JP6612546B2 - Exhaust gas purification catalyst and exhaust gas purification filter - Google Patents
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- 239000003054 catalyst Substances 0.000 title claims description 109
- 238000000746 purification Methods 0.000 title claims description 34
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 13
- 239000002184 metal Substances 0.000 claims description 13
- 229910052792 caesium Inorganic materials 0.000 claims description 7
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 claims description 7
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 7
- 239000002131 composite material Substances 0.000 claims description 6
- 229910044991 metal oxide Inorganic materials 0.000 claims description 6
- 150000004706 metal oxides Chemical class 0.000 claims description 6
- 239000000919 ceramic Substances 0.000 claims description 5
- 229910052720 vanadium Inorganic materials 0.000 claims description 5
- 229910052936 alkali metal sulfate Inorganic materials 0.000 claims description 2
- 229910003455 mixed metal oxide Inorganic materials 0.000 claims 1
- 239000007789 gas Substances 0.000 description 42
- 239000013618 particulate matter Substances 0.000 description 27
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 17
- 238000002485 combustion reaction Methods 0.000 description 16
- 238000011156 evaluation Methods 0.000 description 16
- 150000003839 salts Chemical class 0.000 description 15
- 238000012360 testing method Methods 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 14
- 230000000694 effects Effects 0.000 description 13
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical group [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 9
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 9
- FLJPGEWQYJVDPF-UHFFFAOYSA-L caesium sulfate Chemical compound [Cs+].[Cs+].[O-]S([O-])(=O)=O FLJPGEWQYJVDPF-UHFFFAOYSA-L 0.000 description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- 230000008018 melting Effects 0.000 description 6
- 238000002844 melting Methods 0.000 description 6
- 230000005068 transpiration Effects 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 5
- 150000001340 alkali metals Chemical class 0.000 description 4
- 230000003993 interaction Effects 0.000 description 4
- 239000000395 magnesium oxide Substances 0.000 description 4
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 3
- 229910001960 metal nitrate Inorganic materials 0.000 description 3
- -1 platinum group metals Chemical class 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
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- 239000001301 oxygen Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000000851 scanning transmission electron micrograph Methods 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910013553 LiNO Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910001963 alkali metal nitrate Inorganic materials 0.000 description 1
- 229910001964 alkaline earth metal nitrate Inorganic materials 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
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- 230000015556 catabolic process Effects 0.000 description 1
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- 238000006243 chemical reaction Methods 0.000 description 1
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- 229910052878 cordierite Inorganic materials 0.000 description 1
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- 238000006731 degradation reaction Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000000374 eutectic mixture Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
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- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
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- Processes For Solid Components From Exhaust (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
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Description
本発明は、ディーゼルエンジン等の排ガスに含まれる粒子状物質を燃焼して、排ガスを浄化する排ガス浄化触媒及び排ガス浄化フィルタに関するものである。 The present invention relates to an exhaust gas purification catalyst and an exhaust gas purification filter that purify exhaust gas by burning particulate matter contained in exhaust gas such as a diesel engine.
ディーゼルエンジンは炭素等からなる粒子状物質（ＰＭ：Ｐａｒｔｉｃｕｌａｔｅ Ｍａｔｔｅｒ）を排出することが課題であり、ディーゼルパティキュレートフィルタ（ＤＰＦ：Ｄｉｅｓｅｌ Ｐａｒｔｉｃｕｌａｔｅ Ｆｉｌｔｅｒ）を排ガス経路に設置して、ＰＭを捕集している。捕集されたＰＭは、定期的に排ガス温度を上昇させて燃焼除去する。ＰＭを熱だけで燃焼するためには６００℃以上の高温が必要になるので、より低温でＰＭを燃焼するために触媒作用を利用して燃焼を促進する。 Diesel engines have a problem of discharging particulate matter (PM) consisting of carbon and the like, and a diesel particulate filter (DPF: Diesel Particulate Filter) is installed in the exhaust gas path to collect PM. Yes. The collected PM is burned and removed by periodically raising the exhaust gas temperature. In order to burn PM only with heat, a high temperature of 600 ° C. or higher is required. Therefore, in order to burn PM at a lower temperature, combustion is promoted using a catalytic action.
