JP2012011308A - Exhaust gas purifying catalyst and method for producing the same - Google Patents
Exhaust gas purifying catalyst and method for producing the same Download PDFInfo
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Abstract
Description
本発明は、例えば、自動車排ガス中の有害物質を除去する排ガス浄化触媒及びこの排ガス浄化触媒の製造方法に関する。 The present invention relates to, for example, an exhaust gas purification catalyst for removing harmful substances in automobile exhaust gas and a method for producing the exhaust gas purification catalyst.
例えば自動車の排ガス中に含まれる窒素酸化物や一酸化炭素、炭化水素は環境規制の対象となっており、三元触媒（以下、排ガス浄化触媒という）はこれらの物質を分解して排ガスを浄化してから大気へと排出する役割を果たしている。排ガス浄化触媒は、例えばアルミナなどの担体に、白金（Ｐｔ）やパラジウム（Ｐｄ）、ロジウム（Ｒｈ）などの貴金属を活性金属として担持させたものが一般的に知られている。この排ガス浄化触媒は、例えばエンジンの出口部付近に配置され、高温の排ガスと接触させることにより汚染物質を分解する活性を得ている。 For example, nitrogen oxides, carbon monoxide, and hydrocarbons contained in automobile exhaust gas are subject to environmental regulations, and a three-way catalyst (hereinafter referred to as exhaust gas purification catalyst) decomposes these substances to purify exhaust gas. After that, it plays a role in discharging into the atmosphere. As the exhaust gas purification catalyst, a catalyst in which a noble metal such as platinum (Pt), palladium (Pd), or rhodium (Rh) is supported as an active metal on a carrier such as alumina is generally known. This exhaust gas purification catalyst is disposed, for example, in the vicinity of the outlet of the engine, and has an activity of decomposing pollutants by contacting with high temperature exhaust gas.
一般的に、排ガス浄化触媒は例えば１００ｍ２／ｇ以上もの比表面積を有する担体の表面に粒子径の小さな活性金属を均一に分散担持することにより、汚染物質と活性金属との接触効率を向上させるといった構造的な効果を利用して触媒の活性を高めている。ところが排ガス浄化触媒は、高温の排ガスと長期間接触すると、担体の比表面積が低下したり、活性金属が凝集して粒子径が大きくなったりするため、次第にこうした構造的な効果が失われて触媒の活性が低下してしまうシンタリングと呼ばれる現象が知られている。 In general, an exhaust gas purification catalyst improves the contact efficiency between a pollutant and an active metal by uniformly dispersing and supporting an active metal having a small particle size on the surface of a carrier having a specific surface area of, for example, 100 m 2 / g or more. Utilizing such structural effects, the activity of the catalyst is enhanced. However, when the exhaust gas purification catalyst is brought into contact with high temperature exhaust gas for a long period of time, the specific surface area of the carrier decreases or the active metal aggregates to increase the particle size. There is a known phenomenon called sintering, in which the activity of is reduced.
このため従来の排ガス浄化触媒は、シンタリングによる活性の低下を見越して、使用開始時の必要量よりも例えば３％程度多い活性金属を担持しておくことにより、構造的な効果が失われた後も必要な活性を維持する方策が採られてきた。しかしながらこの方策は、使用開始後、当面の期間中に必要な量以上の活性金属を触媒に担持する必要があるため、触媒コストへの影響が大きく、排ガス処理システムを高額にする要因となっていた。 For this reason, the conventional exhaust gas purification catalyst has lost its structural effect by supporting, for example, about 3% more active metal than the required amount at the start of use in anticipation of a decrease in activity due to sintering. Later, measures have been taken to maintain the necessary activity. However, this measure has a large impact on the catalyst cost because it is necessary to support the catalyst with an amount of active metal more than necessary for the time being after the start of use, and this is a factor that makes the exhaust gas treatment system expensive. It was.
特許文献１には、スピネル構造を持つＢａＡｌ２Ｏ４を含む排ガス浄化触媒が記載されており、当該触媒は高温雰囲気下で使用しても活性金属が凝集しにくい点と、それでも活性が低下してしまった場合には活性金属を再分散させる再生処理が可能である点とに特徴を有している。
特許文献２には、触媒作用を有する貴金属と、この貴金属が担持される第１の酸化物と、この触媒貴金属が担持された第１の酸化物を包む第２の酸化物とを少なくとも有する触媒粒子ユニットを備え、この触媒粒子ユニットが複数個集まってなる触媒粉末中に、助触媒成分である遷移元素、アルカリ土類金属元素、アルカリ金属元素、希土類元素から選ばれる少なくとも１種の化合物を含むことを特徴とする排気ガス浄化触媒が開示されている。
本発明はこのような事情の下になされたものであり、その目的は、活性金属の必要量が少なく、高温の条件下で長期間使用しても活性が低下し難い排ガス浄化触媒及びその製造方法を提供することにある。 The present invention has been made under such circumstances, and an object of the present invention is to provide an exhaust gas purifying catalyst which requires a small amount of active metal and whose activity is hardly lowered even when used for a long time under a high temperature condition and its production. It is to provide a method.
本出願における第１の発明は、第１の細孔径領域と、この第１の細孔径領域よりも細孔径の大きな第２の細孔径領域とに細孔径分布のピークを有するバイモーダル構造のＢａＡｌ１２Ｏ１９と、ＺｒＯ２と、を含む担体であって、ＢａＡｌ１２Ｏ１９に対するＺｒＯ２の質量比が１：０．１〜１：２０の範囲にある担体に活性金属が担持されていることを特徴とする排ガス浄化触媒である。 The first invention in the present application is directed to a BaAl having a bimodal structure having a peak of a pore size distribution in a first pore size region and a second pore size region having a pore size larger than the first pore size region. An active metal is supported on a support containing 12 O 19 and ZrO 2 and having a mass ratio of ZrO 2 to BaAl 12 O 19 in the range of 1: 0.1 to 1:20. An exhaust gas purification catalyst characterized by the above.
本出願における第２の発明は、前記細孔径分布において、第１の細孔径領域は３．４ｎｍ以上、５．３ｎｍ以下であり、第２の細孔径領域は５４ｎｍ以上、２００ｎｍ以下であることを特徴とする前記排ガス浄化触媒である。
本出願における第３の発明は、前記排ガス浄化触媒の比表面積が０．１ｍ２／ｇ以上、１１０ｍ２／ｇ以下の範囲であることを特徴とする前記排ガス浄化触媒である。
本出願における第４の発明は、前記活性金属は、Ｐｔ、Ｐｄ、Ｒｈ、Ｒｕ、Ｏｓ、Ｉｒ、Ａｕ及びＡｇからなる貴金属群から選ばれる少なくとも１種類以上の活性金属であることを特徴とする前記排ガス浄化触媒である。
本出願における第５の発明は、前記活性金属の担持量が、前記排ガス浄化触媒重量の０．０１重量％以上、２．０重量％以下の範囲であることを特徴とする前記排ガス浄化触媒である。
In a second aspect of the present application, in the pore size distribution, the first pore size region is 3.4 nm or more and 5.3 nm or less, and the second pore size region is 54 nm or more and 200 nm or less. The exhaust gas purifying catalyst is characterized.
A third invention in the present application is the exhaust gas purification catalyst, wherein a specific surface area of the exhaust gas purification catalyst is in a range of 0.1 m 2 / g or more and 110 m 2 / g or less.
According to a fourth invention of the present application, the active metal is at least one active metal selected from a noble metal group consisting of Pt, Pd, Rh, Ru, Os, Ir, Au, and Ag. The exhaust gas purification catalyst.
A fifth invention of the present application is the exhaust gas purification catalyst, wherein the amount of the active metal supported is in the range of 0.01% by weight or more and 2.0% by weight or less of the weight of the exhaust gas purification catalyst. is there.
本出願における第６の発明は、次の（１）〜（３）の工程を含むことを特徴とする排ガス浄化触媒の製造方法である。
（１）アルミニウム含有化合物、第２の細孔径領域に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９、ＢａＡｌ２Ｏ４及び有機酸を含む混合物であって、この混合物中のアルミニウムとバリウムのモル比が１：０．０２〜１：０．１の範囲であり、アルミニウムと有機酸のモル比が１：０．１〜１：０．５の範囲であるものを７００℃以上、１３００℃以下の温度で焼成し、第１の細孔径領域と、この第１の細孔径領域よりも細孔径の大きな前記第２の細孔径領域とに細孔径分布のピークを有するバイモーダル構造のＢａＡｌ１２Ｏ１９を調製する工程。
（２）このバイモーダル構造のＢａＡｌ１２Ｏ１９とＺｒＯ２とを混合して担体を調製する工程。
（３）前記担体にＰｔ、Ｐｄ、Ｒｈ、Ｒｕ、Ｏｓ、Ｉｒ、Ａｕ及びＡｇからなる貴金属群から選ばれる少なくとも１種類以上の活性金属を担持させる工程。
6th invention in this application is a manufacturing method of the exhaust gas purification catalyst characterized by including the process of following (1)-(3).
(1) A mixture containing an aluminum-containing compound, BaAl 12 O 19 , BaAl 2 O 4 having a pore size distribution peak in the second pore size region, and an organic acid, the molar ratio of aluminum to barium in the mixture Is in the range of 1: 0.02 to 1: 0.1, and the molar ratio of aluminum to organic acid is in the range of 1: 0.1 to 1: 0.5. BaAl 12 O 19 having a bimodal structure having a pore size distribution peak in the first pore size region and the second pore size region having a pore size larger than the first pore size region. Preparing the step.
(2) A step of preparing a carrier by mixing BaAl 12 O 19 having this bimodal structure and ZrO 2 .
(3) A step of supporting at least one active metal selected from a noble metal group consisting of Pt, Pd, Rh, Ru, Os, Ir, Au, and Ag on the carrier.
本出願における第７の発明は、次の［１］及び［２］の工程を含むことを特徴とする排ガス浄化触媒の製造方法である。
［１］第１の細孔径領域と、この第１の細孔径領域よりも細孔径の大きな第２の細孔径領域とに細孔径分布のピークを有するバイモーダル構造のＢａＡｌ１２Ｏ１９と、ＺｒＯ２とを含む担体を調製する工程。
［２］前工程で得られた担体に活性金属溶液を含浸させ、３５０〜５５０℃で焼成させて、前記担体に活性金属を担持する工程。
7th invention in this application is a manufacturing method of the exhaust gas purification catalyst characterized by including the process of following [1] and [2].
[1] BaAl 12 O 19 having a bimodal structure having a peak of a pore size distribution in a first pore size region and a second pore size region having a pore size larger than the first pore size region, and ZrO And 2. preparing a carrier comprising
[2] A step of impregnating the support obtained in the previous step with an active metal solution and firing at 350 to 550 ° C. to support the active metal on the support.
