JP2010030823A - Compound oxide and catalyst containing the compound oxide for cleaning exhaust gas - Google Patents
Compound oxide and catalyst containing the compound oxide for cleaning exhaust gas Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 69
- 150000001875 compounds Chemical class 0.000 title abstract 4
- 238000004140 cleaning Methods 0.000 title abstract 2
- 239000013078 crystal Substances 0.000 claims abstract description 48
- 239000007789 gas Substances 0.000 claims abstract description 41
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000001301 oxygen Substances 0.000 claims abstract description 17
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 17
- 229910052763 palladium Inorganic materials 0.000 claims abstract description 15
- 230000007547 defect Effects 0.000 claims abstract description 14
- 229910052742 iron Inorganic materials 0.000 claims abstract description 14
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 13
- 229910052703 rhodium Inorganic materials 0.000 claims abstract description 13
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 12
- 229910052741 iridium Inorganic materials 0.000 claims abstract description 12
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 12
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 12
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 12
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 12
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 11
- 229910052707 ruthenium Inorganic materials 0.000 claims abstract description 11
- 239000002131 composite material Substances 0.000 claims description 32
- 238000000746 purification Methods 0.000 claims description 30
- 229910052751 metal Inorganic materials 0.000 claims description 26
- 239000002184 metal Substances 0.000 claims description 26
- 230000003197 catalytic effect Effects 0.000 claims description 7
- 230000003647 oxidation Effects 0.000 claims description 6
- 238000007254 oxidation reaction Methods 0.000 claims description 6
- 229910014211 My O Inorganic materials 0.000 claims 1
- 239000000203 mixture Substances 0.000 abstract description 9
- 239000000843 powder Substances 0.000 description 24
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 23
- 238000000034 method Methods 0.000 description 22
- 230000000052 comparative effect Effects 0.000 description 18
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 14
- 229910052712 strontium Inorganic materials 0.000 description 6
- DHEQXMRUPNDRPG-UHFFFAOYSA-N strontium nitrate Chemical compound [Sr+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O DHEQXMRUPNDRPG-UHFFFAOYSA-N 0.000 description 6
- IATRAKWUXMZMIY-UHFFFAOYSA-N strontium oxide Chemical compound [O-2].[Sr+2] IATRAKWUXMZMIY-UHFFFAOYSA-N 0.000 description 6
- 238000002441 X-ray diffraction Methods 0.000 description 5
- 230000032683 aging Effects 0.000 description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 5
- 239000012153 distilled water Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 229910052761 rare earth metal Inorganic materials 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910002651 NO3 Inorganic materials 0.000 description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 230000002950 deficient Effects 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 229910052723 transition metal Inorganic materials 0.000 description 3
- 150000003624 transition metals Chemical class 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 150000004703 alkoxides Chemical class 0.000 description 2
- 150000001860 citric acid derivatives Chemical class 0.000 description 2
- 238000000975 co-precipitation Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
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- 210000004027 cell Anatomy 0.000 description 1
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- 229910052878 cordierite Inorganic materials 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
- 238000011156 evaluation Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 1
- SZQUEWJRBJDHSM-UHFFFAOYSA-N iron(3+);trinitrate;nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O SZQUEWJRBJDHSM-UHFFFAOYSA-N 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 150000004690 nonahydrates Chemical class 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
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- 238000003756 stirring Methods 0.000 description 1
- 238000012916 structural analysis Methods 0.000 description 1
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
Description
本発明は、複合酸化物及び同複合酸化物を含有した排気ガス浄化用触媒に関する。 The present invention relates to a composite oxide and an exhaust gas purifying catalyst containing the composite oxide.
ガソリンエンジン用の三元触媒では、エンジン始動直後の温度が低いときから排気ガスを浄化することができるように、従来よりPd担持アルミナ系の触媒成分が広く利用されている。しかし、Pd担持アルミナの場合、高温の排気ガスに晒されると、該排気ガスの熱によってPdの凝集(シンタリング)を生じて劣化し易い。 In a three-way catalyst for a gasoline engine, a Pd-supported alumina-based catalyst component has been widely used in the past so that exhaust gas can be purified when the temperature immediately after the engine is started is low. However, in the case of Pd-supported alumina, when exposed to high-temperature exhaust gas, Pd agglomeration (sintering) is likely to occur due to the heat of the exhaust gas, and the Pd-supported alumina is likely to deteriorate.