現在、排ガス浄化触媒には白金、パラジウム等の白金族金属が広く使用されている。これは白金族金属の排ガス浄化触媒が、良好なＰＭ燃焼性能と耐久性を持つためである。しかし、白金族金属は希少で、また高価であり、自動車排ガス浄化触媒においては省白金族使用、白金族代替に関する研究が世界中で行われている（非特許文献１参照）。 Currently, platinum group metals such as platinum and palladium are widely used for exhaust gas purification catalysts. This is because the platinum group metal exhaust gas purification catalyst has good PM combustion performance and durability. However, platinum group metals are rare and expensive, and research on platinum group use and platinum group substitution in automobile exhaust gas purification catalysts has been conducted all over the world (see Non-Patent Document 1).
白金族金属不使用の排ガス浄化触媒の一つに、アルカリ金属等からなる溶融塩型触媒（または溶融易動型触媒とも言う）がある。溶融塩型触媒はＰＭとの反応温度近傍で溶融し液相となるので、触媒とＰＭとの接触は飛躍的に増大し、性能が良化すると考えられている。溶融塩型触媒には、例えば、セシウム（Ｃｓ）とバナジウム（Ｖ）の複合金属酸化物（以下、ＣｓＶ酸化物と記載）があり、いくつかあるＣｓＶ酸化物の中でも特にＣｓ3ＶＯ4がＰＭに対して高活性であることが報告されている（非特許文献２参照）。 One of the exhaust gas purification catalysts that do not use platinum group metals is a molten salt type catalyst (or also referred to as a melt-movable catalyst) made of an alkali metal or the like. Since the molten salt type catalyst melts in the vicinity of the reaction temperature with PM and becomes a liquid phase, the contact between the catalyst and PM is considered to increase dramatically and the performance is improved. The molten salt type catalyst includes, for example, a composite metal oxide of cesium (Cs) and vanadium (V) (hereinafter referred to as CsV oxide). Among several CsV oxides, Cs 3 VO 4 is particularly PM. Has been reported to be highly active (see Non-Patent Document 2).
また、塩基性担体に担持された金属硝酸塩からなる溶融塩型触媒もある（特許文献１参照）。 There is also a molten salt type catalyst composed of a metal nitrate supported on a basic support (see Patent Document 1).
前記塩基性担体としてはマグネシアスピネル等が好ましく、前記金属硝酸塩としてはアルカリ金属又はアルカリ土類金属の硝酸塩が好ましく、ＬｉＮＯ3が最も好ましいと報告されている。 The basic carrier is preferably magnesia spinel, the metal nitrate is preferably an alkali metal or alkaline earth metal nitrate, and LiNO 3 is reported to be most preferable.
ＣｓＶ酸化物等の溶融塩型触媒は液相となることで十分な性能を発揮し、融点が低いもの程、ＰＭの燃焼温度も低くなる傾向がある。一方、液相であるために排ガスと接触して移動する懸念や、蒸散する懸念がある。そして融点が低いもの程、これらの懸念は高まる。また、溶融塩型触媒によく使用されるアルカリ金属は、金属の中では蒸気圧が大きく、蒸散の懸念がある。 Molten salt type catalysts such as CsV oxides exhibit sufficient performance when in a liquid phase, and the lower the melting point, the lower the combustion temperature of PM. On the other hand, since it is in a liquid phase, there are concerns that it will move in contact with exhaust gas and that it may evaporate. And the lower the melting point, the higher these concerns. Moreover, the alkali metal often used for the molten salt type catalyst has a high vapor pressure among the metals, and there is a concern of transpiration.
従って、このような従来の溶融塩型触媒は、白金族金属触媒に比べて耐久性に劣るという課題を有していた。 Therefore, such a conventional molten salt type catalyst has a problem that it is inferior in durability compared with a platinum group metal catalyst.