本出願における第８の発明は、前記バイモーダル構造のＢａＡｌ１２Ｏ１９が次の［１］〜［４］の工程を含む製造方法により得られたものであることを特徴とする排ガス浄化触媒の製造方法である。
［１］ＢａＡｌ２Ｏ４、アルミニウム含有化合物及び有機溶媒からなる分散液を湿式処理することにより第１のスラリーを調製し、該第１のスラリーを１２００〜１６００℃にて焼成することにより、第２の細孔径領域に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９を調製する工程。
［２］前工程［１］で得られたＢａＡｌ１２Ｏ１９と有機酸水溶液の混合物を湿式粉砕処理し、第２のスラリーを調製する工程。
［３］ＢａＡｌ２Ｏ４とアルミニウム含有化合物に有機酸水溶液を加え、ｐＨ３．０〜４．０の混合液を調整し、該混合液を湿式粉砕処理して第３のスラリーを調製する工程。
［４］前記第２のスラリーと第３のスラリーを混合し、７００〜１３００℃で焼成して、前記バイモーダル構造のＢａＡｌ１２Ｏ１９を調製する工程。
According to an eighth aspect of the present invention, there is provided an exhaust gas purifying catalyst characterized in that the BaAl 12 O 19 having the bimodal structure is obtained by a manufacturing method including the following steps [1] to [4]. It is a manufacturing method.
[1] A first slurry is prepared by wet-treating a dispersion composed of BaAl 2 O 4 , an aluminum-containing compound and an organic solvent, and the first slurry is fired at 1200 to 1600 ° C. A step of preparing BaAl 12 O 19 having a pore size distribution peak in the pore size region of No. 2;
[2] A step of preparing a second slurry by wet-grinding the mixture of BaAl 12 O 19 and the organic acid aqueous solution obtained in the previous step [1].
[3] A step of preparing a third slurry by adding an organic acid aqueous solution to BaAl 2 O 4 and an aluminum-containing compound, adjusting a mixed solution having a pH of 3.0 to 4.0, and wet-pulverizing the mixed solution.
[4] A step of preparing BaAl 12 O 19 having the bimodal structure by mixing the second slurry and the third slurry and baking the mixture at 700 to 1300 ° C.
本出願における第９の発明は、前記アルミニウム含有化合物は、アルミニウム酸化物、アルミニウム水酸化物、アルミニウム硝酸塩、アルミニウム塩化物、アルミニウム酢酸塩、アルミニウム炭酸塩、アルミニウム錯塩、アルミニウムアルコキシドからなるアルミニウム源群から選択される少なくとも１種類以上のアルミニウム源を含むことを特徴とする前記排ガス浄化触媒の製造方法である。
本出願における第１０の発明は、前記工程［１］で使用するアルミニウム含有化合物が結晶性アルミナからなるアルミニウム酸化物であることを特徴とする前記排ガス浄化触媒の製造方法である。
本出願における第１１の発明は、前記工程［３］で使用するアルミニウム含有化合物がアルミニウム水酸化物であることを特徴とする前記排ガス浄化触媒の製造方法である。
本出願における第１２の発明は、前記細孔径分布において、第１の細孔径領域は３．４ｎｍ以上、５．３ｎｍ以下であり、第２の細孔径領域は５４ｎｍ以上、２００ｎｍ以下であることを特徴とする前記排ガス浄化触媒の製造方法である。
According to a ninth aspect of the present application, the aluminum-containing compound is an aluminum source group comprising an aluminum oxide, an aluminum hydroxide, an aluminum nitrate, an aluminum chloride, an aluminum acetate, an aluminum carbonate, an aluminum complex, and an aluminum alkoxide. The method for producing an exhaust gas purifying catalyst according to the invention, comprising at least one selected aluminum source.
A tenth invention in the present application is the method for producing an exhaust gas purification catalyst, wherein the aluminum-containing compound used in the step [1] is an aluminum oxide made of crystalline alumina.
The eleventh invention in the present application is the method for producing an exhaust gas purification catalyst, wherein the aluminum-containing compound used in the step [3] is an aluminum hydroxide.
According to a twelfth aspect of the present application, in the pore size distribution, the first pore size region is 3.4 nm or more and 5.3 nm or less, and the second pore size region is 54 nm or more and 200 nm or less. It is a manufacturing method of the said exhaust gas purification catalyst characterized.
本発明によれば、バイモーダルな細孔径分布を有するＢａＡｌ１２Ｏ１９にＺｒＯ２を質量比で１：０．１〜１：２０の範囲で混合して得た担体に活性金属を担持することにより活性金属の活性が向上するものと推測される。そして担体の比表面積が低下したり、担体上で活性金属が凝集したりするシンタリングが進行した場合であっても、従来の排ガス浄化触媒に比べて高い触媒活性を維持することができる。この結果、シンタリングの進行に伴う活性の低下を見越して使用開始時に必要量以上の活性金属を担持するといった方策を採る必要がないか、必要があったとしてもその担持量を削減することが可能となり触媒コストの低減に貢献することができる。 According to the present invention, the active metal is supported on the support obtained by mixing ZrO 2 in a mass ratio of 1: 0.1 to 1:20 with BaAl 12 O 19 having a bimodal pore size distribution. Therefore, it is estimated that the activity of the active metal is improved. And even if the sintering in which the specific surface area of the carrier is reduced or the active metal is aggregated on the carrier proceeds, a higher catalytic activity can be maintained as compared with the conventional exhaust gas purification catalyst. As a result, in anticipation of a decrease in activity accompanying the progress of sintering, it is not necessary to take measures such as loading more than the necessary amount of active metal at the start of use, or even if necessary, the loading amount can be reduced. It becomes possible and can contribute to the reduction of the catalyst cost.
本実施の形態に係わる排ガス浄化触媒は、所定の細孔径分布を備えたＢａＡｌ１２Ｏ１９及びＺｒＯ２を含有する担体に活性金属を担持してなるものである。担体中にＢａＡｌ１２Ｏ１９及びＺｒＯ２が共存することにより、排ガス浄化触媒の高温耐久性が向上し、高温雰囲気下においても優れた触媒性能（排ガス浄化効果）を示すことができる。本発明に係わる排ガス浄化触媒について、以下に説明する。 The exhaust gas purifying catalyst according to the present embodiment is obtained by supporting an active metal on a carrier containing BaAl 12 O 19 and ZrO 2 having a predetermined pore size distribution. By coexistence of BaAl 12 O 19 and ZrO 2 in the support, the high temperature durability of the exhaust gas purification catalyst is improved, and excellent catalyst performance (exhaust gas purification effect) can be exhibited even in a high temperature atmosphere. The exhaust gas purification catalyst according to the present invention will be described below.
［排ガス浄化触媒の構成］
既述のように排ガス浄化触媒を構成する担体は、少なくともＢａＡｌ１２Ｏ１９及びＺｒＯ２を含有しており、その含有比は、担体中におけるＢａＡｌ１２Ｏ１９の質量基準の含有割合に対して、ＺｒＯ２の質量基準の含有割合の比、即ち含有量の質量比が１：０．１〜１：２０の範囲であことが好ましく、さらに好ましくは、１：０．６〜１：５．４の範囲が好適である。
[Configuration of exhaust gas purification catalyst]
As described above, the carrier constituting the exhaust gas purification catalyst contains at least BaAl 12 O 19 and ZrO 2 , and the content ratio thereof is based on the mass-based content ratio of BaAl 12 O 19 in the carrier. The ratio of the content ratio of ZrO 2 based on the mass, that is, the mass ratio of the content is preferably in the range of 1: 0.1 to 1:20, more preferably 1: 0.6 to 1: 5.4. The range of is preferable.
ＢａＡｌ１２Ｏ１９とＺｒＯ２とを含む担体に活性金属を担持してなる排ガス浄化触媒が、高温での良好な耐久性を示す作用機構の詳細については明らかではないが、ＺｒＯ２を含んだ担体に貴金属からなる活性金属を担持すると、ＺｒＯ２は当該活性金属に対して、助触媒としての役割を果たし、さらにＢａＡｌ１２Ｏ１９とＺｒＯ２とが共存することによる相互作用により、担体自体の耐久性が向上したものと推察される。 The details of the mechanism of action of the exhaust gas purifying catalyst in which an active metal is supported on a carrier containing BaAl 12 O 19 and ZrO 2 exhibit good durability at high temperatures is not clear, but the carrier containing ZrO 2 When an active metal composed of a noble metal is supported on ZrO 2 , ZrO 2 plays a role as a co-catalyst for the active metal, and further, due to the interaction between BaAl 12 O 19 and ZrO 2 , the durability of the support itself is increased. It is inferred that the performance has improved.
さらに本排ガス浄化触媒の担体のひとつであるＢａＡｌ１２Ｏ１９は、原料段階においては、細孔径分布が例えば３ｎｍ〜１０ｎｍの範囲内の、例えば第１の細孔径領域（３．４ｎｍ〜５．３ｎｍ）と、３０ｎｍ〜２００ｎｍの範囲内の、例えば第２の細孔径領域（５４ｎｍ〜２００ｎｍ）とに２つのピークを備えたバイモーダル分布を有したものである。このようなＢａＡｌ１２Ｏ１９とＺｒＯ２とを含む担体に水素化活性金属を担持してなる排ガス浄化触媒が、高温での良好な耐久性を示すことについては、バイモーダル分布を有したＢａＡｌ１２Ｏ１９において細孔径が３ｎｍ〜１０ｎｍの範囲の細孔が触媒の比表面積を大きくし、細孔径が３０ｎｍ〜２００ｎｍの範囲の細孔が活性金属のシンタリングの抑制に影響しているものと推察される。 Furthermore, BaAl 12 O 19 which is one of the supports of the exhaust gas purifying catalyst has, for example, a first pore size region (3.4 nm to 5.3 nm) having a pore size distribution in the range of 3 nm to 10 nm, for example, in the raw material stage. ) And a bimodal distribution having two peaks in the second pore diameter region (54 nm to 200 nm), for example, in the range of 30 nm to 200 nm. Regarding the fact that such an exhaust gas purifying catalyst in which a hydrogenation active metal is supported on a support containing BaAl 12 O 19 and ZrO 2 exhibits good durability at high temperatures, BaAl 12 having a bimodal distribution is used. It is presumed that the pores having a pore diameter in the range of 3 nm to 10 nm in O 19 increase the specific surface area of the catalyst, and the pores having a pore diameter in the range of 30 nm to 200 nm influence the suppression of sintering of the active metal. Is done.
本発明に係る排ガス浄化触媒は、前記担体が、さらにＢａＡｌ２Ｏ４を含むものであっても構わない。この場合、その２θ値及び相対強度で規定されるＸ線回折パターンにおいて、ＢａＡｌ１２Ｏ１９の面指数（１０７）のピーク強度に対するＢａＡｌ２Ｏ４の面指数（２０２）のピーク強度比は１：０．４〜１：１６の範囲が好ましい。本発明に係る排ガス浄化触媒は、さらにＢａＺｒＯ３を含むものであっても構わない。この場合、その２θ値及び相対強度で規定されるＸ線回折パターンにおいて、ＢａＡｌ１２Ｏ１９の面指数（１０７）のピーク強度に対するＢａＺｒＯ３の面指数（２２０）のピーク強度比は１：０．０４〜１：１．２の範囲が好ましい。 In the exhaust gas purifying catalyst according to the present invention, the carrier may further contain BaAl 2 O 4 . In this case, in the X-ray diffraction pattern defined by the 2θ value and the relative intensity, the ratio of the peak intensity of the BaAl 2 O 4 plane index (202) to the peak intensity of the BaAl 12 O 19 plane index (107) is 1: A range of 0.4 to 1:16 is preferred. The exhaust gas purification catalyst according to the present invention may further contain BaZrO 3 . In this case, in the X-ray diffraction pattern defined by the 2θ value and the relative intensity, the peak intensity ratio of the BaZrO 3 surface index (220) to the peak intensity of the BaAl 12 O 19 surface index (107) is 1: 0. A range of 04 to 1: 1.2 is preferred.