これに対して、Pdの凝集を抑制すべく、該Pdをペロブスカイト型複合酸化物の結晶内に固溶させた触媒材が知られている。例えば、特許文献1には、ABPdO3の一般式(式中、Aは、3価以外に価数変動しない希土類元素を必ず含み、かつ、3価より小さい価数をとり得る希土類元素を含まない希土類元素から選ばれる少なくとも1種の元素を示し、Bは、Co、Pd、希土類元素以外の遷移元素およびAlから選ばれる少なくとも1種の元素を示す。)で表されるペロブスカイト型構造の複合酸化物を含む排ガス浄化用触媒が開示されている。これに関連して、LaFe0.98Pd0.02O3+δのペロブスカイト型複合酸化物を含有する触媒も実用化されており、排気ガス雰囲気がリーンの状態ではPdが結晶粒子内に固溶し、リッチの状態では結晶粒子表面に析出するため、Pdの粒成長が抑制される、と謳われている。
しかし、上記LaFe0.98Pd0.02O3+δのペロブスカイト型複合酸化物について調べたところ、その耐熱性は比較的高いものの、触媒としての使用開始初期(長期に亘る熱履歴を受けていない状態)であっても、HC(炭化水素)浄化に関するライトオフ性能や高温でのNOx浄化性能はそれほど高くはなく、排気ガス浄化性能を高めるには、触媒金属としてRhやPtを比較的多量に使用しなければならないことがわかった。 However, when the perovskite type complex oxide of LaFe 0.98 Pd 0.02 O 3 + δ was examined, its heat resistance was relatively high, but it was initially used as a catalyst (not subjected to a long-term thermal history). However, the light-off performance related to HC (hydrocarbon) purification and the NOx purification performance at high temperatures are not so high. To improve the exhaust gas purification performance, a relatively large amount of Rh or Pt is used as the catalyst metal. I knew I had to do it.
すなわち、本発明の課題は、少ない触媒金属量でも高い排気ガス浄化性能が得られるようにすることにある。 That is, an object of the present invention is to obtain high exhaust gas purification performance even with a small amount of catalytic metal.
本発明は、このような課題を解決するために、Ruddlesden-Popper型結晶相とペロブスカイト型結晶相とが混在した複合酸化物に触媒金属を組み合わせるようにした。 In the present invention, in order to solve such problems, a catalyst metal is combined with a composite oxide in which a Ruddlesden-Popper type crystal phase and a perovskite type crystal phase are mixed.
すなわち、請求項1に係る発明は、一般式Sr3T2−xMxO7−δで表されるRuddlesden-Popper型結晶相と、一般式SrT1−yMyO3−δで表されるペロブスカイト型結晶相とが混在し、
上記各一般式において、xは0≦x<0.1を満たす数であり、yは0≦y<0.1を満たす数であり、δは酸素欠陥分であり、TはFe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種であり、MはPd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種であることを特徴とする複合酸化物である。
That is, Table invention, the general formula Sr 3 T 2-x M x O and Ruddlesden-Popper type crystal phase represented by the 7-[delta], the general formula SrT 1-y M y O 3 -δ according to claim 1 Perovskite-type crystal phase to be mixed,
In the above general formulas, x is a number satisfying 0 ≦ x <0.1, y is a number satisfying 0 ≦ y <0.1, δ is an oxygen defect component, T is Fe, Mo, Complex oxidation characterized in that it is at least one selected from Zr, Ti, V, Cr, Mn and Co, and M is at least one selected from Pd, Ru, Rh, Pt and Ir. It is a thing.
請求項2に係る発明は、請求項1に記載された複合酸化物を含有することを特徴とする排気ガス浄化用触媒である。
An invention according to
請求項3に係る発明は、一般式Sr3T2O7−δで表されるRuddlesden-Popper型結晶相と、一般式SrTO3−δで表されるペロブスカイト型結晶相とが混在した複合酸化物(式中、TはFe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種であり、δは酸素欠陥分である。)に、Pd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種の触媒金属Mが担持されてなる触媒成分を含有することを特徴とする排気ガス浄化用触媒である。 The invention according to claim 3 is a composite oxidation in which a Ruddlesden-Popper type crystal phase represented by a general formula Sr 3 T 2 O 7-δ and a perovskite type crystal phase represented by a general formula SrTO 3-δ are mixed. (Wherein T is at least one selected from Fe, Mo, Zr, Ti, V, Cr, Mn and Co, and δ is an oxygen defect), Pd, Ru, Rh, An exhaust gas purification catalyst comprising a catalyst component on which at least one catalyst metal M selected from Pt and Ir is supported.
以上の各発明の複合酸化物は、Srと、Fe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種の金属Tとを成分として有する酸素欠陥型のRuddlesden-Popper型結晶相と、同じく、Srと、Fe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種の金属Tとを成分として有する酸素欠陥型のペロブスカイト型結晶相とが混在したものである点で共通する。 The composite oxide of each of the above inventions is an oxygen-deficient Ruddlesden- having Sr and at least one metal T selected from Fe, Mo, Zr, Ti, V, Cr, Mn and Co as components. Similarly to the popper type crystal phase, oxygen-deficient perovskite type crystal phase having Sr and at least one metal T selected from Fe, Mo, Zr, Ti, V, Cr, Mn and Co as components. And are common in that they are mixed.
