Example 5]
A catalyst having a two-layer structure in which the catalyst layer components were a lower layer << Pd / ZrO 2 >> and an upper layer << 50 wt% [Pd / ZrO 2 ] +50 wt% SiO 2 >> was prepared.
This was prepared in the same procedure and conditions as in Example 5, except that catalyst layer component 3 was used instead of catalyst layer component 1 in Example 5.
〔比較例６〕
触媒層成分が、下層《５０wt％〔Ｐｄ／ＺｒＯ２〕＋５０wt％ＳｉＯ２》、上層《Ｐｄ／ＺｒＯ２》である２層構成の触媒を作製した。
これは比較例５において、下層を形成する実施例５の工程（１）と、上層を形成する実施例５の工程（２）の順序を逆にして調整した。
[Comparative Example 6]
A catalyst having a two-layer structure in which the catalyst layer components were a lower layer << 50 wt% [Pd / ZrO 2 ] +50 wt% SiO 2 >> and an upper layer << Pd / ZrO 2 >> was prepared.
This was adjusted in the comparative example 5 by reversing the order of the step (1) in Example 5 for forming the lower layer and the step (2) in Example 5 for forming the upper layer.
〔実施例６〕
実施例５において、触媒層成分２の量を一定として、Ａｌ２Ｏ３含有率がその７１wt％となるように、θ-Ａｌ２Ｏ３量を調整した。その他の工程は実施例５と同様であった。
Example 6
In Example 5, the amount of the catalyst layer component 2 was constant, and the amount of θ-Al 2 O 3 was adjusted so that the Al 2 O 3 content was 71 wt%. Other steps were the same as in Example 5.
〔実施例７〕
実施例５において、触媒層成分２の量を一定として、Ａｌ２Ｏ３含有率がその６５wt％となるように、θ-Ａｌ２Ｏ３量を調整した。その他の工程は実施例５と同様であった。
Example 7
In Example 5, the amount of catalyst layer component 2 was constant, and the amount of θ-Al 2 O 3 was adjusted so that the Al 2 O 3 content was 65 wt%. Other steps were the same as in Example 5.
〔実施例８〕
実施例５において、触媒層成分２の量を一定として、Ａｌ２Ｏ３含有率がその６５wt％となるように、θ-Ａｌ２Ｏ３量を調整した。その他の工程は実施例５と同様であった。
Example 8
In Example 5, the amount of catalyst layer component 2 was constant, and the amount of θ-Al 2 O 3 was adjusted so that the Al 2 O 3 content was 65 wt%. Other steps were the same as in Example 5.
実施例５〜８および比較例１〜２で得られた２層構成の触媒サンプルについて、下記の条件でＳ被毒処理を行なった。 The two-layered catalyst samples obtained in Examples 5 to 8 and Comparative Examples 1 and 2 were subjected to S poisoning treatment under the following conditions.
＜Ｓ被毒処理の条件＞
ストイキ＋ＳＯ２（５０ppm）の雰囲気中で、４００℃×１ｈ加熱。
<Conditions for S poisoning treatment>
Heated at 400 ° C. for 1 h in an atmosphere of stoiki + SO 2 (50 ppm).
Ｓ被毒処理の処理前、処理中に、それぞれ触媒活性を下記の条件で評価した。
＜触媒活性の評価条件＞
《１》Ｓ被毒処理なし
調整した触媒サンプルそれぞれについて、固定床反応装置を用いて、以下の条件で評価した。
Before and during the S poisoning treatment, the catalytic activity was evaluated under the following conditions.
<Evaluation conditions for catalyst activity>
<< 1 >> No S poisoning treatment Each adjusted catalyst sample was evaluated using a fixed bed reactor under the following conditions.
触媒ペレット：３５ｃｃ（サンプル１個当たり）
床温度：４００℃
ガス流量：３０／min
ガス組成：0.15％NO＋0.7％O２＋0.65％CO＋0.1％C３H６＋10％CO２＋3％H２O
すなわち、アンダーフロアー触媒の代表的な使用温度域である４００℃でのストイキ条件にて行なった。
Catalyst pellet: 35cc (per sample)
Floor temperature: 400 ° C
Gas flow rate: 30 / min
Gas composition: 0.15% NO + 0.7% O 2 + 0.65% CO + 0.1% C 3 H 6 + 10% CO 2 + 3% H 2 O
That is, it was carried out under stoichiometric conditions at 400 ° C., which is a typical operating temperature range of the underfloor catalyst.