［排ガス浄化触媒の比表面積］
従来の排ガス浄化用触媒（活性金属担持後）の比表面積は、概ね１００ｍ２/ｇ程度であり、触媒として使用した場合は、経時的に比表面積が低下し、触媒活性が低下する傾向があった。これに対して本実施の形態に係る排ガス浄化触媒の比表面積については、格別に限定されるものではないが、例えば、０．１ｍ２/ｇ〜１１０ｍ２/ｇの範囲で使用可能である。
[Specific surface area of exhaust gas purification catalyst]
The specific surface area of the conventional exhaust gas purifying catalyst (after supporting the active metal) is about 100 m 2 / g, and when used as a catalyst, the specific surface area tends to decrease with time and the catalytic activity tends to decrease. It was. The specific surface area of the exhaust gas purifying catalyst according to the present embodiment, on the other hand, but are not particularly limited, for example, can be used in the range of 0.1m 2 / g~110m 2 / g.
［活性金属］
前記活性金属としては、Ｐｔ（白金）、Ｐｄ（パラジウム）、Ｒｈ（ロジウム）、Ｒｕ（ルテニウム）、Ｏｓ（オスミウム）、Ｉｒ（イリジウム）、Ａｕ（金）及びＡｇ（銀）からなる貴金属群から選ばれる少なくとも１種類以上の活性金属が使用される。前記排ガス浄化触媒に占める活性金属の割合については、０．０１質量％以上、２．０質量％以下の範囲が好ましい。活性金属の割合が０．０１質量％未満の場合には、実用的な触媒性能が得られない場合がある。また、活性金属の割合が２．０質量％を超える場合は、触媒性能を向上させる効果が飽和する傾向が強くなるので、必ずしも必要とはされない。排ガス浄化触媒に占める活性金属の割合については、さらに好適には０．１〜１．０質量％の範囲が推奨される。
[Active metal]
Examples of the active metal include a noble metal group consisting of Pt (platinum), Pd (palladium), Rh (rhodium), Ru (ruthenium), Os (osmium), Ir (iridium), Au (gold), and Ag (silver). At least one active metal selected is used. About the ratio of the active metal to the said exhaust gas purification catalyst, the range of 0.01 mass% or more and 2.0 mass% or less is preferable. When the ratio of the active metal is less than 0.01% by mass, practical catalyst performance may not be obtained. Moreover, when the ratio of an active metal exceeds 2.0 mass%, since the tendency to saturate the effect which improves catalyst performance becomes strong, it is not necessarily required. About the ratio of the active metal which occupies for an exhaust gas purification catalyst, the range of 0.1-1.0 mass% is further recommended suitably.
本発明に係る排ガス浄化触媒には、前記活性金属に加えて、例えば遷移金属元素あるいは希土類元素等の元素、例えばＭｎ（マンガン）、Ｆｅ（鉄）、Ｃｏ（コバルト）、Ｎｉ（ニッケル）、Ｃｕ（銅）、Ｙ（イットリウム）、Ｚｒ（ジルコニウム）、Ｌａ（ランタン）、Ｃｅ（セリウム）、Ｐｒ（プラセオジム）などから選択される１以上の元素を添加剤として担持しても構わない。これらの添加剤は、活性向上の目的で必要に応じて適宜添加される。 The exhaust gas purifying catalyst according to the present invention includes, in addition to the active metal, elements such as transition metal elements or rare earth elements, such as Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Cu One or more elements selected from (copper), Y (yttrium), Zr (zirconium), La (lanthanum), Ce (cerium), Pr (praseodymium) and the like may be supported as an additive. These additives are appropriately added as needed for the purpose of improving the activity.
［排ガス浄化触媒の製造方法］
本実施の形態に係わる排ガス浄化触媒は、例えばアルミニウム含有化合物、細孔径３０〜２００ｎｍの範囲、好ましくは第２の細孔径領域に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９、ＢａＡｌ２Ｏ４及び有機酸を含む混合物を７００℃〜１３００℃の範囲で焼成し得られたＢａＡｌ１２Ｏ１９をＺｒＯ２と混合して担体を形成し、この担体に活性金属を担持させることなどにより得ることができる。以下、本実施の形態に係る排ガス浄化触媒の具体的な製造方法の一例を示すが、当該排ガス浄化触媒の製造方法はこれに限定されるものではない。
[Method for producing exhaust gas purification catalyst]
The exhaust gas purifying catalyst according to the present embodiment includes, for example, an aluminum-containing compound, BaAl 12 O 19 , BaAl 2 O 4 having a pore diameter distribution peak in the pore diameter range of 30 to 200 nm, preferably in the second pore diameter region, and BaAl 12 O 19 obtained by firing a mixture containing an organic acid at a temperature in the range of 700 ° C. to 1300 ° C. is mixed with ZrO 2 to form a carrier, and this carrier can be obtained by loading an active metal on the carrier. . Hereinafter, although an example of the concrete manufacturing method of the exhaust gas purification catalyst which concerns on this Embodiment is shown, the manufacturing method of the said exhaust gas purification catalyst is not limited to this.
［担体の製造工程］
ＢａＡｌ１２Ｏ１９は、例えばアルミニウム含有化合物とＢａＡｌ２Ｏ４とを混合してから焼成することなどにより得ることができる。
前記アルミニウム含有化合物については、通常は、アルミニウムの酸化物、水酸化物、硝酸塩、酢酸塩、炭酸塩、錯塩及びアルコキシドから選ばれる少なくとも１種類のアルミニウム含有化合物から選ばれる。前記アルミニウム含有化合物の具体例としては、アルミニウム酸化物、アルミニウム水酸化物、アルミニウム硝酸塩、アルミニウム塩化物、アルミニウム酢酸塩、アルミニウム炭酸塩、アルミニウム錯塩、アルミニウムアルコキシドから選ばれるアルミニウム含有化合物が好適に使用される。
[Manufacturing process of carrier]
BaAl 12 O 19 can be obtained, for example, by mixing an aluminum-containing compound and BaAl 2 O 4 and then firing.
The aluminum-containing compound is usually selected from at least one aluminum-containing compound selected from aluminum oxide, hydroxide, nitrate, acetate, carbonate, complex salt and alkoxide. As specific examples of the aluminum-containing compound, an aluminum-containing compound selected from aluminum oxide, aluminum hydroxide, aluminum nitrate, aluminum chloride, aluminum acetate, aluminum carbonate, aluminum complex, and aluminum alkoxide is preferably used. The
特に細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９は、例えば、次の工程により調製することができる。
（第１工程）
ＢａＡｌ２Ｏ４、アルミニウム含有化合物及びメチルアルコールなどの有機溶媒からなる分散液を湿式粉砕処理することにより第１のスラリーを調製し、該第１のスラリーを１２００〜１８００℃にて焼成することにより、細孔径３０〜２００ｎｍの範囲に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９を調製する。アルミニウム含有化合物には、例えば結晶性アルミナなどのアルミニウム酸化物が好適に使用される。
（第２工程）
第１工程で得られたＢａＡｌ１２Ｏ１９と有機酸水溶液の混合物を湿式粉砕処理し、第２のスラリーを調製する。
（第３工程）
ＢａＡｌ２Ｏ４とアルミニウム含有化合物に有機酸水溶液を加え、ｐＨ３．０〜４．０の混合液を調製し、該混合液を湿式粉砕処理して第３のスラリーを調製する。アルミニウム含有化合物には例えばアルミニウム水酸化物が好適に使用される。
（第４工程）
第２のスラリーと第３のスラリーを混合し、７００〜１３００℃で焼成して、ＢａＡｌ１２Ｏ１９を調製する。
In particular, BaAl 12 O 19 having a pore size distribution of bimodal structure can be prepared, for example, by the following steps.
(First step)
By preparing a first slurry by wet-grinding a dispersion composed of an organic solvent such as BaAl 2 O 4 , an aluminum-containing compound and methyl alcohol, and firing the first slurry at 1200 to 1800 ° C. BaAl 12 O 19 having a pore size distribution peak in the pore size range of 30 to 200 nm is prepared. As the aluminum-containing compound, for example, an aluminum oxide such as crystalline alumina is preferably used.
(Second step)
The mixture of BaAl 12 O 19 and the organic acid aqueous solution obtained in the first step is wet-pulverized to prepare a second slurry.
(Third step)
An organic acid aqueous solution is added to BaAl 2 O 4 and an aluminum-containing compound to prepare a mixed solution having a pH of 3.0 to 4.0, and the mixed solution is subjected to wet pulverization to prepare a third slurry. For example, aluminum hydroxide is preferably used as the aluminum-containing compound.
(4th process)
The second slurry and the third slurry are mixed, and fired at 700-1300 ° C., to prepare a BaAl 12 O 19.
このような製造方法において第１工程は、例えばアルミニウム含有化合物とＢａＡｌ２Ｏ４とに所定量のメチルアルコールを加え、例えば湿式粉砕処理し、得られたスラリーを焼成すると、数十〜２００ｎｍ付近に細孔径分布のピークを持つＢａＡｌ１２Ｏ１９が得られる現象を利用している。また、第３工程及び第４工程は、アルミニウム含有化合物とＢａＡｌ２Ｏ４とに所定量の有機酸水溶液を加え、例えば湿式粉砕処理し、得られたスラリーを焼成すると、数ｎｍ〜１０ｎｍ付近に細孔径分布のピークを持つＢａＡｌ１２Ｏ１９が得られる現象を使用したものである。 In such a production method, for example, the first step is to add a predetermined amount of methyl alcohol to, for example, an aluminum-containing compound and BaAl 2 O 4 , for example, wet pulverization treatment, and firing the resulting slurry, the vicinity of several tens to 200 nm The phenomenon that BaAl 12 O 19 having a peak of pore size distribution is obtained is used. Further, in the third step and the fourth step, when a predetermined amount of an organic acid aqueous solution is added to the aluminum-containing compound and BaAl 2 O 4 , for example, wet pulverization treatment is performed, and the obtained slurry is fired, This is a phenomenon in which BaAl 12 O 19 having a pore size distribution peak is obtained.
例えばメチルアルコール、アルミニウム含有化合物及びＢａＡｌ２Ｏ４との混合物から細孔径３０〜２００ｎｍの範囲に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９を予め調製する。次いで、有機酸水溶液、アルミニウム含有化合物及びＢａＡｌ２Ｏ４との混合物に、細孔径３０〜２００ｎｍの範囲に細孔径分布のピークを有する上述のＢａＡｌ１２Ｏ１９を混合して焼成を行うことにより、バイモーダル構造であり、細孔径分布において細孔径３ｎｍ〜１０ｎｍの範囲内と３０ｎｍ〜２００ｎｍの範囲内とに各々細孔径のピークを有するＢａＡｌ１２Ｏ１９を得ることができる。 For example, BaAl 12 O 19 having a pore size distribution peak in a pore size range of 30 to 200 nm is prepared in advance from a mixture of methyl alcohol, an aluminum-containing compound, and BaAl 2 O 4 . Next, the mixture of the aqueous organic acid solution, the aluminum-containing compound and BaAl 2 O 4 is mixed with the aforementioned BaAl 12 O 19 having a pore size distribution peak in the pore size range of 30 to 200 nm, followed by firing. BaAl 12 O 19 that has a bimodal structure and has pore diameter peaks in the pore diameter distribution in the range of 3 nm to 10 nm and in the range of 30 nm to 200 nm can be obtained.