そうして、このような複合酸化物を構成要素とすることにより、本発明によれば、排気ガス中のHCやCOの酸化浄化及びNOxの還元浄化が効率良く進む。遷移金属Tの価数変化によって生ずる酸素欠陥が排気ガスを浄化する活性点となり、優れた排気ガス浄化性能が得られると考えられる。特に、遷移金属TがFeである場合、Fe4+の異常原子価をとり、上記Ruddlesden-Popper型結晶相及びペロブスカイト型結晶相各々において、その価数変化によって生ずる酸素欠陥が活性点となることから、高い触媒活性が得られる。Coの場合も、Co4+の異常原子価をとり得ることから、Feの場合と同様の効果が得られる。 Thus, by using such a complex oxide as a constituent element, according to the present invention, oxidation purification of HC and CO in exhaust gas and reduction purification of NOx proceed efficiently. It is considered that an oxygen defect caused by a change in the valence of the transition metal T becomes an active point for purifying the exhaust gas, and excellent exhaust gas purification performance can be obtained. In particular, when the transition metal T is Fe, it takes an abnormal valence of Fe 4+ , and oxygen defects caused by the valence change become active sites in each of the Ruddlesden-Popper type crystal phase and the perovskite type crystal phase. High catalytic activity can be obtained. In the case of Co as well, since the anomalous valence of Co 4+ can be obtained, the same effect as in the case of Fe can be obtained.
また、請求項1,2に係る発明の場合、上記Ruddlesden-Popper型結晶相及びペロブスカイト型結晶相各々において、Pd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種の金属Mが上記金属Tの一部に置換して配置されると、上記酸素欠陥による活性点と、当該金属M(触媒金属)との働きにより、さらに優れた排気ガス浄化性能が得られる。
In the inventions according to
また、請求項3に係る発明の場合、遷移金属Tの価数変化によって当該複合酸化物の結晶に生ずる酸素欠陥(活性点)と、該複合酸化物に担持されたPd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種の触媒金属Mとの働きにより、優れた排気ガス浄化性能が得られる。 In the case of the invention according to claim 3, oxygen defects (active points) generated in the crystal of the composite oxide due to the valence change of the transition metal T, and Pd, Ru, Rh, Pt supported on the composite oxide And exhaust gas purifying performance can be obtained by the action of at least one catalyst metal M selected from Ir and Ir.
以上のように、本発明によれば、Srと、Fe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種の金属Tとを成分として有する酸素欠陥型のRuddlesden-Popper型結晶相と、同じく、Srと、Fe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種の金属Tとを成分として有する酸素欠陥型のペロブスカイト型結晶相とが混在した複合酸化物を構成要素としており、かかる複合酸化物と、Pd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種の金属Mとを組み合わせたことにより、排気ガス中のHCやCOの酸化浄化及びNOxの還元浄化を効率良く行うことができる。 As described above, according to the present invention, oxygen-deficient Ruddlesden having Sr and at least one metal T selected from Fe, Mo, Zr, Ti, V, Cr, Mn, and Co as components. -Popper type crystal phase, oxygen defect type perovskite type crystal having Sr and at least one metal T selected from Fe, Mo, Zr, Ti, V, Cr, Mn and Co as components In the exhaust gas, a composite oxide in which phases are mixed is used as a constituent element, and the composite oxide is combined with at least one metal M selected from Pd, Ru, Rh, Pt and Ir. Thus, oxidation purification of HC and CO and reduction purification of NOx can be performed efficiently.
以下、本発明の実施形態を図面に基づいて説明する。尚、以下の好ましい実施形態の説明は、本質的に例示に過ぎず、本発明、その適用物或いはその用途を制限することを意図するものではない。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.
<実施形態1>
本実施形態に係る複合酸化物は、一般式Sr3T2−xMxO7−δで表されるRuddlesden-Popper型結晶相と、一般式SrT1−yMyO3−δで表されるペロブスカイト型結晶相とが混在する。
<Embodiment 1>
The composite oxide according to this embodiment includes a Ruddlesden-Popper type crystal phase represented by a general formula Sr 3 T 2−x M x O 7−δ and a general formula SrT 1−y M y O 3−δ . Perovskite type crystal phase mixed.
上記Ruddlesden-Popper型結晶相の一般式Sr3T2−xMxO7−δにおいて、xは0≦x<0.1を満たす数であり、δは酸素欠陥分である。TはFe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種であり、MはPd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種である。 In the general formula Sr 3 T 2-x M x O 7-δ of the Ruddlesden-Popper type crystal phase, x is a number satisfying 0 ≦ x <0.1, and δ is an oxygen defect component. T is at least one selected from Fe, Mo, Zr, Ti, V, Cr, Mn, and Co, and M is at least one selected from Pd, Ru, Rh, Pt, and Ir.
x=0、すなわち、金属Mを含有しないSr3T2O7−δのRuddlesden-Popper型結晶相であってもよいが、金属Mは触媒活性を高める働きをすることから、金属Mの原子割合xは0.01以上とすることが好ましい。但し、原子割合xが0.1以上になると、金属Mは当該複合酸化物に固溶し難くなり、また、コスト的にも不利になる。 x = 0, that is, a Ruddlesden-Popper type crystal phase of Sr 3 T 2 O 7-δ that does not contain metal M, but metal M functions to enhance catalytic activity. The ratio x is preferably 0.01 or more. However, when the atomic ratio x is 0.1 or more, the metal M is difficult to dissolve in the composite oxide, and the cost is disadvantageous.