そこで本発明は、上記従来の課題を解決するものであり、耐久性を向上させた溶融塩型排ガス浄化触媒及びこの触媒をコーティングした排ガス浄化フィルタを提供することを目的とする。 The present invention solves the above-described conventional problems, and an object thereof is to provide a molten salt type exhaust gas purification catalyst with improved durability and an exhaust gas purification filter coated with this catalyst.
そして、この目的を達成するために、本発明の排ガス浄化触媒は、セシウムとバナジウムの複合金属酸化物と、アルミナを含むことを特徴としたものであり、これにより所期の目的を達成するものである。 In order to achieve this object, the exhaust gas purification catalyst of the present invention is characterized in that it contains a composite metal oxide of cesium and vanadium and alumina, thereby achieving the intended object. It is.
また本発明の排ガス浄化フィルタは、本発明の排ガス浄化触媒を、セラミックス又は金属のフィルタに塗布したことを特徴としたものであり、これにより所期の目的を達成するものである。 The exhaust gas purification filter of the present invention is characterized in that the exhaust gas purification catalyst of the present invention is applied to a ceramic or metal filter, thereby achieving the intended purpose.
本発明の排ガス浄化触媒は、セシウムとバナジウムの複合金属酸化物と、アルミナを含むことを特徴とした。 The exhaust gas purifying catalyst of the present invention is characterized by containing a composite metal oxide of cesium and vanadium and alumina.
セシウム（Ｃｓ）とバナジウム（Ｖ）の複合金属酸化物（ＣｓＶ酸化物）をアルミナ系担体に担持させることにより、触媒と担体の相互作用が増大し、耐久性を向上させることができる。 By supporting a composite metal oxide (CsV oxide) of cesium (Cs) and vanadium (V) on an alumina-based support, the interaction between the catalyst and the support is increased, and durability can be improved.
これにより、高活性と高耐久性を両立した溶融塩型排ガス浄化触媒を提供することができる。 Thereby, the molten salt type exhaust gas purifying catalyst having both high activity and high durability can be provided.
また本発明の排ガス浄化フィルタは、本発明の排ガス浄化触媒を、セラミックス又は金属のフィルタに塗布したことを特徴とした。 The exhaust gas purification filter of the present invention is characterized in that the exhaust gas purification catalyst of the present invention is applied to a ceramic or metal filter.
これにより、高活性と高耐久性を両立した溶融塩型排ガス浄化触媒をコーティングした排ガス浄化フィルタを提供することができる。 Thereby, the exhaust gas purification filter coated with the molten salt type exhaust gas purification catalyst that achieves both high activity and high durability can be provided.
本発明者らは、上記で述べた、ＣｓＶ酸化物触媒の活性と耐久性の両立という、相矛盾する極めて難しい課題を解決するため、触媒と担体の相互作用に着目し、アルミナ系担体と強く結合したＣｓＶ酸化物触媒が、高活性と高耐久性を両立することを見出した。 In order to solve the contradicting extremely difficult problem of compatibility between the activity and durability of the CsV oxide catalyst described above, the present inventors have paid attention to the interaction between the catalyst and the carrier, It has been found that the combined CsV oxide catalyst achieves both high activity and high durability.
すなわち、本発明の請求項１に記載の排ガス浄化触媒は、ＣｓＶ酸化物と、アルミナを含むことを特徴としたものであり、触媒と担体の相互作用が増大し、耐久性が向上した。
That is, the exhaust gas purifying catalyst according to
ＣｓＶ酸化物はＰＭに酸素を供給し、これを燃焼するという機能を有し、ＣｓＶ酸化物としては、Ｃｓ2Ｖ4Ｏ11、ＣｓＶＯ3、Ｃｓ3ＶＯ4等を用いることができるが、Ｃｓ2Ｖ4Ｏ11が好ましい。 The CsV oxide has a function of supplying oxygen to PM and burning it. As the CsV oxide, Cs 2 V 4 O 11 , CsVO 3 , Cs 3 VO 4, etc. can be used. 2 V 4 O 11 is preferred.