［第１工程］
アルミニウムとＢａＡｌ２Ｏ４との混合比は、焼成後の生成物がＢａＡｌ１２Ｏ１９となる混合比を予め求めておき、その混合比に基づいて原料が混合される。ＢａＡｌ１２Ｏ１９を得る場合には、混合物中のアルミニウムに対するバリウムのモル比は例えば１：０．０２〜１：０．１（化学量論比１：０．０８３）の範囲に調整して混合することが好ましい。また、焼成によってアルミニウムとＢａＡｌ２Ｏ４との反応を進行しやすくして効率よくＢａＡｌ１２Ｏ１９を生成することができるように、アルミニウムとＢａＡｌ２Ｏ４との混合物の平均粒子径を例えば０．０１μｍ〜０．２μｍの範囲となるように調製するとよい。
[First step]
As for the mixing ratio of aluminum and BaAl 2 O 4 , a mixing ratio in which the product after firing becomes BaAl 12 O 19 is obtained in advance, and the raw materials are mixed based on the mixing ratio. When obtaining BaAl 12 O 19 , the molar ratio of barium to aluminum in the mixture is adjusted to a range of, for example, 1: 0.02 to 1: 0.1 (stoichiometric ratio 1: 0.083) and mixed. It is preferable to do. Further, the average particle size of the mixture of aluminum and BaAl 2 O 4 is set to 0, for example, so that the reaction between aluminum and BaAl 2 O 4 can easily proceed by firing and BaAl 12 O 19 can be efficiently generated. It is good to prepare so that it may become the range of 0.01 micrometer-0.2 micrometer.
メチルアルコールの使用量については、アルミニウム含有化合物とＢａＡｌ２Ｏ４の合計質量（１００質量部）に対して、１００〜１００００質量部の範囲が好ましい。１００質量部未満では、湿式粉砕処理に適さない。１００００質量部を超えると、効率的に粉砕が行えない問題がある。メチルアルコールのより好適な使用量範囲としては、１８０〜３００質量部の範囲が推奨される。 The amount of methyl alcohol, based on the total weight of the aluminum-containing compound and BaAl 2 O 4 (100 parts by mass) is preferably within a range of 100 to 10,000 parts by weight. If it is less than 100 parts by mass, it is not suitable for wet grinding. When the amount exceeds 10,000 parts by mass, there is a problem that grinding cannot be performed efficiently. As a more preferable use amount range of methyl alcohol, a range of 180 to 300 parts by mass is recommended.
ここでアルミニウム含有化合物とＢａＡｌ２Ｏ４は、メチルアルコールに溶解しにくいため、湿式粉砕処理により概ね０．１〜２．０μｍの粒子となりやすく、この結果、焼成により細孔径３０〜２００ｎｍの範囲に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９を得やすくなる。湿式粉砕処理に用いることのできる有機溶媒は、既述のメチルアルコールに限定されるものではなく、例えばエチルアルコール、２−プロパノン、アセトアルデヒドなどの公知の有機溶媒を用いることもできる。 Here, since the aluminum-containing compound and BaAl 2 O 4 are difficult to dissolve in methyl alcohol, they are likely to become particles of about 0.1 to 2.0 μm by wet pulverization treatment, and as a result, the pore diameter is in the range of 30 to 200 nm by firing. It becomes easy to obtain BaAl 12 O 19 having a pore size distribution peak. The organic solvent that can be used for the wet pulverization treatment is not limited to the above-described methyl alcohol, and known organic solvents such as ethyl alcohol, 2-propanone, and acetaldehyde can also be used.
アルミニウム化合物、ＢａＡｌ２Ｏ４及びメチルアルコールは、湿式粉砕処理により第１のスラリーとし、１２００〜１８００℃で焼成することにより３０〜２００ｎｍの範囲に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９を得ることができる。湿式粉砕の処理条件については、例えばボールミルにて、７０〜１２０ｒｐｍで２０〜４０時間処理して、平均粒子径０．０１〜０．２μｍの粒子とすることが好ましい。 The aluminum compound, BaAl 2 O 4 and methyl alcohol are made into a first slurry by wet pulverization treatment and fired at 1200 to 1800 ° C. to obtain BaAl 12 O 19 having a pore size distribution peak in the range of 30 to 200 nm. be able to. About the processing conditions of wet-grinding, it is preferable to process with a ball mill at 70 to 120 rpm for 20 to 40 hours to obtain particles having an average particle diameter of 0.01 to 0.2 μm.
［第２工程］
第１工程で得られた細孔径３０〜２００ｎｍの範囲に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９に、有機酸水溶液を加え、湿式粉砕処理を行いスラリー化する。有機酸水溶液の使用量は、ＢａＡｌ１２Ｏ１９が１００質量部に対して、１〜３５質量部の範囲が好ましい。湿式粉砕の処理条件については、例えばボールミルにて７０〜１２０ｒｐｍで、０．５〜２時間処理して、平均粒子径０．５〜２．５μｍの粒子とすることが好ましい。ここで得られた第２のスラリーを次の第３工程で得られる第３のスラリーと混合する。第２のスラリーのｐＨは特段の限定はないが、例えば第３のスラリーと混合した後の混合スラリーのｐＨが大きく変わらないように、第３のスラリーと同程度のｐＨとする場合などが考えられる。
[Second step]
An organic acid aqueous solution is added to BaAl 12 O 19 having a pore size distribution peak in the pore size range of 30 to 200 nm obtained in the first step, and a wet pulverization treatment is performed to form a slurry. The amount of the organic acid aqueous solution used is preferably in the range of 1 to 35 parts by mass with respect to 100 parts by mass of BaAl 12 O 19 . About the processing conditions of wet-grinding, it is preferable to process by a ball mill at 70-120 rpm for 0.5-2 hours, and to make it the particle | grain of an average particle diameter of 0.5-2.5 micrometers. The second slurry obtained here is mixed with the third slurry obtained in the next third step. The pH of the second slurry is not particularly limited. For example, there is a case where the pH of the mixed slurry after mixing with the third slurry is set to the same level as that of the third slurry so that the pH of the mixed slurry does not change greatly. It is done.
［第３工程］
アルミニウムとＢａＡｌ２Ｏ４との混合比は、焼成後の生成物がＢａＡｌ１２Ｏ１９となる混合比を予め求めておき、その混合比に基づいて原料が混合される。ＢａＡｌ１２Ｏ１９を得る場合には、混合物のアルミニウムに対するバリウムのモル比は例えば１：０．０２〜１：０．１（化学量論比１：０．０８３）の範囲に調整して混合することが好ましい。また、焼成によってアルミニウムとＢａＡｌ２Ｏ４との反応を進行しやすくして効率よくＢａＡｌ１２Ｏ１９を生成することができるように、アルミニウムとＢａＡｌ２Ｏ４との混合物の平均粒子径を例えば０．０１μｍ〜０．２μｍの範囲となるように調製するとよい。
[Third step]
As for the mixing ratio of aluminum and BaAl 2 O 4 , a mixing ratio in which the product after firing becomes BaAl 12 O 19 is obtained in advance, and the raw materials are mixed based on the mixing ratio. When obtaining BaAl 12 O 19 , the molar ratio of barium to aluminum in the mixture is adjusted to a range of, for example, 1: 0.02 to 1: 0.1 (stoichiometric ratio 1: 0.083) and mixed. It is preferable. Further, the average particle size of the mixture of aluminum and BaAl 2 O 4 is set to 0, for example, so that the reaction between aluminum and BaAl 2 O 4 can easily proceed by firing and BaAl 12 O 19 can be efficiently generated. It is good to prepare so that it may become the range of 0.01 micrometer-0.2 micrometer.
有機酸水溶液の使用量については、アルミニウム含有化合物とＢａＡｌ２Ｏ４の合計量（１００質量部）に対して、５０〜８０質量部の範囲が好ましい。５０質量部未満では、分解活性の効果が低減する傾向にある。８０質量部を超えると効果が飽和する。有機酸水溶液のより好適な使用量範囲としては６０〜６５質量部の範囲が推奨される。 The amount of the aqueous organic acid solution, the total amount of aluminum-containing compound and BaAl 2 O 4 with respect to (100 parts by weight), preferably in the range of 50 to 80 parts by weight. If it is less than 50 parts by mass, the effect of decomposition activity tends to be reduced. If it exceeds 80 parts by mass, the effect is saturated. As a more preferable range of use amount of the organic acid aqueous solution, a range of 60 to 65 parts by mass is recommended.
ここでアルミニウム含有化合物とＢａＡｌ２Ｏ４は、有機酸水溶液を加えｐＨを２．０〜６．０に低下させることにより、湿式粉砕処理にて概ね０．０１〜０．１μｍの粒子となりやすい。この結果、焼成により細孔径１〜１０ｎｍの範囲に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９が得やすくなる。第３のスラリーのより好適なｐＨは３．０〜４．０である。 Here, the aluminum-containing compound and BaAl 2 O 4 tend to become particles of about 0.01 to 0.1 μm by wet pulverization treatment by adding an organic acid aqueous solution and lowering the pH to 2.0 to 6.0. As a result, BaAl 12 O 19 having a pore size distribution peak in the pore size range of 1 to 10 nm is easily obtained by firing. A more preferable pH of the third slurry is 3.0 to 4.0.
有機酸水溶液としては、公知のものを使用することができる。具体的には、グリコール酸、ギ酸、酢酸、シュウ酸、クエン酸などを挙げることができるが、これらに限定されるものではない。
アルミニウム含有化合物、ＢａＡｌ２Ｏ４及び有機酸水溶液は、湿式粉砕処理により第３のスラリーとする。湿式粉砕の処理条件については、例えばボールミルにて、７０〜１２０ｒｐｍで、１５〜２０時間処理して、平均粒子径０．０５〜０５μｍの粒子とすることが好ましい。
Known organic acid aqueous solutions can be used. Specific examples include glycolic acid, formic acid, acetic acid, oxalic acid, and citric acid, but are not limited thereto.
The aluminum-containing compound, BaAl 2 O 4 and the organic acid aqueous solution are made into a third slurry by wet pulverization. About the processing conditions of wet grinding, it is preferable to process with a ball mill at 70 to 120 rpm for 15 to 20 hours to obtain particles having an average particle size of 0.05 to 05 μm.