上記ペロブスカイト型結晶相の一般式SrT1−yMyO3−δにおいて、yは0≦y<0.1を満たす数であり、δは酸素欠陥分である。TはFe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種であり、MはPd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種である。 In the general formula SrT 1-y M y O 3-δ of the perovskite crystal phase, y is a number satisfying 0 ≦ y <0.1, and δ is an oxygen defect component. T is at least one selected from Fe, Mo, Zr, Ti, V, Cr, Mn, and Co, and M is at least one selected from Pd, Ru, Rh, Pt, and Ir.
y=0、すなわち、金属Mを含有しないSrTO3−δのペロブスカイト型結晶相であってもよいが、金属Mは触媒活性を高める働きをすることから、金属Mの原子割合xは0.01以上とすることが好ましい。但し、原子割合xが0.1以上になると、金属Mは当該複合酸化物に固溶し難くなり、また、コスト的にも不利になる。 Although y = 0, that is, a perovskite crystal phase of SrTO 3-δ that does not contain metal M, metal M functions to enhance the catalytic activity, and therefore the atomic ratio x of metal M is 0.01. The above is preferable. However, when the atomic ratio x is 0.1 or more, the metal M is difficult to dissolve in the composite oxide, and the cost is disadvantageous.
上記Ruddlesden-Popper型結晶相とペロブスカイト型結晶相とが混在する複合酸化物は、共沈法、クエン酸錯体法、アルコキシド法など、公知の方法によって製造することができる。また、当該複合酸化物を排気ガス浄化用触媒に用いる場合、ハニカム担体に当該複合酸化物を含有する触媒層を形成すればよい。この複合酸化物には、さらにPd、Pt、Rh等の触媒金属を含浸法や蒸発乾固法等によって担持させることができる。また、この複合酸化物と他の触媒成分(例えば、Pt担持アルミナ)とを混合して触媒層に配置することができる。 The composite oxide in which the Ruddlesden-Popper type crystal phase and the perovskite type crystal phase are mixed can be produced by a known method such as a coprecipitation method, a citric acid complex method, or an alkoxide method. When the composite oxide is used as an exhaust gas purification catalyst, a catalyst layer containing the composite oxide may be formed on the honeycomb carrier. This composite oxide can further carry a catalytic metal such as Pd, Pt, Rh, etc. by an impregnation method, an evaporation to dryness method, or the like. Further, this composite oxide and other catalyst components (for example, Pt-supported alumina) can be mixed and disposed in the catalyst layer.
<実施形態2>
本実施形態に係る複合酸化物は、一般式Sr3T2O7−δで表されるRuddlesden-Popper型結晶相と、一般式SrTO3−δで表されるペロブスカイト型結晶相とが混在する。両一般式中、TはFe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種であり、δは酸素欠陥分である。そして、本実施形態に係る排気ガス浄化用触媒は、上記混相の複合酸化物に、Pd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種の触媒金属Mが担持されてなる触媒成分を含有することを特徴とする。
<
In the composite oxide according to the present embodiment, a Ruddlesden-Popper type crystal phase represented by a general formula Sr 3 T 2 O 7-δ and a perovskite type crystal phase represented by a general formula SrTO 3-δ are mixed. . In both general formulas, T is at least one selected from Fe, Mo, Zr, Ti, V, Cr, Mn and Co, and δ is an oxygen defect component. The exhaust gas purifying catalyst according to the present embodiment is a catalyst component in which at least one catalyst metal M selected from Pd, Ru, Rh, Pt and Ir is supported on the mixed phase composite oxide. It is characterized by containing.
上記Ruddlesden-Popper型結晶相とペロブスカイト型結晶相とが混在する複合酸化物は、共沈法、クエン酸錯体法、アルコキシド法など、公知の方法によって製造することができる。触媒金属Mは、含浸法や蒸発乾固法等によって上記複合酸化物に担持させることができる。この複合酸化物を排気ガス浄化用触媒に用いる場合、ハニカム担体に当該複合酸化物を含有する触媒層を形成すればよい。この複合酸化物と他の触媒成分(例えば、Pt担持アルミナ)とを混合して触媒層に配置することができる。 The composite oxide in which the Ruddlesden-Popper type crystal phase and the perovskite type crystal phase are mixed can be produced by a known method such as a coprecipitation method, a citric acid complex method, or an alkoxide method. The catalytic metal M can be supported on the composite oxide by an impregnation method, an evaporation to dryness method, or the like. When this composite oxide is used as an exhaust gas purification catalyst, a catalyst layer containing the composite oxide may be formed on the honeycomb carrier. This composite oxide and other catalyst components (for example, Pt-supported alumina) can be mixed and disposed in the catalyst layer.
<実施例及び比較例>
以下、自動車の排気ガス浄化用触媒に関する実施例及び比較例について説明する。
<Examples and Comparative Examples>
Examples and comparative examples relating to automobile exhaust gas purification catalysts will be described below.
