JP2006036556A - Inorganic oxide, exhaust gas purification catalyst support and exhaust gas purification catalyst - Google Patents
Inorganic oxide, exhaust gas purification catalyst support and exhaust gas purification catalyst Download PDFInfo
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- 229910052809 inorganic oxide Inorganic materials 0.000 title claims abstract description 97
- 239000003054 catalyst Substances 0.000 title claims abstract description 81
- 238000000746 purification Methods 0.000 title claims abstract description 28
- 239000000654 additive Substances 0.000 claims abstract description 93
- 230000000996 additive effect Effects 0.000 claims abstract description 93
- 239000011164 primary particle Substances 0.000 claims abstract description 72
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims abstract description 69
- 229910052751 metal Inorganic materials 0.000 claims abstract description 44
- 239000002184 metal Substances 0.000 claims abstract description 43
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 30
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000010948 rhodium Substances 0.000 claims abstract description 29
- 229910052703 rhodium Inorganic materials 0.000 claims abstract description 27
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000002245 particle Substances 0.000 claims abstract description 25
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 25
- 239000002344 surface layer Substances 0.000 claims abstract description 24
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 21
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 21
- 239000000203 mixture Substances 0.000 claims description 61
- 238000010304 firing Methods 0.000 claims description 35
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 23
- 229910001928 zirconium oxide Inorganic materials 0.000 claims description 23
- 229910052746 lanthanum Inorganic materials 0.000 claims description 15
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 15
- 239000002131 composite material Substances 0.000 claims description 13
- 229910052779 Neodymium Inorganic materials 0.000 claims description 12
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 12
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 10
- 229910052726 zirconium Inorganic materials 0.000 claims description 10
- 239000011575 calcium Substances 0.000 claims description 7
- 239000011777 magnesium Substances 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 6
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 6
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 6
- 229910052788 barium Inorganic materials 0.000 claims description 6
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 claims description 6
- 229910052791 calcium Inorganic materials 0.000 claims description 6
- 238000000975 co-precipitation Methods 0.000 claims description 6
- 229910052749 magnesium Inorganic materials 0.000 claims description 6
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 6
- 229910052727 yttrium Inorganic materials 0.000 claims description 6
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 6
- 229910052769 Ytterbium Inorganic materials 0.000 claims description 5
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 claims description 5
- 230000001590 oxidative effect Effects 0.000 claims description 4
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 3
- 229910052691 Erbium Inorganic materials 0.000 claims description 3
- 229910052693 Europium Inorganic materials 0.000 claims description 3
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 3
- 229910052689 Holmium Inorganic materials 0.000 claims description 3
- 229910052765 Lutetium Inorganic materials 0.000 claims description 3
- 229910052772 Samarium Inorganic materials 0.000 claims description 3
- 229910052771 Terbium Inorganic materials 0.000 claims description 3
- 229910052775 Thulium Inorganic materials 0.000 claims description 3
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims description 3
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 claims description 3
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 claims description 3
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 claims description 3
- KJZYNXUDTRRSPN-UHFFFAOYSA-N holmium atom Chemical compound [Ho] KJZYNXUDTRRSPN-UHFFFAOYSA-N 0.000 claims description 3
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 claims description 3
- 229910052712 strontium Inorganic materials 0.000 claims description 3
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 3
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 27
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 25
- 230000003197 catalytic effect Effects 0.000 description 13
- 239000011163 secondary particle Substances 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- 239000010410 layer Substances 0.000 description 9
- XNDZQQSKSQTQQD-UHFFFAOYSA-N 3-methylcyclohex-2-en-1-ol Chemical compound CC1=CC(O)CCC1 XNDZQQSKSQTQQD-UHFFFAOYSA-N 0.000 description 8
- 150000004683 dihydrates Chemical class 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- GJKFIJKSBFYMQK-UHFFFAOYSA-N lanthanum(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GJKFIJKSBFYMQK-UHFFFAOYSA-N 0.000 description 8
- 238000002360 preparation method Methods 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 229910017604 nitric acid Inorganic materials 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 230000004888 barrier function Effects 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910052738 indium Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 235000012501 ammonium carbonate Nutrition 0.000 description 2
- 239000001099 ammonium carbonate Substances 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- VQVDTKCSDUNYBO-UHFFFAOYSA-N neodymium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Nd+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VQVDTKCSDUNYBO-UHFFFAOYSA-N 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 239000010954 inorganic particle Substances 0.000 description 1
- 150000002500 ions Chemical group 0.000 description 1
- YXEUGTSPQFTXTR-UHFFFAOYSA-K lanthanum(3+);trihydroxide Chemical class [OH-].[OH-].[OH-].[La+3] YXEUGTSPQFTXTR-UHFFFAOYSA-K 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
- CFYGEIAZMVFFDE-UHFFFAOYSA-N neodymium(3+);trinitrate Chemical compound [Nd+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O CFYGEIAZMVFFDE-UHFFFAOYSA-N 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000013049 sediment Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000007962 solid dispersion Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
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- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- FRNOGLGSGLTDKL-UHFFFAOYSA-N thulium atom Chemical compound [Tm] FRNOGLGSGLTDKL-UHFFFAOYSA-N 0.000 description 1
- -1 ytterbim Chemical compound 0.000 description 1
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- Inorganic Compounds Of Heavy Metals (AREA)
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Abstract
Description
本発明は、無機酸化物、排気浄化用触媒担体及び排気浄化用触媒に関する。 The present invention relates to an inorganic oxide, an exhaust purification catalyst carrier, and an exhaust purification catalyst.
内燃機関等の排気の浄化に用いる排気浄化用触媒には、高温で長期間使用されても高い触媒活性を維持するために、極めて高い耐熱性を有することが求められる。 An exhaust gas purification catalyst used for purifying exhaust gas of an internal combustion engine or the like is required to have extremely high heat resistance in order to maintain high catalytic activity even when used at a high temperature for a long period of time.