［第４工程］
第２のスラリーと第３のスラリーとを混合してなる混合物を、７００〜１３００℃で焼成することにより、細孔径分布がバイモーダル構造であり、細孔径１〜１０ｎｍの範囲と３０〜２００ｎｍの範囲とに細孔を顕著に有するＢａＡｌ１２Ｏ１９を得ることができる。また、細孔径の大きなＢａＡｌ１２Ｏ１９に細孔径の小さなＢａＡｌ１２Ｏ１９を成長させることにより、これらピークの異なる細孔径を共存させ、バイモーダル構造が得られやすくなる。
[Fourth step]
By baking the mixture obtained by mixing the second slurry and the third slurry at 700 to 1300 ° C., the pore size distribution has a bimodal structure, and the pore size range of 1 to 10 nm and the range of 30 to 200 nm. BaAl 12 O 19 having remarkably fine pores in the range can be obtained. Further, by growing BaAl 12 O 19 having a small pore diameter on BaAl 12 O 19 having a large pore diameter, pore diameters having different peaks can coexist and a bimodal structure can be easily obtained.
ＢａＡｌ１２Ｏ１９の焼成は、上述の各混合物を必要に応じて乾燥させ、その後、例えば空気中で７００℃〜１３００℃の範囲の温度に加熱することにより行われる。焼成温度が７００℃より低い場合には、ＢａＡｌ１２Ｏ１９が形成されにくく十分な触媒活性を得ることができず、また、調製時に混合している有機酸が完全に燃焼しない可能性がある。また、１３００℃を超える温度で焼成を行う場合には、耐熱性の高い特殊な炉材を用いた焼成炉が必要となり経済性が低くなるおそれがある。 BaAl 12 O 19 is fired by drying each of the above-described mixtures as necessary, and then heating the mixture to a temperature in the range of 700 ° C. to 1300 ° C., for example, in air. When the calcination temperature is lower than 700 ° C., BaAl 12 O 19 is hardly formed and sufficient catalytic activity cannot be obtained, and the organic acid mixed during preparation may not burn completely. Moreover, when baking at the temperature exceeding 1300 degreeC, there exists a possibility that the baking furnace using a special furnace material with high heat resistance may be needed and economy may become low.
このようにして得られたバイモーダル構造のＢａＡｌ１２Ｏ１９にＺｒＯ２を例えば質量比で１：０．１〜１：２０の割合にて混合することにより、バイモーダル構造のＢａＡｌ１２Ｏ１９と、ＺｒＯ２とからなる本実施の形態に係る排ガス浄化触媒の担体を得ることができる。
そして、後述の実施例中に示すように、バイモーダル構造のＢａＡｌ１２Ｏ１９を含む担体は、バイモーダル構造を備えていないＢａＡｌ１２Ｏ１９とＺｒＯ２とを混合して得られた担体と比較して、より高い高温耐久性を示すことが分かっている。
Such a ZrO 2, for example a mass ratio BaAl 12 O 19 obtained bimodal structure in the 1: 0.1 to 1: by mixing at 20 ratio, and BaAl 12 O 19 bimodal structure , ZrO 2 and the exhaust gas purifying catalyst carrier according to the present embodiment can be obtained.
As shown in Examples below, the carrier comprising a BaAl 12 O 19 bimodal structure, a support obtained by mixing the BaAl 12 O 19 and ZrO 2 without a bimodal structure comparison Thus, it has been found to exhibit higher high temperature durability.
［活性金属の担持工程］
上述の手法により得られた担体に、Ｐｔ、Ｐｄ、Ｒｈ、Ｒｕ、Ｏｓ、Ｉｒ、ＡｕまたはＡｇからなる貴金属群から選ばれる活性金属を担持することにより、本実施の形態の排ガス浄化触媒を得ることができる。活性金属の担持方法については、格別に限定されるものではないが、通常は固相混合法、液相混合法、共沈法、含浸法、逆ミセル法などの各種の担持法が適応される。
[Supporting process of active metal]
By supporting an active metal selected from the group of precious metals consisting of Pt, Pd, Rh, Ru, Os, Ir, Au or Ag on the support obtained by the above-described method, the exhaust gas purification catalyst of the present embodiment is obtained. be able to. The active metal loading method is not particularly limited, but various loading methods such as a solid phase mixing method, a liquid phase mixing method, a coprecipitation method, an impregnation method, and a reverse micelle method are usually applied. .
例えば、含浸法による場合には、前記活性金属の単体を溶解した溶液、または当該活性金属を含む化合物（例えば、金属塩、金属酸化物、金属水酸化物）の溶液に、前記工程で調製した担体を含浸させ、溶媒を蒸発乾固させた後、大気中または不活性雰囲気中にて温度３００℃〜５００℃で焼成することにより、排ガス浄化触媒を調製する。前記焼成時間については、通常は１〜５時間の範囲で行われる。なお、焼成に先立って、温度９０〜１５０℃で１〜１２時間の範囲で乾燥処理を行っても構わない。 For example, in the case of the impregnation method, the solution is prepared in the above step in a solution in which the simple substance of the active metal is dissolved or a compound containing the active metal (for example, metal salt, metal oxide, metal hydroxide). After impregnating the support and evaporating the solvent to dryness, the exhaust gas purification catalyst is prepared by firing at a temperature of 300 ° C. to 500 ° C. in the air or in an inert atmosphere. About the said baking time, it is normally performed in the range of 1 to 5 hours. In addition, you may perform a drying process in the range of 1 to 12 hours at the temperature of 90-150 degreeC prior to baking.
活性金属の単体又は活性金属を含む化合物の溶液の溶媒については、水または有機溶媒が使用される。ここで、有機溶媒としては、担体、活性金属の単体金属又は活性金属を含む化合物と反応性のないものであれば利用することができる。 Water or an organic solvent is used for the solvent of the active metal simple substance or the solution of the compound containing the active metal. Here, any organic solvent can be used as long as it is not reactive with a carrier, a single metal of an active metal, or a compound containing an active metal.
排ガス浄化触媒における前記活性金属の担持量、担持した活性金属の粒子径については、活性金属の担持方法によっても異なるが、通常は前記活性金属の溶液（金属単体の溶液、活性金属を含む化合物の溶液）に含まれる金属成分の濃度を調節することにより制御することができる。金属濃度としては、通常は０．１〜１０重量％の範囲が選択され、例えば当該溶液中に含まれる活性金属と、担体との質量比に基づいて、例えば０．０１重量％以上、２．０重量％以下の活性金属が担持された排ガス浄化触媒を調製することができる。 The amount of the active metal supported in the exhaust gas purification catalyst and the particle diameter of the supported active metal differ depending on the method of supporting the active metal. Usually, however, the solution of the active metal (a solution of a single metal or a compound containing an active metal). It can be controlled by adjusting the concentration of the metal component contained in the solution. As the metal concentration, a range of 0.1 to 10% by weight is usually selected. An exhaust gas purifying catalyst carrying 0% by weight or less of active metal can be prepared.
ここで排ガス浄化触媒に担持される活性金属の粒子径は、担体の組成によっても影響を受ける場合がある。したがって、排ガス浄化触媒の設計にあたっては、事前に担体組成、活性金属の種類、活性金属を含む化合物の溶液濃度などと、粒子径との関係について、実験により検量線を作成し、排ガス浄化触媒上に担持される活性金属が所望の粒子径となるように調製するとよい。 Here, the particle diameter of the active metal supported on the exhaust gas purification catalyst may be influenced by the composition of the carrier. Therefore, when designing an exhaust gas purification catalyst, a calibration curve is created in advance for the relationship between the carrier composition, the type of active metal, the solution concentration of the compound containing the active metal, etc. It is preferable to prepare the active metal supported on the catalyst so as to have a desired particle size.
［モノリス触媒］
以上に例示した手法により製造された排ガス浄化触媒を、例えばウォッシュコート法などによって例えばセラミック製のハニカム基体にコーティングすることによりモノリス触媒が得られる。ウォッシュコート法は、当該排ガス浄化触媒を均一に分散させ、粘度を調整したスラリー中に前記ハニカム基体を浸漬してから引き上げ、これを乾燥させることにより触媒をコーティングする手法である。
[Monolith catalyst]
A monolithic catalyst can be obtained by coating the exhaust gas purifying catalyst manufactured by the method exemplified above on, for example, a ceramic honeycomb substrate by, for example, a wash coat method. The wash coating method is a method of coating the catalyst by uniformly dispersing the exhaust gas purification catalyst, immersing the honeycomb substrate in a slurry whose viscosity is adjusted, and then drying the honeycomb substrate.
なお、自動車などに搭載する排ガス浄化触媒の形状はモノリス触媒に限定されるものではなく、例えば打錠や転動により、触媒をペレット状に形成してもよい。この場合は、例えばペレット触媒が充填された反応器内に排ガスを通流させることなどにより、排ガスを浄化することができる。 Note that the shape of the exhaust gas purification catalyst mounted on an automobile or the like is not limited to the monolith catalyst, and the catalyst may be formed into a pellet by, for example, tableting or rolling. In this case, the exhaust gas can be purified, for example, by passing the exhaust gas through a reactor filled with a pellet catalyst.
以上に述べた手法によって得られた排ガス浄化触媒は、後述の実験結果に示すように、従来の排ガス浄化触媒（比表面積１００ｍ２／ｇ以上）と比較して例えば比表面積が０．１ｍ２／ｇ〜１００ｍ２／ｇ程度と小さく、且つ活性金属の担持量が少ないにもかかわらず、排ガス中の窒素酸化物や一酸化窒素、炭化水素を分解して排ガスを浄化する高い触媒活性を備えている。さらにこの排ガス浄化触媒は、高温の排ガスと長期間接触させてもその触媒活性が低下しにくいといった特徴も備えている。
Exhaust gas purifying catalyst obtained by the procedure described above, as shown in the experimental results described later, the conventional exhaust gas purifying catalyst (specific surface area 100
本実施の形態に係る排ガス浄化触媒によれば、ＢａＡｌ１２Ｏ１９とＺｒＯ２とを含有し、バイモーダルな細孔径分布を有する担体に活性金属を担持することにより活性金属の活性が向上するものと推測され、担体の比表面積が低下したり、担体上で活性金属が凝集したりするシンタリングが進行した場合であっても、従来の排ガス浄化触媒に比べて高い触媒活性を維持することができる。この結果、シンタリングの進行に伴う活性の低下を見越して使用開始時に必要量以上の活性金属を担持するといった方策を採る必要がないか、必要があったとしてもその担持量を削減することが可能となり触媒コストの低減に貢献することができる。 According to the exhaust gas purification catalyst according to the present embodiment, the activity of the active metal is improved by supporting the active metal on the support containing BaAl 12 O 19 and ZrO 2 and having a bimodal pore size distribution. It is estimated that even if the sintering progresses such that the specific surface area of the support decreases or the active metal aggregates on the support, high catalytic activity can be maintained compared to conventional exhaust gas purification catalysts. it can. As a result, in anticipation of a decrease in activity accompanying the progress of sintering, it is not necessary to take measures such as loading more than the necessary amount of active metal at the start of use, or even if necessary, the loading amount can be reduced. It becomes possible and can contribute to the reduction of the catalyst cost.