[触媒の調製]
−実施例1−
硝酸ストロンチウム(無水)31.7g、硝酸鉄(III)九水和物39.6g、硝酸Pd溶液(Pd=4.362質量%)4.9g、クエン酸(無水)96.1gを蒸留水に入れて攪拌した後、加熱して溶媒を除去することにより、Sr、Fe及びPdのクエン酸錯体の混合物を得た。このクエン酸錯体混合物を、大気中において、400℃の温度に2時間加熱保持する仮焼成を行なった後、1000℃の温度に6時間加熱保持する本焼成を行なった。得られた焼成品を粉砕して触媒粉末を得た。この触媒粉末の組成式は、Sr3Fe1.96Pd0.04O7−δである。
[Preparation of catalyst]
Example 1
31.7 g of strontium nitrate (anhydrous), 39.6 g of iron (III) nitrate nonahydrate, 4.9 g of Pd nitrate solution (Pd = 4.362% by mass), and 96.1 g of citric acid (anhydrous) in distilled water The mixture was stirred and then heated to remove the solvent to obtain a mixture of Sr, Fe and Pd citrate complexes. This citric acid complex mixture was calcined in the air at a temperature of 400 ° C. for 2 hours and then calcined at a temperature of 1000 ° C. for 6 hours. The obtained fired product was pulverized to obtain a catalyst powder. The composition formula of this catalyst powder is Sr 3 Fe 1.96 Pd 0.04 O 7-δ .
上記触媒粉末について、XRD(X線回折)分析装置による構造解析を行なった。図1はそのXRDチャートである。図1の白丸を付した各回折角度のピーク、特に回折角度42度のピークはRuddlesden-Popper型結晶のSr3Fe2O7で現れ、黒塗り三角を付した各回折角度のピーク、特に回折角度40.5度のピークはペロブスカイト型結晶のSrFeO3で現れることが知られている。一方、図1のXRDチャートには、Pd及びその酸化物を示すピークは現れていない。そうして、上記触媒粉末の場合は、微量のPdを含有するところ、そのPdは、そのイオン半径がFeのイオン半径に近いことから、Feの一部に置換して当該複合酸化物に固溶していると考えられる。 The catalyst powder was subjected to structural analysis using an XRD (X-ray diffraction) analyzer. FIG. 1 is an XRD chart thereof. The peak of each diffraction angle marked with a white circle in FIG. 1, particularly the peak at a diffraction angle of 42 degrees, appears in Ruddlesden-Popper type crystal Sr 3 Fe 2 O 7 , and the peak of each diffraction angle marked with a black triangle, especially diffraction. It is known that a peak at an angle of 40.5 degrees appears in SrFeO 3 of a perovskite crystal. On the other hand, the peak indicating Pd and its oxide does not appear in the XRD chart of FIG. Thus, in the case of the above catalyst powder, a small amount of Pd is contained. Since the ionic radius of the Pd is close to the ionic radius of Fe, the Pd is solidified in the composite oxide by substituting part of Fe. It is thought that it is melted.
従って、図1の白丸を付けた各ピークは、微量のPdが固溶したRuddlesden-Popper型結晶のSr3Fe2−xPdxO7−δによるものであるということでき、黒塗り三角を付けた各ピークは、微量のPdが固溶したペロブスカイト型結晶のSrFe1−yPdyO3−δによるものであるということができる。すなわち、上記触媒粉末は、Sr3Fe2−xPdxO7−δのRuddlesden-Popper型結晶相と、SrFe1−yPdyO3−δのペロブスカイト型結晶相とが混在した混相の複合酸化物粉末である。 Accordingly, it can be said that each peak with white circles in FIG. 1 is due to Sr 3 Fe 2−x Pd x O 7−δ of Ruddlesden-Popper type crystal in which a small amount of Pd is dissolved, and a black triangle is shown. Each attached peak can be said to be due to SrFe 1-y Pd y O 3-δ of a perovskite crystal in which a small amount of Pd is dissolved. That is, the catalyst powder is a composite of a mixed phase in which a Ruddlesden-Popper type crystal phase of Sr 3 Fe 2-x Pd x O 7-δ and a perovskite type crystal phase of SrFe 1-y Pd y O 3-δ are mixed. It is an oxide powder.
この実施例1では、Pd溶液を複合酸化物の原料に添加することにより、Pdを該複合酸化物の結晶に固溶させており、このようなPd担持法を以下ではドープ法と呼ぶ。 In this Example 1, Pd solution is added to the complex oxide raw material to dissolve Pd in the complex oxide crystal. Such a Pd support method is hereinafter referred to as a dope method.