排気浄化用触媒としては、例えば、粒子状の金属酸化物からなる担体に、触媒活性を有する金属を担持させたものが知られている。そして、このような排気浄化用触媒の耐熱性を高めるために、酸化ジルコニウム粒子に希土類元素の酸化物を均一に固溶したもの(特許文献1)や、酸化アルミニウムと希土類元素の酸化物とを組み合わせたもの(特許文献2)を担体として用いた触媒がこれまでに提案されている。
しかしながら、上記のような従来の触媒は、希土類元素を用いない場合と比較すれば高い耐熱性を有するものの、必ずしもまだ十分ではなかった。そこで、本発明者らは、耐熱性をさらに改善すべく詳細に検討したところ、従来の触媒においては、触媒活性を有する金属(以下、場合により「触媒金属」という。)を担持させる担体の耐熱性がまだ不足していることが明らかとなった。自動車の排気温度は通常600〜1000℃程度の高温に達するが、担体の耐熱性が不足すると、このような高温環境下において担体のシンタリングが進行し、これにより、担持された金属の粒成長が促進されると考えられる。金属の粒成長が促進されると、その比表面積が減少し、その結果、触媒活性が低下する。 However, the conventional catalyst as described above has high heat resistance as compared with the case where no rare earth element is used, but is not always sufficient. Therefore, the present inventors have studied in detail to further improve the heat resistance, and in the conventional catalyst, the heat resistance of the carrier supporting a metal having catalytic activity (hereinafter, sometimes referred to as “catalytic metal”). It became clear that sex was still lacking. The exhaust temperature of an automobile usually reaches a high temperature of about 600 to 1000 ° C. However, if the heat resistance of the carrier is insufficient, the sintering of the carrier proceeds under such a high temperature environment, thereby causing the growth of the supported metal grains. Will be promoted. When the metal grain growth is promoted, the specific surface area is reduced, and as a result, the catalytic activity is lowered.
本発明は、このような従来技術が有する問題点に鑑みてなされたものであり、担持された金属の粒成長が十分に抑制される無機酸化物、並びにこれからなる排気浄化用触媒担体及びこれを用いた排気浄化触媒を提供することを目的とする。 The present invention has been made in view of the above-described problems of the prior art, and includes an inorganic oxide in which grain growth of the supported metal is sufficiently suppressed, an exhaust purification catalyst carrier comprising the same, and a catalyst carrier for the same. An object of the present invention is to provide a used exhaust purification catalyst.
上記課題を解決するため、本発明は、酸化アルミニウムと、酸化アルミニウムとの複合酸化物を形成しない金属酸化物と、希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素と、を含有する粒子状の無機酸化物であって、酸化アルミニウムの含有割合が、酸化アルミニウム中のアルミニウム、上記金属酸化物中の金属元素及び添加元素の合計量に対して15〜40モル%であり、無機酸化物の一次粒子のうち80%以上が100nm以下の粒径を有し、一次粒子の少なくとも一部は、その表層部において添加元素の含有割合が局部的に高められた表面濃化領域を有することを特徴とするものである。 In order to solve the above problems, the present invention contains aluminum oxide, a metal oxide that does not form a composite oxide of aluminum oxide, and an additive element composed of at least one of a rare earth element and an alkaline earth element. It is a particulate inorganic oxide, and the content ratio of aluminum oxide is 15 to 40 mol% with respect to the total amount of aluminum in the aluminum oxide, the metal element in the metal oxide, and the additive element. 80% or more of the primary particles of the product have a particle size of 100 nm or less, and at least a part of the primary particles has a surface concentration region in which the content ratio of the additive element is locally increased in the surface layer portion. It is characterized by.
上記本発明の無機酸化物は、酸化アルミニウムとこれ以外の特定の金属酸化物とを特定の比率で組み合わせ、且つ、ナノメータスケールの大きさの一次粒子で主として構成され、さらに、希土類元素等の添加元素を、一次粒子の表層部において局部的に高濃度となるように含有することによって、高温環境下においても、担持された触媒金属の粒成長が十分に抑制される。 The inorganic oxide of the present invention is a combination of aluminum oxide and a specific metal oxide other than this in a specific ratio, and is mainly composed of primary particles having a nanometer scale size. By containing the element so as to have a locally high concentration in the surface layer portion of the primary particles, the grain growth of the supported catalyst metal is sufficiently suppressed even in a high temperature environment.
上記のような組み合わせで構成される無機酸化物においては、酸化アルミニウムと上記金属酸化物とは互いに複合酸化物を形成しないため、それぞれの酸化物を主成分として含有する一次粒子が別個に存在している。そして、これら異種の一次粒子が互いに介在しながら凝集して二次粒子を形成しているため、互いの粒子が拡散の障壁となって、一次粒子同士の融着によるシンタリングが抑制されると考えられる。また、酸化アルミニウムと他の金属酸化物を単に組み合わせた場合、高温の酸化性雰囲気下では、ロジウム等の触媒金属と固相反応してその触媒活性を低下させる場合があるが、酸化アルミニウムの含有割合を上記特定の範囲とすることによって、このような作用よりも、拡散障壁となることによる担体のシンタリング抑制のほうが支配的となって、触媒金属の粒成長抑制の効果が十分に得られることを本発明者らは見出した。 In the inorganic oxide composed of the combination as described above, aluminum oxide and the metal oxide do not form a composite oxide with each other, and therefore primary particles containing each oxide as a main component exist separately. ing. And since these different types of primary particles are aggregated while interposing each other to form secondary particles, the mutual particles serve as a diffusion barrier, and sintering due to fusion of the primary particles is suppressed. Conceivable. In addition, when aluminum oxide and other metal oxides are simply combined, in a high-temperature oxidizing atmosphere, the catalytic activity may decrease due to a solid-phase reaction with a catalytic metal such as rhodium. By setting the ratio within the above specific range, the suppression of the sintering of the support by becoming a diffusion barrier becomes more dominant than the above effect, and the effect of suppressing the grain growth of the catalyst metal can be sufficiently obtained. The present inventors have found that.
さらに、この無機粒子を構成する一次粒子の表層部において、添加元素の含有割合が局部的に高められた表面濃化領域が形成されている。言い換えると、添加元素の含有割合が高められた領域が、一次粒子の表面を覆うように形成されている。ただし、この領域は一次粒子の表面を完全に覆っている必要は必ずしもなく、一次粒子の表層部の少なくとも一部を覆っていればよい。上記のような添加元素は、酸化物となったときに塩基性を有するため、ロジウム(Rh)が担持されたときに、Rh−O−M(Mは担体中の添加元素)で表される結合を生成する。したがって、担体の一次粒子表面に希土類元素が多く存在すると、担持されたロジウム粒子が拡散しにくくなり、これによりロジウムの粒成長が効果的に抑制される。無機酸化物中の一次粒子は、表層部だけでなく、表面濃化領域よりも内層の部分(内層部分)においても添加元素を含有するが、希土類元素の含有割合を、局部的でなく、内層部分も含む一次粒子全体にわたって高くすると、ロジウム等の触媒金属との相互作用は強まる一方で、担体自体の耐熱性はかえって低下するために、触媒金属の粒成長が十分に抑制されなくなる。 Further, in the surface layer portion of the primary particles constituting the inorganic particles, a surface concentrated region in which the content ratio of the additive element is locally increased is formed. In other words, the region where the content of the additive element is increased is formed so as to cover the surface of the primary particles. However, this region does not necessarily need to completely cover the surface of the primary particles, and it is sufficient if it covers at least a part of the surface layer portion of the primary particles. Since the additive element as described above has basicity when it becomes an oxide, it is represented by Rh-OM (M is an additive element in the carrier) when rhodium (Rh) is supported. Create a bond. Accordingly, when a large amount of rare earth elements are present on the surface of the primary particles of the support, the supported rhodium particles are difficult to diffuse, and thereby the rhodium grain growth is effectively suppressed. The primary particles in the inorganic oxide contain the additive element not only in the surface layer portion but also in the inner layer portion (inner layer portion) rather than the surface concentrated region, but the content ratio of the rare earth element is not localized but the inner layer. When the height is increased over the entire primary particle including the portion, the interaction with the catalyst metal such as rhodium is strengthened, but the heat resistance of the support itself is lowered, so that the particle growth of the catalyst metal is not sufficiently suppressed.