［１］Ｘ線回折測定（ＸＲＤ）
Ｘ線回折測定は株式会社リガク製MultiFlexを用いた。測定はＸ線源をＣｕ、波長１５．４０５６ｎｍ）、管電圧を４０ｋＶ、管電流を２０ｍＡ、データ範囲を２θ=１０〜８０Ｄｅｇ．、サンプリング間隔を０．０２Ｄｅｇ．、スキャン速度を０．３Ｄｅｇ．/秒、発散スリットを１．０Ｄｅｇ．、散乱スリットを１．０Ｄｅｇ．、発光スリットを０．３ｍｍの条件で行った。
[1] X-ray diffraction measurement (XRD)
For X-ray diffraction measurement, MultiFlex manufactured by Rigaku Corporation was used. The X-ray source is Cu, the wavelength is 15.4056 nm), the tube voltage is 40 kV, the tube current is 20 mA, and the data range is 2θ = 10 to 80 Degg. The sampling interval is 0.02 Deg. The scan speed is 0.3 Deg. / Second, the divergence slit is 1.0 Deg. The scattering slit is 1.0 Degg. The light emitting slit was performed under the condition of 0.3 mm.
［２］比表面積測定
比表面積はＢＥＴ法によって測定した。測定はユアサアイオニクス株式会社製マルチソーブ１２型を用い、サンプルの前処理は２５０℃で４０分間行った。
[2] Specific surface area measurement
The specific surface area was measured by the BET method. The measurement was performed using Yuasa Ionics Co., Ltd. multisorb type 12 and the sample was pretreated at 250 ° C. for 40 minutes.
［３］ＣＯパルス法による担持微粒子の平均粒子径測定
貴金属の担持微粒子の平均粒子径測定は、自作の流通式の装置を用いた。測定は日本触媒学会発行の触媒（１９８６年、page２８-４１）に記載されているＣＯパルス法によって求めた。
[3] Measurement of average particle size of supported fine particles by CO pulse method
A self-made flow-type apparatus was used to measure the average particle size of the noble metal supported fine particles. The measurement was performed by the CO pulse method described in the catalyst (1986, pages 28-41) published by the Japan Society for Catalysis.
［４］触媒活性試験
実施例及び比較例で調製した各排ガス浄化触媒を高温雰囲気下で保持する高温耐久処理を行い、処理前後での触媒の活性を調べた。使用したモノリス触媒の作製方法とライトオフ温度の測定方法は次の通り。
[4] Catalytic activity test
Each exhaust gas purification catalyst prepared in the examples and comparative examples was subjected to a high temperature durability treatment in which it was maintained in a high temperature atmosphere, and the activity of the catalyst before and after the treatment was examined. The production method of the monolith catalyst used and the measurement method of the light-off temperature are as follows.
（１）モノリス触媒の作製方法
実施例及び比較例で調製した排ガス浄化触媒を水に分散して、排ガス浄化用触媒を含有するスラリー（固形分３０質量％）を得た。そして、コージェライト製のセラミックハニカム基体（体積５．３ｃｍ３、４００cells／inch２）を前記スラリー中に浸漬し、引き上げる方法（ウォッシュコート法）により、コート密度が１００ｇ／Ｌとなるようにコートして、基体上に均一な触媒層を形成させ、サンプル用のモノリス触媒を得た。
(1) Production Method of Monolith Catalyst The exhaust gas purification catalyst prepared in the examples and comparative examples was dispersed in water to obtain a slurry (
（２）ライトオフ温度の測定方法
各モノリス触媒を８００℃に加熱した大気雰囲気中で２４時間保持する高温耐久処理を行い、当該処理の前後にてモデルガスを処理し、各触媒の耐久性能を調べた。
モデルガスの処理実験にあたっては、各モノリス触媒を常圧流通式の試験装置に装填し、図１に示す組成のモデルガス（理論空気比１４．７）を空間速度５００００ｈ−１で通流した。試験装置の触媒のホルダーにはヒータが設けられており、このヒータによりモノリス触媒の温度を１５０℃から６５０℃へと漸次上昇させ、モデルガス中のプロピレン（Ｃ３Ｈ６：以下ＨＣという）の浄化率（（モノリス触媒入口のＨＣ濃度−モノリス触媒出口のＨＣ濃度）×１００／モノリス触媒入口のＨＣ濃度［％］）が５０％に達したときの温度をライトオフ温度（以下、Ｔ５０温度と記す）と定義して、このライトオフ温度を比較することにより評価を行った。
(2) Measuring method of light-off temperature Each monolith catalyst is subjected to high-temperature durability treatment for 24 hours in an air atmosphere heated to 800 ° C., model gas is treated before and after the treatment, and the durability performance of each catalyst is determined. Examined.
In the model gas treatment experiment, each monolith catalyst was loaded into an atmospheric pressure flow type test apparatus, and the model gas (theoretical air ratio 14.7) having the composition shown in FIG. 1 was passed at a space velocity of 50000 h −1 . A heater is provided in the catalyst holder of the test apparatus, and the temperature of the monolith catalyst is gradually increased from 150 ° C. to 650 ° C. by this heater, and propylene (C 3 H 6 : hereinafter referred to as HC) in the model gas is increased. The temperature at which the purification rate ((HC concentration at the monolith catalyst inlet−HC concentration at the monolith catalyst outlet) × 100 / HC concentration [%] at the monolith catalyst inlet) reaches 50% is defined as the light-off temperature (hereinafter referred to as T50 temperature). Evaluation was performed by comparing the light-off temperature.
［５］細孔径分布がバイモーダル構造の担体の調製方法
（１）細孔径が３０ｎｍ〜２００ｎｍの範囲に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９の調製
外径１２０φ、内容積９００ｃｍ３の磁製ボールミルにＢａＡｌ２Ｏ４（株式会社高純度化学研究所、純度９９．９％）１６．７ｇ、α-アルミナ（日本軽金属株式会社製）３３．３ｇ、ＺｒＯ２ボール７５０ｇとメチルアルコール１１７ｍｇを充填し、ボールミルを１００ｒｐｍで回転させながら３０時間湿式粉砕を行った。得られた第１のスラリーを、減圧下、５０℃で乾燥し混合粉体を調製した。混合粉体１００重量部（２０ｇ）に対して５０重量部（１０ｇ）の蒸留水を加え混練した後、含水物を室温下で静置し硬化させた。硬化した含水物全量を３２メッシュふるいに通して、１５００℃で２時間焼成し、粉末状のＢａＡｌ１２Ｏ１９を得た。得られたＢａＡｌ１２Ｏ１９の細孔容積及び比表面積を図３に示し、細孔径分布を図２（ｂ）に示す。図２（ｂ）の横軸はＢａＡｌ１２Ｏ１９の細孔径ｄｐ［ｎｍ］、縦軸はログ微分細孔容積ｄｐ／ｄ（ｌｏｇｄｐ）［ｃｍ３／ｇ］を示している。また、同粉末中にＢａＡｌ１２Ｏ１９が含まれていることはＸ線回折にて確認した。
図２（ｂ）によれば、上述の方法により製造したＢａＡｌ１２Ｏ１９は、およそ１２０ｎｍ〜１３０ｎｍ付近に単一のピークを有する細孔径分布を備えたＢａＡｌ１２Ｏ１９となっていることが確認できる。
[5] Method for preparing a carrier having a pore size distribution of bimodal structure
(1) Preparation of BaAl 12 O 19 having a pore size distribution peak in the pore size range of 30 nm to 200 nm
A magnetic ball mill with an outer diameter of 120φ and an inner volume of 900 cm3, BaAl 2 O 4 (High Purity Chemical Laboratory Co., Ltd., purity 99.9%) 16.7 g, α-alumina (Nihon Light Metal Co., Ltd.) 33.3 g, ZrO Two balls (750 g) and methyl alcohol (117 mg) were filled, and wet milling was performed for 30 hours while rotating the ball mill at 100 rpm. The obtained first slurry was dried at 50 ° C. under reduced pressure to prepare a mixed powder. After 50 parts by weight (10 g) of distilled water was added to 100 parts by weight (20 g) of the mixed powder and kneaded, the hydrated product was allowed to stand at room temperature and cured. The entire amount of the cured hydrated product was passed through a 32 mesh sieve and baked at 1500 ° C. for 2 hours to obtain powdered BaAl 12 O 19 . The pore volume and specific surface area of the obtained BaAl 12 O 19 are shown in FIG. 3, and the pore diameter distribution is shown in FIG. 2 (b). In FIG. 2B, the horizontal axis indicates the pore diameter d p [nm] of BaAl 12 O 19 and the vertical axis indicates the log differential pore volume d p / d (logd p ) [cm 3 / g]. Further, it was confirmed by X-ray diffraction that BaAl 12 O 19 was contained in the powder.
According to FIG. 2 (b), BaAl 12 O 19 prepared by the method described above, confirmed that a BaAl 12 O 19 having a pore size distribution with a single peak near about 120nm~130nm it can.
（２）バイモーダルＢａＡｌ１２Ｏ１９の調製
（１）で得たＢａＡｌ１２Ｏ１９を３６．４ｇとグリコール酸（デュポン株式会社製、７０％水溶液）９．７ｇとを混合し、さらに、ＺｒＯ２ボール７５０ｇ及び蒸留水を充填し、ボールミル１００ｒｐｍで回転させながら５時間湿式粉砕を行い第２のスラリーを得た。
一方、外径１２０φ、内容積９００ｃｍ３の磁製ボールミルにＢａＡｌ２Ｏ４（株式会社高純度化学研究所、純度９９．９％）１５．６ｇ、水酸化アルミナ（日本軽金属株式会社製）４７．７g、グリコール酸（デュポン株式会社製、７０％水溶液）３９．９ｇを混合し、ｐＨを３．０に調整して更に、ＺｒＯ２ボールを７５０ｇと蒸留水を充填して、ボールミルを１００ｒｐｍで回転させながら６０時間湿式粉砕を行って第３のスラリーを得た。
(2) Preparation of bimodal BaAl 12 O 19 36.4 g of BaAl 12 O 19 obtained in (1) and 9.7 g of glycolic acid (manufactured by DuPont, 70% aqueous solution) are mixed, and further ZrO 2 Filled with 750 g of balls and distilled water and wet-ground for 5 hours while rotating at a ball mill of 100 rpm, a second slurry was obtained.
On the other hand, in a magnetic ball mill having an outer diameter of 120φ and an inner volume of 900 cm 3 , 15.6 g of BaAl 2 O 4 (high purity chemical research institute, purity 99.9%), alumina hydroxide (manufactured by Nippon Light Metal Co., Ltd.) 47. 7 g and glycolic acid (manufactured by DuPont, 70% aqueous solution) 39.9 g are mixed, pH is adjusted to 3.0, ZrO 2 balls are filled with 750 g and distilled water, and the ball mill is rotated at 100 rpm. Then, wet grinding was performed for 60 hours to obtain a third slurry.