上記触媒粉末及びZrO2バインダー各々を所定量秤量し、蒸留水を加えてスラリーを調製した。これに、コージェライト製ハニカム担体(セル壁厚4mil(101.6×10−3mm)、1平方インチ(645.16mm2)当たりのセル数400)を浸漬し、Pd担持量が担体1L当たり0.98gとなるように余分なスラリーを加圧エアーで吹き飛ばした後、大気中において500℃の温度に2時間加熱保持する焼成を行なった。以上により、ハニカム担体上に上記触媒粉末を含有する触媒層が形成された排気ガス浄化用触媒を得た。 A predetermined amount of each of the catalyst powder and ZrO 2 binder was weighed, and distilled water was added to prepare a slurry. A cordierite honeycomb carrier (cell wall thickness 4 mil (101.6 × 10 −3 mm), 400 cells per square inch (645.16 mm 2 )) was immersed in this, and the amount of Pd supported was 1 L per carrier. Excess slurry was blown off with pressurized air so that the amount became 0.98 g, followed by firing in the atmosphere at a temperature of 500 ° C. for 2 hours. As a result, an exhaust gas purifying catalyst having a catalyst layer containing the catalyst powder formed on the honeycomb carrier was obtained.
−実施例2−
硝酸ストロンチウム(無水)31.7g、硝酸鉄(III)九水和物40.4g、クエン酸(無水)96.1gを蒸留水に入れて攪拌した後、加熱して溶媒を除去することにより、Sr及びFeのクエン酸錯体の混合物を得た。このクエン酸錯体混合物を、大気中において、400℃の温度に2時間加熱保持する仮焼成を行なった後、1000℃の温度に6時間加熱保持する本焼成を行なった。得られた焼成品(複合酸化物)を粉砕し、これにPd量が実施例1と同量になるよう硝酸Pd溶液を加え、蒸発乾固法でPdを当該粉末に担持し、大気中で500℃の温度に2時間保持する焼成を行なうことにより、本実施例に係る触媒粉末を得た。この触媒粉末は、Sr3Fe2O7−δのRuddlesden-Popper型結晶相と、SrFeO3−δのペロブスカイト型結晶相とが混在した混相の複合酸化物にPdが担持されたものである。
-Example 2-
By stirring 31.7 g of strontium nitrate (anhydrous), 40.4 g of iron nitrate (III) nonahydrate, and 96.1 g of citric acid (anhydrous) in distilled water, the solvent is removed by heating. A mixture of citrate complexes of Sr and Fe was obtained. This citric acid complex mixture was calcined in the air at a temperature of 400 ° C. for 2 hours and then calcined at a temperature of 1000 ° C. for 6 hours. The fired product (composite oxide) obtained was pulverized, and a Pd nitrate solution was added to the Pd content to be the same as in Example 1, and Pd was supported on the powder by evaporation to dryness. The catalyst powder which concerns on a present Example was obtained by performing the baking hold | maintained at the temperature of 500 degreeC for 2 hours. In this catalyst powder, Pd is supported on a mixed oxide of a mixed phase in which a Ruddlesden-Popper type crystal phase of Sr 3 Fe 2 O 7-δ and a perovskite type crystal phase of SrFeO 3-δ are mixed.
この実施例では、複合酸化物を調製した後に、これにPdを担持させたから、このようなPd担持法を以下では後担持法と呼ぶ。 In this example, after the composite oxide was prepared, Pd was supported thereon, so such a Pd supporting method is hereinafter referred to as a post-supporting method.
そうして、上記触媒粉末及びZrO2バインダー各々を所定量秤量し、実施例1と同じ条件及び方法で、ハニカム担体上に上記触媒粉末を含有する触媒層が形成された排気ガス浄化用触媒を得た。Pd担持量は実施例1と同じく0.98g/Lである。 Then, a predetermined amount of each of the catalyst powder and the ZrO 2 binder was weighed, and an exhaust gas purification catalyst in which a catalyst layer containing the catalyst powder was formed on the honeycomb carrier under the same conditions and method as in Example 1. Obtained. The amount of Pd supported is 0.98 g / L as in Example 1.
−比較例1−
酸化ストロンチウム15.5g、酸化鉄(III)8.0g、硝酸Pd溶液(Pd=4.362質量%)4.9gを蒸留水に入れて攪拌した後、加熱して溶媒を除去した(蒸発乾固)。次いで、大気中において500℃の温度に2時間保持する焼成を行なった。得られた焼成品を粉砕して触媒粉末を得た。この触媒粉末は、Pdを担持したSrOと、Pdを担持したFe2O3との混合物であり、SrO:Fe2O3=3:1(モル比)である。この比較例1では、酸化ストロンチウム及び酸化鉄の各粉末にPdを担持させたから、そのPd担持法は後担持法ということができる。
-Comparative Example 1-
15.5 g of strontium oxide, 8.0 g of iron (III) oxide, and 4.9 g of a Pd nitrate solution (Pd = 4.362% by mass) were placed in distilled water and stirred, and then heated to remove the solvent (evaporated to dryness). Hard). Next, firing was performed in the air at a temperature of 500 ° C. for 2 hours. The obtained fired product was pulverized to obtain a catalyst powder. This catalyst powder is a mixture of SrO supporting Pd and Fe 2 O 3 supporting Pd, and SrO: Fe 2 O 3 = 3: 1 (molar ratio). In Comparative Example 1, since Pd is supported on each powder of strontium oxide and iron oxide, the Pd supporting method can be called a post-supporting method.