アルミナは、触媒担体として様々なものが提案されているが、高比表面積を持ち、耐熱性に優れたγ−アルミナ（Ａｌ2Ｏ3）が好ましい。また、耐熱性を向上するためにセリウム（Ｃｅ）やランタン（Ｌａ）と言った希土類、バリウム（Ｂａ）等を添加したものを用いても良い。 Various aluminas have been proposed as catalyst carriers, but γ-alumina (Al 2 O 3 ) having a high specific surface area and excellent heat resistance is preferred. In order to improve heat resistance, a rare earth such as cerium (Ce) or lanthanum (La), barium (Ba), or the like may be used.
本発明の請求項２に記載の発明は、ＣｓＶ酸化物が、Ｃｓ2Ｖ4Ｏ11であることを特徴とする請求項１記載の排ガス浄化触媒である。
The invention according to
また、本発明の請求項３に記載の発明は、アルカリ金属の硫酸塩を含むことを特徴とする請求項１または２記載の排ガス浄化触媒である。
The invention according to
Ｃｓ2Ｖ4Ｏ11は、種々あるＣｓＶ酸化物の中では融点が低い（４４６℃）にも関わらず、Ｃｓを含む硫酸塩の共存下で８００℃以上の高温に曝されても安定して存在できる。それと同時に、硫酸塩の共存下においてもＰＭに対して高い酸素供給能力を発揮し、十分なＰＭ燃焼性能を発揮できる。 Although Cs 2 V 4 O 11 has a low melting point (446 ° C.) among various CsV oxides, Cs 2 V 4 O 11 is stable even when exposed to a high temperature of 800 ° C. or higher in the presence of a sulfate containing Cs. Can exist. At the same time, even in the presence of sulfate, it exhibits a high oxygen supply capacity for PM and can exhibit sufficient PM combustion performance.
また、ＣｓＶ酸化物の融点は、低いものは４００℃以下である一方、Ｃｓを含む硫酸塩はいずれも融点が高く、例えば硫酸セシウム（Ｃｓ2ＳＯ4）の融点は１０１０℃である。このような硫酸塩はＣｓＶ酸化物と共存すると、硫酸塩とＣｓＶ酸化物とが共晶混合物を形成し、硫酸塩は本来より低い温度で溶融する。しかし、硫酸塩自体は本来熱に対して安定であるので、これが共存することでＣｓＶ酸化物の移動や蒸散を抑制できる。 The low melting point of CsV oxide is 400 ° C. or lower, while the sulfate containing Cs has a high melting point. For example, cesium sulfate (Cs 2 SO 4 ) has a melting point of 1010 ° C. When such a sulfate coexists with the CsV oxide, the sulfate and the CsV oxide form a eutectic mixture, and the sulfate melts at a temperature lower than the original temperature. However, since the sulfate itself is inherently stable to heat, the coexistence of the sulfate can suppress the migration and transpiration of the CsV oxide.
アルカリ金属としては上記で述べたＣｓが好ましく、ＣｓＶ酸化物中のＣｓが蒸散した場合にも、Ｃｓを含む硫酸塩が近傍に存在することでＣｓＶ酸化物側へＣｓが供給されると考えられ、ＣｓＶ酸化物の結晶構造が不可逆的に変化するのを抑制すると考えられる。 As the alkali metal, Cs described above is preferable. Even when Cs in the CsV oxide is evaporated, it is considered that Cs is supplied to the CsV oxide side due to the presence of a sulfate containing Cs in the vicinity. It is considered that the crystal structure of the CsV oxide is suppressed from irreversibly changing.
これにより、耐久性を向上した溶融塩型排ガス浄化触媒を提供することができる。 Thereby, the molten salt type exhaust gas purification catalyst with improved durability can be provided.
本発明の請求項４に記載の発明は、請求項１乃至３のいずれかに記載の排ガス浄化触媒を、セラミックス又は金属のフィルタに塗布したことを特徴とする排ガス浄化フィルタである。 According to a fourth aspect of the present invention, there is provided an exhaust gas purification filter, wherein the exhaust gas purification catalyst according to any one of the first to third aspects is applied to a ceramic or metal filter.