また、本発明は、酸化アルミニウムと、酸化ジルコニウムと、希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素と、を含有する粒子状の無機酸化物であって、酸化アルミニウムの含有割合が、酸化アルミニウム中のアルミニウム、酸化ジルコニウム中のジルコニウム及び添加元素の合計量に対して15〜40モル%であり、無機酸化物の一次粒子のうち80%以上が100nm以下の粒径を有し、一次粒子の少なくとも一部は、その表層部において添加元素の含有割合が局部的に高められた表面濃化領域を有することを特徴とするものである。 Further, the present invention is a particulate inorganic oxide containing aluminum oxide, zirconium oxide, and an additive element consisting of at least one of a rare earth element and an alkaline earth element, and the content ratio of aluminum oxide is , 15 to 40 mol% based on the total amount of aluminum in aluminum oxide, zirconium in zirconium oxide and additive elements, and 80% or more of the primary particles of the inorganic oxide have a particle size of 100 nm or less, At least a part of the primary particles has a surface enriched region in which the content ratio of the additive element is locally increased in the surface layer portion.
酸化ジルコニウムは、酸化アルミニウムとの複合酸化物を実質的に形成しないため、これら酸化物を組み合わせた無機酸化物においては、酸化アルミニウム及び酸化ジルコニウムのそれぞれを主成分として含有する別個の一次粒子が形成される。したがって、この無機酸化物によっても、上述した無機酸化物と同様の効果が得られる。 Zirconium oxide does not substantially form a composite oxide with aluminum oxide, so in the inorganic oxides combining these oxides, separate primary particles containing each of aluminum oxide and zirconium oxide as the main components are formed. Is done. Therefore, the same effect as that of the above-described inorganic oxide can be obtained by this inorganic oxide.
表面濃化領域においては、酸化物の量に換算したときに、無機酸化物の全体量に対して1〜5質量%の添加元素が存在していることが好ましい。これにより、無機酸化物を触媒の担体として用いたときに、耐熱性に優れ、また、触媒活性もさらに高い触媒が得られる。 In the surface concentration region, it is preferable that 1 to 5% by mass of an additive element is present with respect to the total amount of the inorganic oxide when converted to the amount of the oxide. Thus, when an inorganic oxide is used as a catalyst carrier, a catalyst having excellent heat resistance and higher catalytic activity can be obtained.
本発明は、アルミニウム、酸化物となったときに酸化アルミニウムとの複合酸化物を形成しない金属元素、並びに、希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素、を含有する共沈物を得る共沈工程と、共沈物を焼成して酸化物の混合物を得る第一焼成工程と、混合物に希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素を付着し、これを更に焼成する第二焼成工程と、を備え、共沈物は、アルミニウム、上記金属元素及び添加元素が溶解した溶液から生成され、当該溶液におけるアルミニウムの含有割合が、その酸化物の量に換算したときに、アルミニウム、金属元素及び添加元素の合計量に対して15〜40モル%である製造方法によって得られることを特徴とする粒子状の無機酸化物である。 The present invention relates to a coprecipitate containing aluminum, a metal element that does not form a composite oxide with aluminum oxide when it becomes an oxide, and an additive element composed of at least one of a rare earth element and an alkaline earth element A co-precipitation step for obtaining a mixture, a first firing step for firing the co-precipitate to obtain a mixture of oxides, and adding an additive element comprising at least one of a rare earth element and an alkaline earth element to the mixture, A co-precipitate is generated from a solution in which aluminum, the metal element and the additive element are dissolved, and the aluminum content in the solution is converted to the amount of the oxide. And a particulate inorganic oxide obtained by a production method of 15 to 40 mol% with respect to the total amount of aluminum, metal element and additive element. That.
また、本発明は、アルミニウム、ジルコニウム、並びに、希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素、を含有する共沈物を得る共沈工程と、共沈物を焼成して酸化物の混合物を得る第一焼成工程と、混合物に希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素を付着し、これを更に焼成する第二焼成工程と、を備え、共沈物は、アルミニウム、ジルコニウム及び添加元素が溶解した溶液から生成され、当該溶液におけるアルミニウムの含有割合が、その酸化物の量に換算したときに、当該アルミニウム、ジルコニウム及び添加元素の合計量に対して15〜40モル%である製造方法によって得られることを特徴とする粒子状の無機酸化物である。 The present invention also provides a coprecipitation step for obtaining a coprecipitate containing aluminum, zirconium, and an additive element comprising at least one of a rare earth element and an alkaline earth element, and firing the coprecipitate to obtain an oxide. A first firing step for obtaining a mixture of the following, and a second firing step for adhering an additive element consisting of at least one of a rare earth element and an alkaline earth element to the mixture, and further firing the additional element. It is produced from a solution in which aluminum, zirconium and an additive element are dissolved, and the aluminum content in the solution is 15 to 40 with respect to the total amount of the aluminum, zirconium and additive element when converted to the amount of the oxide. It is a particulate inorganic oxide obtained by a production method of mol%.
このような特定の原料及び工程を組み合わせた製造方法によって得られる無機酸化物の一次粒子は、その中心部付近の内層部においては添加元素として上記共沈物に由来する部分を主として含有し、その表層部においては、添加元素として、第一焼成後の混合物に付着された部分を主として含有する。これにより、この一次粒子は、その表層部において添加元素の含有割合が局部的に高められた表面濃化領域を有する。また、この無機酸化物は、共沈物を得る溶液の組成を反映した、特定の比率で酸化アルミニウムを含有する。したがって、上記製造方法によって得られる無機酸化物は、すでに上述した無機酸化物とほぼ同様の構成を有するものであり、触媒の担体として用いたときに、高温環境下においても担持された触媒金属の粒成長が十分に抑制される。 The primary particles of the inorganic oxide obtained by the production method combining such specific raw materials and steps mainly contain a portion derived from the coprecipitate as an additive element in the inner layer portion in the vicinity of the central portion thereof. In the surface layer part, the part adhering to the mixture after the first firing is mainly contained as an additive element. Thereby, this primary particle has the surface concentration area | region where the content rate of the additive element was locally raised in the surface layer part. Moreover, this inorganic oxide contains aluminum oxide in a specific ratio reflecting the composition of the solution for obtaining the coprecipitate. Therefore, the inorganic oxide obtained by the above-described production method has a structure almost similar to that of the above-described inorganic oxide, and when used as a catalyst support, the supported catalyst metal is supported even in a high temperature environment. Grain growth is sufficiently suppressed.