次いで、第２、第３のスラリーを混合し、１５０℃の大気雰囲気下で静置乾燥させ混合粉末を得た。この混合粉末を８００℃の大気雰囲気中で２時間焼成することにより粉末状のＢａＡｌ１２Ｏ１９を得た。得られたＢａＡｌ１２Ｏ１９の細孔容積及び比表面積を図３に示し、細孔径分布を図２（ａ）に示す。また、同粉末中にＢａＡｌ１２Ｏ１９が含まれていることはＸ線回折にて確認した。
図２（ａ）によれば、上述の方法により製造したＢａＡｌ１２Ｏ１９は、およそ４ｎｍ付近に第１のピークを有し、およそ１４０ｎｍ付近に第２のピークを有する細孔径分布を備えたバイモーダル構造のＢａＡｌ１２Ｏ１９となっていることが確認できる。そして本例では例えば第１のピークの前後において、ログ微分細孔容積の値が当該第１のピークの半値となる細孔径の範囲を第１の細孔径領域とした。また第２のピークより小径の位置にてログ微分細孔容積が当該第２のピークの半値となる細孔径を第２の細孔径領域の下端とし、細孔径分布の測定上限である細孔径２００ｎｍの位置を第２の細孔径領域の上端とした。
Next, the second and third slurries were mixed and left to dry in an air atmosphere at 150 ° C. to obtain a mixed powder. This mixed powder was fired in an air atmosphere at 800 ° C. for 2 hours to obtain powdered BaAl 12 O 19 . The pore volume and specific surface area of the obtained BaAl 12 O 19 are shown in FIG. 3, and the pore size distribution is shown in FIG. Further, it was confirmed by X-ray diffraction that BaAl 12 O 19 was contained in the powder.
According to FIG. 2 (a), the BaAl 12 O 19 produced by the above-described method has a first peak around 4 nm and a pore size distribution having a second peak around 140 nm. It can be confirmed that it is BaAl 12 O 19 having a modal structure. In this example, for example, before and after the first peak, the pore diameter range in which the value of the log differential pore volume is half the value of the first peak is defined as the first pore diameter region. In addition, the pore diameter at which the log differential pore volume is half the value of the second peak at a position smaller than the second peak is defined as the lower end of the second pore diameter region, and the pore diameter is 200 nm, which is the upper limit of measurement of the pore diameter distribution. Was the upper end of the second pore diameter region.
［実施例１］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９：７５．８ｇと、ＺｒＯ２（第一稀元素株式会社）：２４．２ｇとを乳鉢混合することで粉末状の担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：０．３２）。この混合粉末担体５０gにジニトロジアンミン白金溶液（田中貴金属工業株式会社、Ｐｔ金属として８．４質量％含有）１．７ｇを加えて、その全量を含浸させた後、ホットプレートを用いて蒸発乾固させて、さらに１１０℃の大気雰囲気中で３時間乾燥後、４００℃の大気雰囲気中で３時間焼成し、排ガス浄化触媒を得た。
［実施例１］に係る排ガス浄化触媒の物性値（活性金属割合、比表面積）と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。また当該排ガス浄化触媒に用いたＢａＡｌ１２Ｏ１９のＸ線回折パターンを図４（ａ）に示す。同パターンによれば、ＢａＡｌ１２Ｏ１９特有の面指数（１０７）のピークを確認できる。
[Example 1]
A powdery carrier was prepared by mixing mortar with BaAl 12 O 19 : 75.8 g having a pore size distribution of bimodal structure and ZrO 2 (Daiichi Rare Element Co., Ltd.): 24.2 g (BaAl 12 O 19 : ZrO 2 = 1: 0.32). After adding 1.7 g of dinitrodiammine platinum solution (Tanaka Kikinzoku Kogyo Co., Ltd., containing 8.4% by mass as Pt metal) to 50 g of this mixed powder carrier, impregnating the entire amount, evaporating to dryness using a hot plate The catalyst was further dried in an air atmosphere at 110 ° C. for 3 hours and then calcined in an air atmosphere at 400 ° C. for 3 hours to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical properties (active metal ratio, specific surface area) of the exhaust gas purifying catalyst according to [Example 1] and the measurement results of the light-off temperature before and after the high temperature durability treatment. FIG. 4A shows an X-ray diffraction pattern of BaAl 12 O 19 used for the exhaust gas purification catalyst. According to this pattern, the peak of the surface index (107) peculiar to BaAl 12 O 19 can be confirmed.
［参考例２］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９：９５．２ｇとＺｒＯ２：４．８ｇとを混合することで粉末状担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：０．０５）。この混合粉末担体に［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［参考例２］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Reference Example 2]
A powdery carrier was prepared by mixing BaAl 12 O 19 : 95.2 g and ZrO 2 : 4.8 g having a pore size distribution of bimodal structure (BaAl 12 O 19 : ZrO 2 = 1: 0.05). . Pt was supported on this mixed powder carrier in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Reference Example 2] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［実施例３］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９：８５．６ｇとＺｒＯ２：１４．４ｇとを混合することで粉末状担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：０．１７）。この混合粉末担体に［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［実施例３］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Example 3]
BaAl 12 O 19 : 85.6 g having a pore size distribution of bimodal structure and ZrO 2 : 14.4 g were mixed to prepare a powdery carrier (BaAl 12 O 19 : ZrO 2 = 1: 0.17). . Pt was supported on this mixed powder carrier in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Example 3] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［実施例４］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９：６１．１ｇとＺｒＯ２：３８．９ｇとを混合することで粉末状担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：０．６４）。この混合粉末担体に［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［実施例４］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Example 4]
BaAl 12 O 19 : 61.1 g having a pore size distribution of bimodal structure and ZrO 2 : 38.9 g were mixed to prepare a powdery carrier (BaAl 12 O 19 : ZrO 2 = 1: 0.64). . Pt was supported on this mixed powder carrier in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Example 4] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［実施例５］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９：３６．０ｇとＺｒＯ２：６４．０ｇとを混合することで粉末状担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：１．７８）。この混合粉末担体に［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［実施例５］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Example 5]
BaAl 12 O 19 : 36.0 g having a pore size distribution of bimodal structure and ZrO 2 : 64.0 g were mixed to prepare a powdery support (BaAl 12 O 19 : ZrO 2 = 1: 1.78). . Pt was supported on this mixed powder carrier in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Example 5] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［実施例６］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９：２０．７ｇとＺｒＯ２：７９．３ｇとを混合することで粉末状担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：３．８３）。この混合粉末担体に［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［実施例６］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Example 6]
BaAl 12 O 19 : 20.7 g having a pore size distribution of bimodal structure and ZrO 2 : 79.3 g were mixed to prepare a powdery support (BaAl 12 O 19 : ZrO 2 = 1: 3.83). . Pt was supported on this mixed powder carrier in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical properties of the exhaust gas purifying catalyst according to [Example 6] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［実施例７］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９：１５．６ｇとＺｒＯ２：８４．４ｇとを混合することで粉末状担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：５．４１）。この混合粉末担体に［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［実施例７］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Example 7]
BaAl 12 O 19 : 15.6 g having a pore size distribution of bimodal structure and ZrO 2 : 84.4 g were mixed to prepare a powdery support (BaAl 12 O 19 : ZrO 2 = 1: 5.41). . Pt was supported on this mixed powder carrier in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Example 7] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［実施例８］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９：１０．４ｇとＺｒＯ２：８９．６ｇとを混合することで粉末状担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：８．６２）。この混合粉末担体に［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［実施例５］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Example 8]
A powdery carrier was prepared by mixing BaAl 12 O 19 : 10.4 g having a pore size distribution of bimodal structure and 89.6 g of ZrO 2 (BaAl 12 O 19 : ZrO 2 = 1: 8.62). . Pt was supported on this mixed powder carrier in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Example 5] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［比較例１］
細孔径分布がバイモーダル構造ではない［５］−（１）に記載の第１のＢａＡｌ１２Ｏ１９に：７５．８ｇとＺｒＯ２：２４．２ｇとを混合することで粉末状担体を調製した（ＢａＡｌ１２Ｏ１９：ＺｒＯ２＝１：８．６２）。この混合粉末担体に［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［比較例１］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。また当該排ガス浄化触媒に用いたＢａＡｌ１２Ｏ１９のＸ線回折パターンを図４（ｂ）に示す。同パターンによれば、ＢａＡｌ１２Ｏ１９に特有の面指数（１０７）のピークを確認できる。
[Comparative Example 1]
A powdery carrier was prepared by mixing 75.8 g and ZrO 2 : 24.2 g in the first BaAl 12 O 19 described in [5]-(1) whose pore size distribution is not a bimodal structure. (BaAl 12 O 19 : ZrO 2 = 1: 8.62). Pt was supported on this mixed powder carrier in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical properties of the exhaust gas purifying catalyst according to [Comparative Example 1] and the measurement results of the light-off temperature before and after the high temperature durability treatment. FIG. 4B shows an X-ray diffraction pattern of BaAl 12 O 19 used for the exhaust gas purification catalyst. According to this pattern, the peak of the surface index (107) peculiar to BaAl 12 O 19 can be confirmed.
［比較例２］
細孔径分布がバイモーダル構造ではない［５］−（１）に記載の第１のＢａＡｌ１２Ｏ１９をＺｒＯ２とは混合せず、単体のＢａＡｌ１２Ｏ１９：５０ｇに［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［比較例２］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Comparative Example 2]
The first BaAl 12 O 19 described in [5]-(1) whose pore size distribution is not a bimodal structure is not mixed with ZrO 2, and BaAl 12 O 19 : 50 g as a simple substance [Example 1] In the same manner, Pt was supported and an exhaust gas purification catalyst was obtained.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Comparative Example 2] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［比較例３］
細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９をＺｒＯ２とは混合せず、単体のＢａＡｌ１２Ｏ１９：５０ｇに［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［比較例２］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Comparative Example 3]
BaAl 12 O 19 having a pore size distribution of bimodal structure is not mixed with ZrO 2, and Pt is supported on a single piece of BaAl 12 O 19 : 50 g in the same manner as in [Example 1], and an exhaust gas purification catalyst is used. Obtained.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Comparative Example 2] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［比較例４］
ＢａＡｌ１２Ｏ１９とは混合していない単体のＺｒＯ２：５０ｇに［実施例１］と同様の要領にてＰｔを担持し、排ガス浄化触媒を得た。
［比較例２］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Comparative Example 4]
Pt was supported on 50 g of simple ZrO 2 that was not mixed with BaAl 12 O 19 in the same manner as in [Example 1] to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical property values of the exhaust gas purifying catalyst according to [Comparative Example 2] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
［比較例５］
酸化アルミニウム粉末（和光純薬工業株式会社製、和光特級）からなる担体５０ｇにジニトロジアンミン白金溶液（Ｐｔとして４．５質量％含有）３．３３ｇを加えて、その全量を含浸させ、ホットプレートを用いて、蒸発乾固させて、さらに１１０℃の大気雰囲気中で３時間乾燥後、４００℃の大気雰囲気中で３時間焼成し、排ガス浄化触媒を得た。
［比較例５］に係る排ガス浄化触媒の物性値と高温耐久処理前後でのライトオフ温度の測定結果を図５に示す。
[Comparative Example 5]
To 50 g of a carrier made of aluminum oxide powder (Wako Pure Chemical Industries, Ltd., Wako Special Grade), add 3.33 g of dinitrodiammine platinum solution (containing 4.5 mass% as Pt), impregnate the whole amount, Then, it was evaporated to dryness, further dried in an air atmosphere at 110 ° C. for 3 hours, and then calcined in an air atmosphere at 400 ° C. for 3 hours to obtain an exhaust gas purification catalyst.
FIG. 5 shows the physical properties of the exhaust gas purifying catalyst according to [Comparative Example 5] and the measurement results of the light-off temperature before and after the high temperature durability treatment.