そうして、上記触媒粉末及びZrO2バインダー各々を所定量秤量し、実施例1と同じ条件及び方法で、ハニカム担体上に上記触媒粉末を含有する触媒層が形成された排気ガス浄化用触媒を得た。Pd担持量は実施例1と同じく0.98g/Lである。 Then, a predetermined amount of each of the catalyst powder and the ZrO 2 binder was weighed, and an exhaust gas purification catalyst in which a catalyst layer containing the catalyst powder was formed on the honeycomb carrier under the same conditions and method as in Example 1. Obtained. The amount of Pd supported is 0.98 g / L as in Example 1.
−比較例2−
実施例1の硝酸ストロンチウムに代えて、硝酸ランタンを43.3gとし、他は実施例1と同じ条件で触媒粉末の調製及び排気ガス浄化用触媒の調製を行なった。比較例2の触媒粉末は、LaFe0.98Pd0.02O3のペロブスカイト型結晶構造の複合酸化物粉末である。Pd担持量は実施例1と同じく0.98g/Lである。この比較例2のPd担持法はドープ法である。
-Comparative Example 2-
In place of the strontium nitrate of Example 1, 43.3 g of lanthanum nitrate was used, and the catalyst powder and the exhaust gas purifying catalyst were prepared under the same conditions as in Example 1. The catalyst powder of Comparative Example 2 is a complex oxide powder having a perovskite crystal structure of LaFe 0.98 Pd 0.02 O 3 . The amount of Pd supported is 0.98 g / L as in Example 1. The Pd support method of Comparative Example 2 is a dope method.
上記実施例1,2及び比較例1,2の各触媒粉末の構成を表1に示す。 Table 1 shows the configurations of the catalyst powders of Examples 1 and 2 and Comparative Examples 1 and 2.
[触媒の評価]
上記実施例1,2及び比較例1,2の各排気ガス浄化用触媒について、大気中において1000℃の温度に24時間保持するエージングを行なったエージングサンプルと、このエージングを行なっていないフレッシュサンプルとを準備した。この実施例及び比較例の各サンプルをモデル排気ガス流通反応装置にセットし、排気ガス浄化性能(ライトオフ温度T50及び高温浄化率C400)を評価した。モデル排気ガスはA/F=14.7±0.9とした。すなわち、A/F=14.7のメインストリームガスを定常的に流しつつ、所定量の変動用ガスを1Hzでパルス状に添加することにより、A/Fを±0.9の振幅で強制的に振動させた。A/F=14.7、A/F=13.8及びA/F=15.6のときのガス組成を表2に示す。また、空間速度SVは60000/h、昇温速度は30℃/分とした。
[Evaluation of catalyst]
For each of the exhaust gas purifying catalysts of Examples 1 and 2 and Comparative Examples 1 and 2, an aging sample that was aged for 24 hours at a temperature of 1000 ° C. in the atmosphere, and a fresh sample that was not aged. Prepared. Each sample of this example and comparative example was set in a model exhaust gas flow reactor, and the exhaust gas purification performance (light-off temperature T50 and high temperature purification rate C400) was evaluated. The model exhaust gas was A / F = 14.7 ± 0.9. That is, the A / F is forced at an amplitude of ± 0.9 by adding a predetermined amount of fluctuation gas in a pulse form at 1 Hz while constantly flowing the main stream gas of A / F = 14.7. Vibrated. Table 2 shows the gas composition when A / F = 14.7, A / F = 13.8 and A / F = 15.6. The space velocity SV was 60000 / h, and the temperature elevation rate was 30 ° C./min.
T50は、モデル排気ガス温度の上昇により、触媒下流で検出されるガスの各成分(HC、CO及びNOx)濃度が、触媒に流入するガスの各成分(HC、CO及びNOx)濃度の半分になった時点(すなわち浄化率が50%になった時点)の触媒入口ガス温度(ライトオフ温度)であって、触媒の低温浄化性能を表すものである。C400は、触媒入口でのモデル排気ガス温度が400℃であるときのガスの各成分(HC、CO及びNOx)の浄化率であって、触媒の高温浄化性能を表すものである。 T50 indicates that the concentration of each component (HC, CO and NOx) of the gas detected downstream of the catalyst is reduced to half of the concentration of each component (HC, CO and NOx) of the gas flowing into the catalyst as the model exhaust gas temperature rises. This is the catalyst inlet gas temperature (light-off temperature) at the time when it becomes (that is, when the purification rate reaches 50%) and represents the low-temperature purification performance of the catalyst. C400 is the purification rate of each component (HC, CO and NOx) of the gas when the model exhaust gas temperature at the catalyst inlet is 400 ° C., and represents the high temperature purification performance of the catalyst.