上記第二焼成工程においては、酸化物の量に換算したときに、得られる無機酸化物の全体量に対して1〜5質量%となるような量の添加元素を付着することが、好ましい。これにより、触媒の担体として用いたときに、耐熱性に優れ、また、触媒活性もさらに高い触媒が得られる。 In said 2nd baking process, it is preferable to adhere | attach the quantity of an additional element which will be 1-5 mass% with respect to the whole quantity of the inorganic oxide obtained when converted into the quantity of an oxide. Thereby, when used as a catalyst carrier, a catalyst having excellent heat resistance and higher catalytic activity can be obtained.
また、第一焼成工程において、共沈物を酸化性雰囲気下で600〜1200℃に加熱して焼成し、第二焼成工程において、添加元素が付着した混合物を500〜900℃に加熱して焼成することが、好ましい。 In the first firing step, the coprecipitate is heated to 600 to 1200 ° C. in an oxidizing atmosphere and fired. In the second firing step, the mixture to which the additive element is attached is heated to 500 to 900 ° C. and fired. It is preferable to do.
以上のような本発明の無機酸化物が含有する添加元素として、希土類元素は、イットリウム、ランタン、プラセオジウム、ネオジウム(ネオジム)、サマリウム、ユウロピウム、ガドリニウム、テルビウム、ジスプロシウム、ホルミウム、エルビウム、ツリウム、イッテルビウム及びルテチウムからなる群より選ばれる少なくとも1種の元素であり、アルカリ土類元素は、マグネシウム、カルシウム、ストロンチウム及びバリウムからなる群より選ばれる少なくとも1種の元素であることが、好ましい。これらの中でも、添加元素としては、耐熱性の点から、イットリウム、ランタン、プラセオジム、ネオジウム、イッテルビム、マグネシウム、カルシム及びバリウムからなる少なくとも1種が好ましく、ランタン又はネオジウムが特に好ましい。 As an additive element contained in the inorganic oxide of the present invention as described above, rare earth elements include yttrium, lanthanum, praseodymium, neodymium (neodymium), samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and It is preferably at least one element selected from the group consisting of lutetium, and the alkaline earth element is preferably at least one element selected from the group consisting of magnesium, calcium, strontium and barium. Among these, the additive element is preferably at least one selected from yttrium, lanthanum, praseodymium, neodymium, ytterbim, magnesium, calcium and barium, and particularly preferably lanthanum or neodymium, from the viewpoint of heat resistance.
本発明の排気浄化用触媒担体は、上記本発明の無機酸化物を含んでなることを特徴とするものであり、本発明の排気浄化用触媒は、この排気浄化用触媒担体と、これに担持されたロジウムと、を備えることを特徴とするものである。さらに、触媒中のロジウムの少なくとも一部は、無機酸化物の一次粒子の表層部において添加元素の含有割合が局部的に高められた領域と接触するように担持されていることが、好ましい。この本発明の排気浄化用触媒は、上記本発明の無機酸化物を担体として用いていることによって、高温環境下においても、担持されたロジウムの粒成長が十分に抑制される。 The exhaust gas purification catalyst carrier of the present invention is characterized by comprising the inorganic oxide of the present invention, and the exhaust gas purification catalyst of the present invention comprises the exhaust gas purification catalyst carrier and a carrier carried thereon. Rhodium. Furthermore, it is preferable that at least a part of rhodium in the catalyst is supported so as to be in contact with a region where the content ratio of the additive element is locally increased in the surface layer portion of the primary particles of the inorganic oxide. The exhaust purification catalyst of the present invention uses the inorganic oxide of the present invention as a carrier, so that the grain growth of the supported rhodium is sufficiently suppressed even in a high temperature environment.
本発明によれば、担持された金属の粒成長が十分に抑制される無機酸化物、並びにこれからなる排気浄化用触媒担体及びこれを用いた排気浄化用触媒が提供される。 ADVANTAGE OF THE INVENTION According to this invention, the inorganic oxide by which the particle growth of the carry | supported metal is fully suppressed, the exhaust gas purification catalyst carrier which consists of this, and the exhaust gas purification catalyst using the same are provided.
以下に、本発明の好適な実施形態について詳細に説明する。ただし、本発明は以下の実施形態に限定されるものではない。 Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.
本発明の無機酸化物は、酸化アルミニウムと、酸化アルミニウムとの複合酸化物を形成しない金属酸化物と、希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素とを含有する粒子状の混合物からなるものである。 The inorganic oxide of the present invention is a particulate mixture containing aluminum oxide, a metal oxide that does not form a composite oxide of aluminum oxide, and an additive element comprising at least one of a rare earth element and an alkaline earth element It consists of
無機酸化物中の酸化アルミニウム(Al2O3)は、非晶質(例えば活性アルミナ)であっても、結晶質であってもよい。 Aluminum oxide (Al 2 O 3 ) in the inorganic oxide may be amorphous (for example, activated alumina) or crystalline.
無機酸化物における酸化アルミニウムの含有割合は、酸化アルミニウム中のアルミニウム、上記金属元素中の金属元素及び添加元素の合計量に対して15〜40モル%である。この割合が15モル%に満たないか、40モル%を超えると、触媒金属の粒成長が十分に抑制されなくなる。この割合は、触媒の耐熱性の点から、16〜35モル%であることがより好ましく、20〜30モル%であることがさらに好ましい。 The content ratio of aluminum oxide in the inorganic oxide is 15 to 40 mol% with respect to the total amount of aluminum in aluminum oxide, the metal element in the metal element, and the additive element. When this ratio is less than 15 mol% or exceeds 40 mol%, the grain growth of the catalyst metal is not sufficiently suppressed. This ratio is more preferably 16 to 35 mol%, and further preferably 20 to 30 mol%, from the viewpoint of heat resistance of the catalyst.