本発明の排ガス浄化触媒を実際に使用する場合は、セラミックス又は金属からなる耐熱性のフィルタに塗布し、排ガス経路に設置する。特にＳｉＣやコージェライト製のＤＰＦに塗布することが多い。 When the exhaust gas purification catalyst of the present invention is actually used, it is applied to a heat-resistant filter made of ceramics or metal and installed in the exhaust gas path. In particular, it is often applied to DPF made of SiC or cordierite.
これにより、耐久性を向上した溶融塩型排ガス浄化触媒をコーティングした排ガス浄化フィルタを提供することができる。 Thereby, the exhaust gas purification filter coated with the molten salt type exhaust gas purification catalyst with improved durability can be provided.
以下で実施例と比較例を用いた評価について説明する。 The evaluation using Examples and Comparative Examples will be described below.
全ての例で、触媒成分としてのＣｓＶ酸化物は、Ｃｓ2Ｖ4Ｏ11を用い、硫酸セシウム（Ｃｓ2ＳＯ4）を共存させている。触媒成分を担持する担体としては、一般に入手できる種々の担体に対して予備実験を実施し、特に下記の例に関して詳細に検討した。
（実施例１）
触媒成分を担持する担体として、比表面積約１５０ｍ2／ｇのγ−アルミナ（Ａｌ2Ｏ3）を用いた排ガス浄化触媒。
（比較例１）
触媒成分を担持する担体として、比表面積約２５０ｍ2／ｇのアナタース型チタニア（ＴｉＯ2）を用いた排ガス浄化触媒。
In all examples, the CsV oxide as the catalyst component uses Cs 2 V 4 O 11 and coexists with cesium sulfate (Cs 2 SO 4 ). As the carrier for supporting the catalyst component, preliminary experiments were conducted on various commonly available carriers, and the following examples were examined in detail.
Example 1
An exhaust gas purification catalyst using γ-alumina (Al 2 O 3 ) having a specific surface area of about 150 m 2 / g as a carrier for supporting a catalyst component.
(Comparative Example 1)
An exhaust gas purification catalyst using anatase type titania (TiO 2 ) having a specific surface area of about 250 m 2 / g as a carrier for supporting a catalyst component.
過去の研究から、本発明の触媒成分とチタニアは反応しにくいことが分かっており、意図しない不活性成分生成による触媒活性低下を抑制できる。
（比較例２）
比較例１と同じ担体で、触媒成分ごとの層を形成させた触媒。
From past studies, it has been found that the catalyst component of the present invention and titania are difficult to react, and it is possible to suppress a decrease in catalyst activity due to unintended generation of an inactive component.
(Comparative Example 2)
A catalyst in which a layer for each catalyst component is formed on the same carrier as in Comparative Example 1.
比較例２は、触媒成分の蒸散を抑制するために、担体に触媒成分を担持する際、ＣｓＶ酸化物、硫酸セシウムの順序で担持し、より表面に硫酸セシウムが配置されるよう作製した。
（比較例３）
触媒成分を担持する担体として、ＳｉＯ2ドープにより耐熱性を高めた比表面積約１５０ｍ2／ｇのアナタース型チタニアを用いた排ガス浄化触媒。
（比較例４）
触媒成分を担持する担体として、ルチル型チタニアを用いた排ガス浄化触媒。
（比較例５）
触媒成分を担持する担体として、マグネシア（ＭｇＯ）を用いた排ガス浄化触媒。
In Comparative Example 2, in order to suppress transpiration of the catalyst component, CsV oxide and cesium sulfate were supported in this order when the catalyst component was supported on the carrier, and cesium sulfate was arranged on the surface.
(Comparative Example 3)
An exhaust gas purification catalyst using anatase-type titania having a specific surface area of about 150 m 2 / g, whose heat resistance is improved by doping with SiO 2 as a carrier for supporting a catalyst component.
(Comparative Example 4)
An exhaust gas purification catalyst using rutile-type titania as a carrier for supporting a catalyst component.
(Comparative Example 5)
An exhaust gas purification catalyst using magnesia (MgO) as a carrier for supporting a catalyst component.