《２》Ｓ被毒処理中
上記《１》の評価条件にSO２ガス50ppmを導入し、SO２を含む反応ガスに触媒サンプルを１．５ｈ曝した後の浄化率を測定した。
表２に、各サンプルについて、コート層Ａｌ２Ｏ３含有率と、Ｓ被毒処理なし・Ｓ被毒処理中の触媒活性の評価とをまとめて示す。更に、図５、６に、Ａｌ２Ｏ３含有率に対するＳ被毒処理なし、Ｓ被毒処理中の評価をそれぞれ示す。
<< 2 >> During
Table 2 summarizes the coating layer Al 2 O 3 content and the evaluation of the catalytic activity during the S poisoning treatment without the S poisoning treatment for each sample. Furthermore, FIGS. 5 and 6 show the evaluation during the S poisoning treatment without the S poisoning treatment with respect to the Al 2 O 3 content.
表２、図５に示すように、Ｓ被毒のない場合は、本発明の規定範囲内の実施例と本発明の規定範囲外の比較例との間に、触媒活性の差はほとんど認められない。
表２、図６に示すように、Ｓ被毒処理中の触媒活性は、実施例は比較例に対して明らかに優れている。
また、実施例５と、比較例５および比較例６とを比較すると、単純にＰｄ／ＺｒＯ２を上層に配した場合、Ｒｈ／ＺｒＯ２を配置した場合に比べて、明らかに性能が劣る。
実施例１〜４の相互比較から、上層のＰｄ層（５０wt％〔Ｐｄ／ＺｒＯ２〕＋５０wt％シリカ）中のＡｌ２Ｏ３含有率が４５〜７０％であることが望ましい。
Ａｌ２Ｏ３は、触媒コート層を形成するために必須であり、除外することはできない。
As shown in Table 2 and FIG. 5, in the absence of S poisoning, there is almost no difference in catalytic activity between the examples within the specified range of the present invention and the comparative examples outside the specified range of the present invention. Absent.
As shown in Table 2 and FIG. 6, the catalyst activity during the S poisoning treatment is clearly superior to the comparative example.
Moreover, when Example 5 is compared with Comparative Example 5 and Comparative Example 6, when Pd / ZrO 2 is simply arranged in the upper layer, the performance is clearly inferior compared with the case where Rh / ZrO 2 is arranged.
From the mutual comparison of Examples 1 to 4, it is desirable that the Al 2 O 3 content in the upper Pd layer (50 wt% [Pd / ZrO 2 ] +50 wt% silica) is 45 to 70%.
Al 2 O 3 is essential for forming the catalyst coat layer and cannot be excluded.
本発明によれば、シンタリング抑制効果を保持しつつ、Ｓ被毒耐性を高めた排ガス浄化用触媒が提供される。
（態様１）
貴金属を担持するジルコニアと、シリカとが複合して成る排ガス浄化用触媒。
（態様２）
態様１において、前記シリカの含有量が排ガス浄化用触媒の５〜５０wt％であることを特徴とする排ガス浄化用触媒。
（態様３）
２層構成の触媒コート層を有し、上層が、貴金属を担持するジルコニアと、シリカとが複合して成る排ガス浄化用触媒。
（態様４）
態様３において、前記上層が４５〜７０wt％のアルミナを含有することを特徴とする排ガス浄化用触媒。
ADVANTAGE OF THE INVENTION According to this invention, the catalyst for exhaust gas purification which improved S poisoning tolerance, maintaining the sintering suppression effect is provided.
(Aspect 1)
An exhaust gas purifying catalyst comprising a composite of zirconia supporting noble metal and silica.
(Aspect 2)
The exhaust gas purification catalyst according to aspect 1, wherein the silica content is 5 to 50 wt% of the exhaust gas purification catalyst.
(Aspect 3)
An exhaust gas purifying catalyst having a two-layer catalyst coat layer, the upper layer comprising a composite of zirconia supporting a noble metal and silica.
(Aspect 4)
The exhaust gas purifying catalyst according to aspect 3, wherein the upper layer contains 45 to 70 wt% of alumina.
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| JP2010037643A JP5544921B2 (en) | 2009-11-18 | 2010-02-23 | Exhaust gas purification catalyst |
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| JP4265561B2 (en) * | 2005-04-04 | 2009-05-20 | 株式会社デンソー | Automobile exhaust gas purification catalyst body |
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