酸化アルミニウムとの複合酸化物を形成しない金属酸化物は、酸化アルミニウムとの組み合わせにおいて、互いに実質的に均一に固溶又は分散した状態の複合酸化物からなる一次粒子を形成しない酸化物である。言い換えると、この金属酸化物は、その前駆体としての水酸化物と水酸化アルミニウムとを共沈した共沈物を焼成したときに、酸化アルミニウムを主成分とする一次粒子とは別個に一次粒子を形成する。したがって、本発明の無機酸化物は、酸化アルミニウムを主成分として含有する第一の一次粒子と、酸化アルミニウム以外の金属酸化物を主成分として含有する第二の一次粒子とを含んでいる。 A metal oxide that does not form a composite oxide with aluminum oxide is an oxide that does not form primary particles composed of composite oxides in a state where they are substantially uniformly dissolved or dispersed in each other in combination with aluminum oxide. In other words, when the metal oxide is calcined with a coprecipitate obtained by coprecipitation of hydroxide as a precursor and aluminum hydroxide, the metal oxide is separated from primary particles mainly composed of aluminum oxide. Form. Therefore, the inorganic oxide of the present invention includes first primary particles containing aluminum oxide as a main component and second primary particles containing a metal oxide other than aluminum oxide as a main component.
これら一次粒子の少なくとも一部は、添加元素をさらに含有する。さらに、酸化アルミニウムを主成分とする一次粒子は、その表層部に少量の上記金属酸化物等を含有していてもよいし、上記金属元素を主成分とする一次粒子は、その表層部に少量の酸化アルミニウム等を含有していてもよい。 At least some of these primary particles further contain an additive element. Further, the primary particles mainly composed of aluminum oxide may contain a small amount of the metal oxide or the like in the surface layer portion, and the primary particles mainly composed of the metal element are small amounts in the surface layer portion. Aluminum oxide or the like may be contained.
そして、無機酸化物は、粒径100nm以下の複数の第一の一次粒子と、粒径100nm以下の複数の第二の一次粒子とで主として構成される二次粒子を含んでいる。これにより、組成の異なる一次粒子が互いに拡散の障壁となって、高温環境下における担体のシンタリングが抑制される。このように、組成の異なる一次粒子が別個に形成され、これら一次粒子が凝集して二次粒子が形成されていることは、後述する分析方法等によって確認することができる。 The inorganic oxide includes secondary particles mainly composed of a plurality of first primary particles having a particle size of 100 nm or less and a plurality of second primary particles having a particle size of 100 nm or less. As a result, primary particles having different compositions serve as diffusion barriers, and sintering of the carrier in a high temperature environment is suppressed. In this way, it is possible to confirm that primary particles having different compositions are formed separately, and that these primary particles are aggregated to form secondary particles by an analysis method described later.
無機酸化物中の一次粒子のうち粒子数の割合で80%以上は、比表面積を大きくして触媒活性を高めるために、100nm以下の粒径を有する。100nm以下の粒径を有する一次粒子の割合は、90%以上であることがより好ましく、95%以上であることがさらに好ましい。なお、この粒径は、1つの粒子に定義可能な直径のうちで最大のものとする。また、粒子状の無機酸化物全体における一次粒子の平均粒径は、1〜50nmであることが好ましく、3〜40nmであることがより好ましい。 80% or more of the primary particles in the inorganic oxide have a particle size of 100 nm or less in order to increase the specific surface area and increase the catalytic activity. The ratio of primary particles having a particle size of 100 nm or less is more preferably 90% or more, and further preferably 95% or more. This particle diameter is the largest diameter that can be defined for one particle. Moreover, the average particle diameter of the primary particles in the entire particulate inorganic oxide is preferably 1 to 50 nm, and more preferably 3 to 40 nm.
なお、一次粒子の粒径やそれぞれの組成、さらに二次粒子の凝集状態は、TEM(透過電子顕微鏡)、SEM(走査電子顕微鏡)、FE−STEM(フィールドエミッション−走査透過電子顕微鏡)、EDX(エネルギー分散型X線検出装置)、XPS(光電子分光分析装置)等を適宜組み合わせて無機酸化物を観察及び分析することにより、確認できる。 In addition, the primary particle size, each composition, and the aggregation state of the secondary particles are TEM (transmission electron microscope), SEM (scanning electron microscope), FE-STEM (field emission-scanning transmission electron microscope), EDX ( It can be confirmed by observing and analyzing the inorganic oxide by appropriately combining an energy dispersive X-ray detector), XPS (photoelectron spectrometer) and the like.
酸化アルミニウムと複合酸化物を形成しない金属酸化物としては、酸化ジルコニウム(ZrO2)、酸化ケイ素(SiO2)及び酸化チタン(TiO2)からなる群より選ばれる少なくとも1種を好適に用いることができる。これらの中でも、酸化ジルコニウムが特に好ましい。酸化ジルコニウムは、例えば触媒金属としてのロジウムと組み合わせたときに、耐熱性や触媒活性が特に優れた触媒が得られる。 As a metal oxide that does not form a composite oxide with aluminum oxide, it is preferable to use at least one selected from the group consisting of zirconium oxide (ZrO 2 ), silicon oxide (SiO 2 ), and titanium oxide (TiO 2 ). it can. Among these, zirconium oxide is particularly preferable. For example, when zirconium oxide is combined with rhodium as a catalyst metal, a catalyst having particularly excellent heat resistance and catalytic activity can be obtained.
希土類元素は、イットリウム(Y)、ランタン(La)、プラセオジウム(Pr)、ネオジウム(Nd)、サマリウム(Sm)、ユウロピウム(Eu)、ガドリニウム(Gd)、テルビウム(Tb)、ジスプロシウム(Dy)、ホルミウム(Ho)、エルビウム(Er)、ツリウム(Tm)、イッテルビウム(Yb)及びルテチウム(Lu)からなる群より選ばれる少なくとも1種の元素であることが好ましく、イットリウム、ランタン、プラセオジウム、ネオジウム及びイッテルビウムからなる群より選ばれる少なくとも1種の元素であることがより好ましい。一方、アルカリ土類元素は、マグネシウム(Mg)、カルシウム(Ca)、ストロンチウム(Sr)及びバリウム(Ba)からなる群より選ばれる少なくとも1種の元素であることが好ましく、マグネシウム、カルシウム及びバリウムからなる群より選ばれる少なくとも1種の元素であることがより好ましい。担体としての耐熱性等の点から、これらの中でも、希土類元素であるランタン又はネオジウムを添加元素として用いることが更に好ましい。この場合、ランタン及びネオジウムを併用してもよい。また、後述する表面濃化領域とこれ以外の領域とで、異なる添加元素を無機酸化物中に含有させてもよい。 Rare earth elements are yttrium (Y), lanthanum (La), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium It is preferably at least one element selected from the group consisting of (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu), from yttrium, lanthanum, praseodymium, neodymium and ytterbium. More preferably, it is at least one element selected from the group consisting of: On the other hand, the alkaline earth element is preferably at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba), and includes magnesium, calcium and barium. More preferably, it is at least one element selected from the group consisting of: Among these, lanthanum or neodymium, which is a rare earth element, is more preferably used as an additive element from the viewpoint of heat resistance as a support. In this case, lanthanum and neodymium may be used in combination. Further, different additive elements may be contained in the inorganic oxide in a surface enrichment region described later and other regions.