金属硝酸塩からなる溶融塩型触媒を担持するのに、塩基性担体が好ましいと報告されている（特許第３８２１３５７号）。比較例５は、従来技術と同様の効果を期待し、塩基性担体としてのマグネシアに、本発明の触媒成分を担持した。
＜評価例１＞
上記を用いて、（１）触媒活性と（２）触媒安定性を評価した。
（１）触媒活性の評価
ＰＭ燃焼触媒の一般的な評価方法として、熱重量／示差熱分析装置を用いて以下の実験を実施した。
It has been reported that a basic support is preferable for supporting a molten salt type catalyst composed of a metal nitrate (Japanese Patent No. 3821357). Comparative Example 5 expected the same effect as the prior art, and supported the catalyst component of the present invention on magnesia as a basic support.
<Evaluation Example 1>
Using the above, (1) catalyst activity and (2) catalyst stability were evaluated.
(1) Evaluation of catalytic activity As a general evaluation method of a PM combustion catalyst, the following experiment was performed using a thermogravimetric / differential thermal analyzer.
触媒を模擬ＰＭの活性炭と混合し、熱重量／示差熱分析装置を用いて加熱昇温した。温度上昇に伴って活性炭は燃焼して重量が減少するが、共存する触媒の作用によって燃焼の開始温度が異なる。この温度が低いことが、高い触媒活性の目安となる。
（２）触媒安定性の評価
触媒成分の蒸散が従来触媒ＤＰＦ性能低下の一因だと推測し、触媒の安定性を以下の実験による成分の蒸散度合いで評価した。
The catalyst was mixed with activated carbon of simulated PM, and the temperature was raised by heating using a thermogravimetric / differential thermal analyzer. As the temperature rises, the activated carbon burns and loses weight, but the combustion start temperature varies depending on the action of the coexisting catalyst. This low temperature is a measure of high catalyst activity.
(2) Evaluation of catalyst stability The transpiration of the catalyst component was presumed to be a cause of the decrease in the performance of the conventional catalyst DPF, and the stability of the catalyst was evaluated by the transpiration degree of the component by the following experiment.
触媒と模擬ＰＭを混合し、６００℃で加熱して、触媒反応を起こさせた。この操作を３回繰返し、試験前後の触媒重量を測定した。触媒の試験後重量を試験前重量で除して、触媒残存率を算出した。 The catalyst and simulated PM were mixed and heated at 600 ° C. to cause a catalytic reaction. This operation was repeated three times, and the catalyst weight before and after the test was measured. The catalyst residual ratio was calculated by dividing the weight of the catalyst after the test by the weight before the test.
（１）及び（２）の評価結果を図１に示す。右縦軸が燃焼開始温度を示し、図中Ｔ字のバーで示したプロットに一致する。左縦軸が触媒残存率を示し、図中棒グラフに一致する。燃焼開始温度がより低く、かつ触媒残存率がより高いものが、活性と耐久性を両立した触媒と言える。 The evaluation results of (1) and (2) are shown in FIG. The right vertical axis represents the combustion start temperature, which is consistent with the plot indicated by the T-shaped bar in the figure. The left vertical axis shows the catalyst remaining rate, which corresponds to the bar graph in the figure. A catalyst having a lower combustion start temperature and a higher catalyst remaining rate can be said to be a catalyst having both activity and durability.
（１）の評価では、チタニア系担体を用いた場合（比較例１〜４）、いずれも燃焼開始温度が低く、高い触媒活性を示した。逆に、（２）の評価では、チタニア系担体の触媒残存率は小さく、試験によって触媒の一部が失われたことが示唆された。一方、アルミナ担体を用いた触媒（実施例１）はチタニア系に比べて燃焼開始温度が高く触媒活性が低いが、残存率１００％と重量変化がなかった。 In the evaluation of (1), when a titania-based carrier was used (Comparative Examples 1 to 4), the combustion start temperature was low and all showed high catalytic activity. On the contrary, in the evaluation of (2), the catalyst residual rate of the titania-based carrier was small, and it was suggested that a part of the catalyst was lost by the test. On the other hand, the catalyst using the alumina carrier (Example 1) had a higher combustion start temperature and lower catalytic activity than the titania-based catalyst, but the residual rate was 100% and there was no change in weight.