図５に示した結果によれば、細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９と、ＺｒＯ２とを含む担体に、活性金属としてＰｔを担持した（実施例１〜８）の排ガス浄化触媒においては、高温耐久処理後のＴ５０温度が４１０〜４７７℃の範囲であり、各比較例と比べて全般的に高温耐久処理後のＴ５０温度が低い。また高温耐久処理前後のＴ５０温度差は、２１〜５１℃の範囲であり、この値についても各比較例と比べてＴ５０温度差は小さく良好な耐久性が確認された。但し、高温耐久化処理前の温度が温度計のレンジを超えた参考例２ではＴ５０温度差を算出しなかった。 According to the results shown in FIG. 5, the exhaust gas purifying catalyst in which Pt was supported as an active metal on a carrier containing BaAl 12 O 19 having a pore size distribution of bimodal structure and ZrO 2 (Examples 1 to 8). , The T50 temperature after the high temperature endurance treatment is in the range of 410 to 477 ° C., and the T50 temperature after the high temperature endurance treatment is generally lower than in each comparative example. Further, the T50 temperature difference before and after the high temperature durability treatment was in the range of 21 to 51 ° C., and also for this value, the T50 temperature difference was small compared to each comparative example, and good durability was confirmed. However, T50 temperature difference was not calculated in Reference Example 2 in which the temperature before the high temperature durability treatment exceeded the range of the thermometer.
一方で、細孔径分布がバイモーダル構造ではないＢａＡｌ１２Ｏ１９をＺｒＯ２と混合した担体（比較例１）、細孔径分布がバイモーダル構造ではないＢａＡｌ１２Ｏ１９のみからなる担体（比較例２）、細孔径分布がバイモーダル構造のＢａＡｌ１２Ｏ１９のみからなる担体（比較例３）、ＺｒＯ２のみからなる担体（比較例４）、酸化アルミニウムのみからなる担体（比較例５）に、活性金属としてＰｔを担持した排ガス浄化触媒（比較例１〜５）では、高温耐久処理後のＴ５０温度が４８６〜６２１℃であり各実施例と比べて高温である。また、Ｔ５０温度差についても９１〜２３４℃であり、各実施例よりも耐久性が低い。
これらの実験結果から（実施例１〜８）に係る排ガス浄化触媒は、良好な高温耐久性を備えているといえる。
On the other hand, a carrier (Comparative Example 1) in which BaAl 12 O 19 whose pore size distribution is not a bimodal structure is mixed with ZrO 2, and a carrier consisting only of BaAl 12 O 19 whose pore size distribution is not a bimodal structure (Comparative Example 2). ), A carrier composed only of BaAl 12 O 19 having a pore size distribution of bimodal structure (Comparative Example 3), a carrier composed only of ZrO 2 (Comparative Example 4), and a carrier composed solely of aluminum oxide (Comparative Example 5). In the exhaust gas purification catalyst (Comparative Examples 1 to 5) carrying Pt as a metal, the T50 temperature after the high-temperature endurance treatment is 486 to 621 ° C., which is higher than in each example. Moreover, it is 91-234 degreeC also about T50 temperature difference, and its durability is lower than each Example.
From these experimental results, it can be said that the exhaust gas purifying catalysts according to (Examples 1 to 8) have good high-temperature durability.
ここで（実施例１〜８）に用いたＢａＡｌ１２Ｏ１９の細孔径分布は、図２（ａ）に示すように第１、第２のピークに近い細孔径を持つ細孔がこれらのピークの前後に分布している。そして（実施例１〜８）の排ガス浄化触媒の作用は、前記第１、第２のピークの細孔径の細孔のみならず、これら第１、第２のピーク付近に分布している細孔径の細孔の作用も相俟って良好な高温耐久性が発揮されたものといえる。 Here, the pore diameter distribution of BaAl 12 O 19 used in (Examples 1 to 8) is such that pores having pore diameters close to the first and second peaks are those peaks as shown in FIG. It is distributed before and after. The action of the exhaust gas purifying catalyst of (Examples 1 to 8) is not only the pores having the pore diameters of the first and second peaks, but also the pore diameters distributed in the vicinity of the first and second peaks. It can be said that good high-temperature durability was exhibited in combination with the action of the pores.
従ってバイモーダル構造のＢａＡｌ１２Ｏ１９におけるピークの位置は、図２（ａ）に示した例に限定されるものではなく、少なくとも例えば図２（ａ）に示した第１の細孔径領域（３．４ｎｍ以上、５．３ｎｍ以下の領域）に第１のピークが存在し、第２の細孔径領域（５４ｎｍ以上、２００ｎｍ以下の領域）に第２のピークが存在する場合には、（比較例１〜５）の場と比べて高い高温耐久性が発揮されると考えられる。 Therefore, the position of the peak in the BaAl 12 O 19 having the bimodal structure is not limited to the example shown in FIG. 2A, and at least, for example, the first pore diameter region (3) shown in FIG. In the case where the first peak exists in the region of 0.4 nm or more and 5.3 nm or less) and the second peak exists in the second pore size region (region of 54 nm or more and 200 nm or less) (Comparative Example) It is considered that the high temperature durability is higher than in the cases of 1-5).
Claims (12)
ＺｒＯ２と、を含む担体であって、
ＢａＡｌ１２Ｏ１９に対するＺｒＯ２の質量比が１：０．１〜１：２０の範囲にある担体に活性金属が担持されていることを特徴とする排ガス浄化触媒。 BaAl 12 O 19 having a bimodal structure having a peak of a pore size distribution in a first pore size region and a second pore size region having a larger pore size than the first pore size region,
ZrO 2 and a carrier comprising:
An exhaust gas purifying catalyst, wherein an active metal is supported on a carrier having a mass ratio of ZrO 2 to BaAl 12 O 19 in a range of 1: 0.1 to 1:20.
（１）アルミニウム含有化合物、第２の細孔径領域に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９、ＢａＡｌ２Ｏ４及び有機酸を含む混合物であって、この混合物中のアルミニウムとバリウムのモル比が１：０．０２〜１：０．１の範囲であり、アルミニウムと有機酸のモル比が１：０．１〜１：０．５の範囲であるものを７００℃以上、１３００℃以下の温度で焼成し、第１の細孔径領域と、この第１の細孔径領域よりも細孔径の大きな前記第２の細孔径領域とに細孔径分布のピークを有するバイモーダル構造のＢａＡｌ１２Ｏ１９を調製する工程。
（２）このバイモーダル構造のＢａＡｌ１２Ｏ１９とＺｒＯ２とを混合して担体を調製する工程。
（３）前記担体にＰｔ、Ｐｄ、Ｒｈ、Ｒｕ、Ｏｓ、Ｉｒ、Ａｕ及びＡｇからなる貴金属群から選ばれる少なくとも１種類以上の活性金属を担持させる工程。 The manufacturing method of the exhaust gas purification catalyst characterized by including the process of following (1)-(3).
(1) A mixture containing an aluminum-containing compound, BaAl 12 O 19 , BaAl 2 O 4 having a pore size distribution peak in the second pore size region, and an organic acid, the molar ratio of aluminum to barium in the mixture Is in the range of 1: 0.02 to 1: 0.1, and the molar ratio of aluminum to organic acid is in the range of 1: 0.1 to 1: 0.5. BaAl 12 O 19 having a bimodal structure having a pore size distribution peak in the first pore size region and the second pore size region having a pore size larger than the first pore size region. Preparing the step.
(2) A step of preparing a carrier by mixing BaAl 12 O 19 having this bimodal structure and ZrO 2 .
(3) A step of supporting at least one active metal selected from a noble metal group consisting of Pt, Pd, Rh, Ru, Os, Ir, Au, and Ag on the carrier.
［１］第１の細孔径領域と、この第１の細孔径領域よりも細孔径の大きな第２の細孔径領域とに細孔径分布のピークを有するバイモーダル構造のＢａＡｌ１２Ｏ１９と、ＺｒＯ２とを含む担体を調製する工程。
［２］前工程で得られた担体に活性金属溶液を含浸させ、３５０〜５５０℃で焼成させて、前記担体に活性金属を担持する工程。 The manufacturing method of the exhaust gas purification catalyst characterized by including the process of following [1] and [2].
[1] BaAl 12 O 19 having a bimodal structure having a peak of a pore size distribution in a first pore size region and a second pore size region having a pore size larger than the first pore size region, and ZrO And 2. preparing a carrier comprising
[2] A step of impregnating the support obtained in the previous step with an active metal solution and firing at 350 to 550 ° C. to support the active metal on the support.
［１］ＢａＡｌ２Ｏ４、アルミニウム含有化合物及び有機溶媒からなる分散液を湿式処理することにより第１のスラリーを調製し、該第１のスラリーを１２００〜１６００℃にて焼成することにより、第２の細孔径領域に細孔径分布のピークを有するＢａＡｌ１２Ｏ１９を調製する工程。
［２］前工程［１］で得られたＢａＡｌ１２Ｏ１９と有機酸水溶液の混合物を湿式粉砕処理し、第２のスラリーを調製する工程。
［３］ＢａＡｌ２Ｏ４とアルミニウム含有化合物に有機酸水溶液を加え、ｐＨ３．０〜４．０の混合液を調整し、該混合液を湿式粉砕処理して第３のスラリーを調製する工程。
［４］前記第２のスラリーと第３のスラリーを混合し、７００〜１３００℃で焼成して、前記バイモーダル構造のＢａＡｌ１２Ｏ１９を調製する工程。 The method for producing an exhaust gas purification catalyst according to claim 7, wherein the bimodal BaAl 12 O 19 is obtained by a production method including the following steps [1] to [4].
[1] A first slurry is prepared by wet-treating a dispersion composed of BaAl 2 O 4 , an aluminum-containing compound and an organic solvent, and the first slurry is fired at 1200 to 1600 ° C. A step of preparing BaAl 12 O 19 having a pore size distribution peak in the pore size region of No. 2;
[2] A step of preparing a second slurry by wet-grinding the mixture of BaAl 12 O 19 and the organic acid aqueous solution obtained in the previous step [1].
[3] A step of preparing a third slurry by adding an organic acid aqueous solution to BaAl 2 O 4 and an aluminum-containing compound, adjusting a mixed solution having a pH of 3.0 to 4.0, and wet-pulverizing the mixed solution.
[4] A step of preparing BaAl 12 O 19 having the bimodal structure by mixing the second slurry and the third slurry and baking the mixture at 700 to 1300 ° C.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015037536A1 (en) * | 2013-09-10 | 2015-03-19 | 新日鐵住金株式会社 | Oxidation catalyst, exhaust gas treatment device, regenerative combustion burner, method for oxidizing combustible components contained in gas, and method for removing nitrogen oxide contained in gas |
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| WO2015037536A1 (en) * | 2013-09-10 | 2015-03-19 | 新日鐵住金株式会社 | Oxidation catalyst, exhaust gas treatment device, regenerative combustion burner, method for oxidizing combustible components contained in gas, and method for removing nitrogen oxide contained in gas |
| JPWO2015037536A1 (en) * | 2013-09-10 | 2017-03-02 | 新日鐵住金株式会社 | Oxidation catalyst, exhaust gas treatment device, regenerative combustion burner, method for oxidizing combustible components in gas, and method for removing nitrogen oxides in gas |
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