無機酸化物中の添加元素は、主としてその酸化物として、酸化アルミニウム又は上記金属酸化物に対して固溶、分散等した状態で存在している。特に、添加元素による本発明の効果をより顕著に発現させるため、無機酸化物の一次粒子の内層部分(表面濃化領域以外の部分)においては、添加元素の少なくとも一部が酸化アルミニウム又は上記金属酸化物に固溶していることが好ましい。この場合、酸化アルミニウム及び上記金属酸化物がともに添加元素を固溶していることがより好ましい。 The additive element in the inorganic oxide exists mainly as an oxide in a state of solid solution, dispersion, or the like with respect to aluminum oxide or the above metal oxide. In particular, in order to express the effect of the present invention by the additive element more remarkably, at least a part of the additive element is aluminum oxide or the above metal in the inner layer portion (the portion other than the surface concentrated region) of the primary particles of the inorganic oxide. It is preferably dissolved in the oxide. In this case, it is more preferable that the aluminum oxide and the metal oxide both have the additive element dissolved.
無機酸化物における添加元素の含有割合は、その酸化物の量に換算して、添加元素、酸化アルミニウム中のアルミニウム及び上記金属酸化物中の金属元素の合計量に対して1.5〜5.6モル%であることが好ましく、2.0〜4.0モル%であることがより好ましく、2.5〜3.8モル%であることがさらに好ましい。添加元素の酸化物の割合が1.5モル%未満である場合や、5.6モル%を超えた場合、高温環境下で触媒金属の粒成長が抑制されにくくなる傾向にある。また、添加元素が5.6モル%を超えると、触媒金属との相互作用が過剰に強くなって、触媒活性が低下する傾向にある。 The content ratio of the additive element in the inorganic oxide is 1.5 to 5.5 based on the total amount of the additive element, aluminum in the aluminum oxide, and the metal element in the metal oxide, in terms of the amount of the oxide. It is preferably 6 mol%, more preferably 2.0 to 4.0 mol%, and even more preferably 2.5 to 3.8 mol%. When the ratio of the oxide of the additive element is less than 1.5 mol% or exceeds 5.6 mol%, the particle growth of the catalyst metal tends to be hardly suppressed in a high temperature environment. On the other hand, when the additive element exceeds 5.6 mol%, the interaction with the catalyst metal becomes excessively strong, and the catalytic activity tends to decrease.
図1は、本発明の一実施形態に係る無機酸化物を、FE−STEMで観察したときの像を示す模式図である。図1の像における無機酸化物は、酸化アルミニウムとの複合酸化物を形成しない金属酸化物として酸化ジルコニウムを含有し、添加元素としてランタンを含有するものである。この像において、二次粒子24、25、26、27及び28はそれぞれ組成の異なる複数種の一次粒子が凝集して形成されている。一次粒子としては、主として酸化アルミニウムからなる一次粒子12と、主として酸化ジルコニウムからなる一次粒子14と、主として酸化アルミニウム及び酸化ランタンからなる一次粒子16と、主として酸化ジルコニウム及び酸化ランタンからなる一次粒子18とが存在している。酸化アルミニウムと酸化ジルコニウムとが互いに実質的に均一に固溶又は分散した複合酸化物からなる一次粒子は形成されていない。なお、各一次粒子における酸化物の組成や分布状態は、EDX等により分析することができる。
FIG. 1 is a schematic diagram showing an image when an inorganic oxide according to an embodiment of the present invention is observed by FE-STEM. The inorganic oxide in the image of FIG. 1 contains zirconium oxide as a metal oxide that does not form a composite oxide with aluminum oxide, and contains lanthanum as an additive element. In this image, the
二次粒子22、25、27及び28は一次粒子12、14、16及び18が、それぞれ凝集して形成されている。また、一次粒子14及び18からなる二次粒子24や、一次粒子12及び16からなる二次粒子26のような二次粒子が一部存在していてもよい。二次粒子24及び26が存在する場合、これら二次粒子にまれる金属元素は、無機酸化物中に存在する全金属元素に対して30モル%以下であることが好ましく、15モル%以下であることがより好ましく、10モル%以下であることが更に好ましい。
The
上記無機酸化物を構成する一次粒子の少なくとも一部は、その表層部において、添加元素の含有割合が局部的に高められた表面濃化領域を有している。無機酸化物を構成する一次粒子のうち酸化ランタンを含有するものについては、実質的に全てがこの表面濃化領域を有していることが好ましいが、本発明の効果を著しく損なわない程度に、表面濃化領域を有しない一次粒子が混在していてもよい。なお、酸化ランタンを主たる構成成分としない一次粒子についても、その表層部において、添加元素が存在していてもよい。 At least a part of the primary particles constituting the inorganic oxide has a surface concentration region in which the content ratio of the additive element is locally increased in the surface layer portion. Of the primary particles constituting the inorganic oxide, those containing lanthanum oxide preferably have substantially all of this surface enriched region, but to the extent that the effects of the present invention are not significantly impaired. Primary particles that do not have a surface concentrated region may be mixed. Note that an additive element may also be present in the surface layer of primary particles that do not contain lanthanum oxide as a main constituent.
表面濃化領域における添加元素は、一次粒子の表層部に存在している。表面濃化領域に存在している添加元素の量は、無機酸化物の全体量に対して1〜5質量%であることが好ましい。この量が1質量%に満たないか又は5質量%を超えると、添加元素による触媒の耐熱性向上の効果が減少する傾向にある。 The additive element in the surface concentration region exists in the surface layer portion of the primary particles. The amount of the additive element present in the surface concentration region is preferably 1 to 5% by mass with respect to the total amount of the inorganic oxide. If this amount is less than 1% by mass or exceeds 5% by mass, the effect of improving the heat resistance of the catalyst by the additive element tends to decrease.
表面濃化領域に存在している添加元素は、硝酸水溶液等の酸性溶液と接触したときに溶出する。したがって、表面濃化領域に存在している添加元素の量は、無機酸化物を硝酸水溶液に接触させたときに、硝酸水溶液中に溶出する添加元素の量を定量することによって、確認できる。より具体的には、例えば、無機酸化物0.1gを10mlの1N硝酸水溶液に加え、これを2時間攪拌して表面濃化領域に存在している添加元素を溶出し、溶出した添加元素の量を化学分析により定量することにより、存在している添加元素の量を確認できる。 The additive elements present in the surface concentration region are eluted when they come into contact with an acidic solution such as an aqueous nitric acid solution. Therefore, the amount of the additive element present in the surface concentration region can be confirmed by quantifying the amount of the additive element eluted in the nitric acid aqueous solution when the inorganic oxide is brought into contact with the nitric acid aqueous solution. More specifically, for example, 0.1 g of inorganic oxide is added to 10 ml of 1N nitric acid aqueous solution, and this is stirred for 2 hours to elute the additive elements present in the surface concentration region. By quantifying the amount by chemical analysis, the amount of additive elements present can be confirmed.