図2は上記実施例及び比較例のフレッシュサンプルのライトオフ温度T50を示し、図3は同サンプルの高温浄化率C400を示す。T50及びC400共に、実施例1,2は比較例1,2よりも良くなっている。実施例1,2及び比較例1は、触媒粉末の構成元素の量は実質的に同じであるが、実施例1,2の排気ガス浄化性能の方が良いことから、複合酸化物にRuddlesden-Popper型結晶相とペロブスカイト型結晶相とが混在する複合酸化物を採用することが好ましいことがわかる。また、実施例1と実施例2とを比較すると、実施例1の方が良いが、これはドープによってPdを酸素欠陥に近接させたことで、NOの解離吸着が促進された効果であると推察する。 FIG. 2 shows the light-off temperature T50 of the fresh samples of the above examples and comparative examples, and FIG. 3 shows the high-temperature purification rate C400 of the samples. In both T50 and C400, Examples 1 and 2 are better than Comparative Examples 1 and 2. In Examples 1 and 2 and Comparative Example 1, the amounts of the constituent elements of the catalyst powder are substantially the same, but the exhaust gas purification performance of Examples 1 and 2 is better. Therefore, Ruddlesden- It can be seen that it is preferable to employ a composite oxide in which a popper crystal phase and a perovskite crystal phase are mixed. Further, comparing Example 1 and Example 2, Example 1 is better, but this is an effect of promoting dissociative adsorption of NO by bringing Pd close to oxygen defects by doping. I guess.
図4は上記実施例及び比較例のエージングサンプルのライトオフ温度T50を示し、図5は同サンプルの高温浄化率C400を示す。このエージング後のサンプルにおいては、CO及びNOxの高温浄化率C400(図5)に関して、実施例2と比較例1との差が殆ど見られなくなっているものの、HCの高温浄化率C400及びライトオフ温度T50(図4)に関しては、実施例1,2は比較例1,2よりも良い結果を示しており、実施例1,2に係る排気ガス浄化用触媒は耐熱性も高いということができる。 FIG. 4 shows the light-off temperature T50 of the aging samples of the above examples and comparative examples, and FIG. 5 shows the high temperature purification rate C400 of the samples. In this sample after aging, although there is almost no difference between Example 2 and Comparative Example 1 with respect to CO and NOx high temperature purification rate C400 (FIG. 5), HC high temperature purification rate C400 and light off Regarding the temperature T50 (FIG. 4), Examples 1 and 2 show better results than Comparative Examples 1 and 2, and it can be said that the exhaust gas purifying catalysts according to Examples 1 and 2 have high heat resistance. .
なし None
Claims (3)
上記各一般式において、xは0≦x<0.1を満たす数であり、yは0≦y<0.1を満たす数であり、δは酸素欠陥分であり、TはFe、Mo、Zr、Ti、V、Cr、Mn及びCoのうちから選ばれる少なくとも1種であり、MはPd、Ru、Rh、Pt及びIrのうちから選ばれる少なくとも1種であることを特徴とする複合酸化物。 A Ruddlesden-Popper type crystal phase represented by the general formula Sr 3 T 2-x M x O 7-δ and a perovskite type crystal phase represented by the general formula SrT 1- y My O 3-δ coexist. ,
In the above general formulas, x is a number satisfying 0 ≦ x <0.1, y is a number satisfying 0 ≦ y <0.1, δ is an oxygen defect component, T is Fe, Mo, Complex oxidation characterized in that it is at least one selected from Zr, Ti, V, Cr, Mn and Co, and M is at least one selected from Pd, Ru, Rh, Pt and Ir. object.
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Cited By (5)
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WO2012060174A1 (en) * | 2010-11-04 | 2012-05-10 | 日産自動車株式会社 | Layered complex oxide, oxidation catalyst, and diesel particulate filter |
JP2012217951A (en) * | 2011-04-11 | 2012-11-12 | Mazda Motor Corp | Catalyst for cleaning exhaust gas and method for producing the same |
JP6181260B1 (en) * | 2016-09-13 | 2017-08-16 | 田中貴金属工業株式会社 | Exhaust gas purification catalyst composition and exhaust gas purification catalyst |
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JP2018187621A (en) * | 2017-05-11 | 2018-11-29 | 株式会社デンソー | Nitrogen oxide occlusion material, method for producing the same, and exhaust gas purification catalyst |
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WO2012060174A1 (en) * | 2010-11-04 | 2012-05-10 | 日産自動車株式会社 | Layered complex oxide, oxidation catalyst, and diesel particulate filter |
JP5610319B2 (en) * | 2010-11-04 | 2014-10-22 | 日産自動車株式会社 | Layered complex oxide, oxidation catalyst and diesel particulate filter |
US9091195B2 (en) | 2010-11-04 | 2015-07-28 | Nissan Motor Co., Ltd. | Layered composite oxide, oxidation catalyst, and diesel particulate filter |
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JP6181260B1 (en) * | 2016-09-13 | 2017-08-16 | 田中貴金属工業株式会社 | Exhaust gas purification catalyst composition and exhaust gas purification catalyst |
JP2018043177A (en) * | 2016-09-13 | 2018-03-22 | 田中貴金属工業株式会社 | Catalyst composition for exhaust purification and catalyst for exhaust purification |
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