なお、過去の研究例では塩基性担体が好ましいと報告されたが、塩基性のマグネシア担体を用いた比較例５は、燃焼開始温度が５００℃以上（活性炭のみの燃焼開始温度と同等）となり、触媒活性が発現しなかった。これは本発明の触媒成分が強い酸性を示すため、塩基性の強いマグネシアと激しく反応し、失活してしまったためだと考えられる。したがって塩基性担体は本発明の触媒成分には適さないと判断した。
＜評価例２＞
実施例１及び比較例１〜４の触媒をＤＰＦにコーティングして、触媒ＤＰＦを作製した。これらの触媒ＤＰＦに関して、実際のエンジンを用いて（３）ＰＭ燃焼速度評価と（４）耐久試験を実施した。
（３）ＰＭ燃焼速度評価
触媒ＤＰＦのＰＭ燃焼速度の一般的な評価方法として、実際のディーゼルエンジンを備えたエンジンベンチ試験装置を用いて以下の実験を実施した。
In the past research examples, it was reported that a basic carrier was preferable. However, Comparative Example 5 using a basic magnesia carrier had a combustion start temperature of 500 ° C. or higher (equivalent to the combustion start temperature of only activated carbon), No catalytic activity was expressed. This is presumably because the catalyst component of the present invention was strongly acidic and reacted vigorously with strongly basic magnesia and was deactivated. Therefore, it was judged that the basic support is not suitable for the catalyst component of the present invention.
<Evaluation Example 2>
The catalyst of Example 1 and Comparative Examples 1 to 4 was coated on DPF to prepare a catalyst DPF. With respect to these catalyst DPFs, (3) PM combustion rate evaluation and (4) durability test were carried out using an actual engine.
(3) PM combustion rate evaluation As a general evaluation method of the PM combustion rate of the catalyst DPF, the following experiment was conducted using an engine bench test apparatus equipped with an actual diesel engine.
触媒ＤＰＦにＰＭを堆積させた後、排ガス温度を５００℃に制御してＰＭを燃焼させた。試験前後のＤＰＦ重量を測定することで、単位時間当たりのＰＭ燃焼重量として、ＰＭ燃焼速度を算出した。
（４）耐久試験
触媒ＤＰＦの耐久性を簡易的に評価する方法として、エンジンベンチ試験装置を用いて以下の実験を実施した。
After depositing PM on the catalyst DPF, the exhaust gas temperature was controlled to 500 ° C. and PM was combusted. By measuring the DPF weight before and after the test, the PM burning rate was calculated as the PM burning weight per unit time.
(4) Durability Test As a method for simply evaluating the durability of the catalyst DPF, the following experiment was conducted using an engine bench test apparatus.
触媒ＤＰＦ を６５０℃と３００℃の排ガスに繰返し暴露した。このときの実測温度プロファイルを図２に示す。図２の３回の温度の上下を耐久試験１サイクルと定義し、最大８サイクルまで暴露を継続した。 The catalyst DPF was repeatedly exposed to exhaust gases at 650 ° C and 300 ° C. The actually measured temperature profile at this time is shown in FIG. The upper and lower temperatures in FIG. 2 were defined as one cycle of the durability test, and the exposure was continued up to a maximum of 8 cycles.
この耐久試験一定サイクルごとに、上記（３）の方法でＰＭ燃焼速度を評価した。その結果を、図３に示す。 The PM burning rate was evaluated by the above method (3) for each constant cycle of the durability test. The result is shown in FIG.
評価の結果、アルミナ担体を採用した実施例１の触媒は、初期性能低下が１９％とやや大きいものの、繰返し耐久試験を行っても高い性能を維持した。 As a result of the evaluation, the catalyst of Example 1 employing an alumina carrier maintained a high performance even after repeated durability tests, although the initial performance degradation was a little as 19%.