このような表面濃化領域を有する一次粒子を含む無機酸化物は、例えば、添加元素の酸化物を含む複数種の酸化物からなる混合物の粒子に添加元素を付着し、これを更に焼成することによって得ることができる。この方法によって得られる無機酸化物の一次粒子においては、付着された添加元素の大部分は、焼成により酸化物となるとともに、一次粒子表層部に存在して、表面濃化領域を形成する。 The inorganic oxide containing primary particles having such a surface-enriched region may be obtained by, for example, attaching the additive element to particles of a mixture composed of a plurality of types of oxides including the oxide of the additive element, and further firing it. Can be obtained by: In the primary particles of the inorganic oxide obtained by this method, most of the adhering additive elements are converted into oxides by firing, and are present in the primary particle surface layer portion to form a surface concentrated region.
上記の方法により表面濃化領域を有する一次粒子を含む無機酸化物を得る場合、酸化物の混合物に付着する添加元素の量は、その酸化物の質量に換算したときに、得られる無機酸化物の全体量に対して1〜5質量%とすることが好ましい。これにより、得られる無機酸化物を、その一次粒子の表層部においてほぼ1〜5質量%の添加元素が存在しているものとすることができる。 When an inorganic oxide containing primary particles having a surface-enriched region is obtained by the above method, the amount of the additive element adhering to the oxide mixture is obtained when converted to the mass of the oxide. It is preferable to set it as 1-5 mass% with respect to the whole quantity. Thereby, about 1-5 mass% of additional elements can exist in the surface layer part of the primary particle of the obtained inorganic oxide.
無機酸化物の一次粒子において、上記のような表面濃化領域が形成されていることは、上述のような添加元素の溶出による方法の他、例えば、EDX(エネルギー分散型X線検出装置)、SIMS(二次イオン質量分析装置)等を用いて組成分析して、一次粒子表層部と中心部とで添加元素の含有割合を比較することにより確認できる。あるいは、一次粒子中心部について直接組成分析するのに代えて、無機酸化物についてICP(高周波プラズマ発光分析装置)等の方法で組成分析して無機酸化物全体の平均値としての添加元素の含有割合を定量し、表層部での添加元素の含有割合がこれよりも高いことを確認してもよい。 In the primary particles of the inorganic oxide, the surface enrichment region as described above is formed in addition to the method by elution of the additive element as described above, for example, EDX (energy dispersive X-ray detector), This can be confirmed by analyzing the composition using a SIMS (secondary ion mass spectrometer) or the like and comparing the content ratio of the additive element between the primary particle surface layer part and the central part. Alternatively, instead of directly analyzing the composition of the central part of the primary particles, the composition ratio of the inorganic oxide is analyzed by a method such as ICP (high frequency plasma emission spectrometer), and the content ratio of the additive element as the average value of the entire inorganic oxide May be determined, and it may be confirmed that the content ratio of the additive element in the surface layer portion is higher than this.
以上説明したような無機酸化物は、例えば、アルミニウム、酸化物となったときに酸化アルミニウムとの複合酸化物を形成しない金属元素、並びに、希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素、を含有する共沈物を得る共沈工程と、この共沈物を焼成して酸化物の混合物を得る第一焼成工程と、この混合物に希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素を付着し、これを更に焼成する第二焼成工程と、を備える製造方法によって好適に得ることができる。 The inorganic oxide as described above includes, for example, aluminum, a metal element that does not form a composite oxide with aluminum oxide when it becomes an oxide, and an addition of at least one of a rare earth element and an alkaline earth element A coprecipitation step of obtaining a coprecipitate containing the element, a first firing step of firing the coprecipitate to obtain a mixture of oxides, and the mixture from at least one of a rare earth element and an alkaline earth element It can be suitably obtained by a manufacturing method comprising: a second baking step in which an additional element to be attached is attached and further fired.
上記共沈物は、アルミニウム、上記金属元素及び添加元素が溶解した溶液から生成される。この溶液におけるアルミニウムの含有割合は、その酸化物(Al2O3)の量に換算したときに、アルミニウム、上記金属元素及び添加元素の合計量に対して15〜40モル%である。これにより、得られる無機酸化物における酸化アルミニウムの含有割合を、ほぼ15〜40モル%とすることができる。この含有割合は、16〜35モル%であることがより好ましく、20〜30モル%であることがより好ましい。 The coprecipitate is generated from a solution in which aluminum, the metal element, and the additive element are dissolved. The aluminum content in this solution is 15 to 40 mol% with respect to the total amount of aluminum, the metal element and the additive element when converted to the amount of the oxide (Al 2 O 3 ). Thereby, the content rate of the aluminum oxide in the obtained inorganic oxide can be made into about 15-40 mol%. The content is more preferably 16 to 35 mol%, and more preferably 20 to 30 mol%.
また、上記溶液における添加元素の含有割合は、その酸化物の量に換算したときに、当該添加元素、アルミニウム及び上記金属元素の合計量に対して、0.2〜4.0モル%とすることが好ましく、0.5〜3.8モル%とすることがより好ましい。溶液中の添加元素が0.2モル%に満たないか又は4.0モル%を超えると、得られる無機酸化物を担体として用いたときに、触媒金属の粒成長を抑制する効果が低下する傾向にある。 Further, the content ratio of the additive element in the solution is 0.2 to 4.0 mol% with respect to the total amount of the additive element, aluminum, and the metal element when converted to the amount of the oxide. It is preferably 0.5 to 3.8 mol%. When the additive element in the solution is less than 0.2 mol% or exceeds 4.0 mol%, the effect of suppressing the grain growth of the catalyst metal is lowered when the obtained inorganic oxide is used as a support. There is a tendency.
上記溶液としては、無機酸化物を構成する各金属元素の塩等を水、アルコール等に溶解したものが好適に用いられる。この塩としては、硫酸塩、硝酸塩、塩酸塩、酢酸塩などが挙げられる。 As said solution, what melt | dissolved the salt of each metal element which comprises an inorganic oxide, etc. in water, alcohol, etc. is used suitably. Examples of the salt include sulfate, nitrate, hydrochloride, acetate, and the like.