一方、チタニア系担体を採用した比較例１、２、４の触媒は、耐久試験による性能低下が下げ止まらなかった。また比較例３の触媒は、粉末での評価結果とは大きく乖離し、性能が非常に低かった。 On the other hand, in the catalysts of Comparative Examples 1, 2, and 4 employing the titania-based carrier, the performance deterioration due to the durability test could not be stopped. In addition, the catalyst of Comparative Example 3 was significantly different from the evaluation results with powder, and the performance was very low.
＜評価例３＞
次に、実施例１の触媒粒子の断面を走査透過型電子顕微鏡（ＳＴＥＭ：Ｓｃａｎｎｉｎｇ Ｔｒａｎｓｍｉｓｓｉｏｎ Ｅｌｅｃｔｒｏｎ Ｍｉｃｒｏｓｃｏｐｅ）で観察した。同時に、エネルギー分散Ｘ線分光法（ＥＤＸ：Ｅｎｅｒｇｙ Ｄｉｓｐｅｒｓｉｖｅ Ｘ−ｒａｙ Ｓｐｅｃｔｒｏｍｅｔｒｙ）で元素分布を測定した。ＳＴＥＭ像及び、触媒成分を代表してＶマッピング像を、図４（ａ）、（ｂ）に示す。
<Evaluation Example 3>
Next, the cross section of the catalyst particles of Example 1 was observed with a scanning transmission electron microscope (STEM). At the same time, element distribution was measured by energy dispersive X-ray spectroscopy (EDX: Energy Dispersive X-ray Spectrometry). 4A and 4B show a STEM image and a V mapping image representative of the catalyst component.
図４（ｂ）では、触媒成分のＶがナノレベルでアルミナ担体に分散している様子が分かり、触媒成分がアルミナ担体に固溶分散している可能性が示唆される。 In FIG. 4 (b), it can be seen that V of the catalyst component is dispersed on the alumina support at the nano level, suggesting the possibility that the catalyst component is dissolved and dispersed in the alumina support.
この担体に固溶分散した触媒構造が、高活性を維持しながらも、触媒成分の蒸散を抑え、極めて高い耐久性を実現したと推定される。 It is presumed that the catalyst structure solid-dispersed in this carrier suppressed the transpiration of the catalyst component while maintaining high activity and realized extremely high durability.
以上のように、ＣｓＶ酸化物触媒の活性と耐久性の両立という、相矛盾する極めて難しい課題を解決するため、触媒と担体の相互作用に着目し、アルミナ系担体と強く結合したＣｓＶ酸化物触媒が、高活性と高耐久性を両立することを見出し、従来の溶融塩型触媒に比べて耐久性を向上することができた。 As described above, in order to solve the extremely difficult problem of conflicting activity and durability of the CsV oxide catalyst, paying attention to the interaction between the catalyst and the carrier, the CsV oxide catalyst strongly bonded to the alumina carrier. However, it was found that both high activity and high durability were achieved, and the durability could be improved as compared with conventional molten salt type catalysts.
本発明にかかる排ガス浄化触媒及び排ガス浄化フィルタは、白金族金属不使用で、かつ従来の溶融塩型触媒に比べて耐久性を向上したものであるので、ディーゼルエンジンからの排ガスを浄化する触媒ＤＰＦ等として有用である。 The exhaust gas purification catalyst and the exhaust gas purification filter according to the present invention do not use a platinum group metal and have improved durability as compared with the conventional molten salt type catalyst. Useful as such.
Claims (3)
前記セシウムとバナジウムの複合金属酸化物が、Ｃｓ ２ Ｖ ４ Ｏ １１ であり、
前記アルミナは、比表面積が約１５０ｍ ２ ／ｇのγ−アルミナであることを特徴とする排ガス浄化触媒。 Cesium and the composite metal oxide of vanadium, alumina as a carrier for carrying the mixed metal oxides of the cesium and vanadium seen including,
The composite metal oxide of cesium and vanadium is Cs 2 V 4 O 11 ,
The exhaust gas purifying catalyst , wherein the alumina is γ-alumina having a specific surface area of about 150 m 2 / g .
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