この溶液をアルカリ性溶液と混合するなどして、溶液のpHを各金属元素の水酸化物が析出するような範囲(好ましくはpH9以上)となるように調整することにより、アルミニウム等を含有する共沈物が生成する。アルカリ性溶液としては、アンモニア、炭酸アンモニウム等の溶液を用いることができる。これらの中でも、焼成時等において揮発により除去しやすい点等から、アンモニア又は炭酸アンモニウムの溶液が好ましい。 This solution is mixed with an alkaline solution so that the pH of the solution is adjusted to a range in which the hydroxide of each metal element is precipitated (preferably pH 9 or more). A sediment is formed. As the alkaline solution, a solution of ammonia, ammonium carbonate or the like can be used. Among these, an ammonia or ammonium carbonate solution is preferable because it can be easily removed by volatilization during firing.
続く第一焼成工程において、得られた共沈物を、好ましくは遠心分離及び洗浄した後、加熱により焼成して、酸化物の混合物を得る。この第一焼成工程では、大気雰囲気等の酸化性雰囲気下、600〜1200℃で好ましくは0.5〜10時間加熱して共沈物を焼成するのがよい。 In the subsequent first firing step, the obtained coprecipitate is preferably centrifuged and washed, and then fired by heating to obtain a mixture of oxides. In the first firing step, the coprecipitate is fired by heating at 600 to 1200 ° C., preferably for 0.5 to 10 hours, in an oxidizing atmosphere such as an air atmosphere.
さらに、第二焼成工程において、酸化物の混合物に添加元素を付着し、これを更に焼成することにより、粒子状の無機酸化物が得られる。付着は、添加元素の塩(硝酸塩等)が溶解した溶液中に、酸化物の混合物を懸濁させてこれを攪拌するなどにより行うことができる。また、この第二焼成工程では、添加元素が付着した混合物を、500〜900℃で、好ましくは酸性雰囲気下0.5〜10時間加熱して焼成するのがよい。 Furthermore, in the second firing step, an additive element is attached to the oxide mixture, and further fired to obtain a particulate inorganic oxide. The adhesion can be performed by suspending a mixture of oxides in a solution in which a salt of an additive element (nitrate or the like) is dissolved and stirring the mixture. Moreover, in this 2nd baking process, it is good to heat and bake the mixture to which the additional element adhered at 500-900 degreeC, Preferably it is 0.5 to 10 hours in an acidic atmosphere.
本発明の排気浄化用触媒担体は、以上説明した無機酸化物を少なくとも含んでなる担体である。この担体に、例えば、ロジウム、白金及びパラジウムからなる群より選ばれる1種以上の貴金属を触媒金属として好適に担持させることができる。 The exhaust purification catalyst carrier of the present invention is a carrier comprising at least the inorganic oxide described above. For example, one or more kinds of noble metals selected from the group consisting of rhodium, platinum and palladium can be suitably supported on the carrier as a catalyst metal.
本発明の排気浄化用触媒は、上記本発明の排気浄化用触媒担体と、これに担持されたロジウムと、を備えることを特徴とするものである。この触媒は、上記本発明の無機酸化物を担体として用いていることによって、高温環境下においても、担持されたロジウムの粒成長が十分に抑制される。ロジウムは、含浸法等の従来公知の方法を採用して、担体に担持させることができる。 The exhaust purification catalyst of the present invention comprises the exhaust purification catalyst carrier of the present invention and rhodium supported on the catalyst support. By using the inorganic oxide of the present invention as a carrier, this catalyst can sufficiently suppress the grain growth of the supported rhodium even in a high temperature environment. Rhodium can be supported on a carrier by employing a conventionally known method such as an impregnation method.
本発明の排気浄化用触媒中のロジウムの少なくとも一部は、無機酸化物の一次粒子の表層部において添加元素の含有割合が局部的に高められた領域(表面濃化領域)と接触するように担持されていることが、好ましい。これにより、添加元素によるロジウムの粒成長抑制の効果がより顕著に発現する。 At least a portion of rhodium in the exhaust purification catalyst of the present invention is in contact with a region (surface enriched region) in which the content of the additive element is locally increased in the surface layer portion of the primary particles of the inorganic oxide. It is preferably supported. Thereby, the effect of suppressing the grain growth of rhodium by the additive element is more remarkably exhibited.
ロジウムを担持させる量は、十分に高い触媒活性を発現させるため、担体質量に対して0.01〜3質量%であることが好ましく、0.05〜2質量%であることがより好ましく、0.1〜1質量%であることが更に好ましい。 The amount of rhodium supported is preferably 0.01 to 3% by mass, more preferably 0.05 to 2% by mass with respect to the mass of the carrier in order to develop sufficiently high catalytic activity. More preferably, it is 1-1 mass%.
排気浄化用触媒を使用する形態は特に限定されず、例えば、ハニカム形状のモノリス基材、ペレット基材又はフォーム基材などの基材の表面上に排気浄化用触媒からなる層を形成させて、これを内燃機関等の排気流路中に配置する等して用いることができる。 The form using the exhaust purification catalyst is not particularly limited, for example, by forming a layer made of the exhaust purification catalyst on the surface of a substrate such as a honeycomb-shaped monolith substrate, pellet substrate or foam substrate, This can be used by arranging it in an exhaust passage of an internal combustion engine or the like.
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.
(実施例1)
<触媒の調製>
0.43モルの硝酸アルミニウム9水和物、0.95モルのオキシ硝酸ジルコニル2水和物及び0.05モルの硝酸ランタン6水和物を1600mlのイオン交換水に溶解して得た溶液を、十分に攪拌しながら、溶液中の金属カチオンに対する中和当量の1.2倍のアンモニアを含有するアンモニア水に加えて溶液のpHを9以上とし、アルミニウム、ジルコニウム及びランタンの水酸化物を共沈させてこれらを含有する共沈物を生成させた。そして、共沈物を遠心分離してから十分に洗浄した後、大気中400℃で5時間加熱して仮焼成した。続いて、仮焼成後の固形物を、大気中700℃で5時間加熱してから、さらに900℃で5時間加熱することにより焼成(第一焼成)して、酸化アルミニウム、酸化ジルコニウム及び酸化ランタンを含有する酸化物の混合物を得た。混合物の組成比は酸化アルミニウム/酸化ジルコニウム/酸化ランタン=21.5/95/2.5(モル比)であり、混合物における酸化アルミニウムの含有割合は、アルミニウム、ジルコニウム及びランタンの合計量に対して15モル%であった。
Example 1
<Preparation of catalyst>
A solution obtained by dissolving 0.43 mol of aluminum nitrate nonahydrate, 0.95 mol of zirconyl oxynitrate dihydrate and 0.05 mol of lanthanum nitrate hexahydrate in 1600 ml of ion-exchanged water was used. With sufficient stirring, the pH of the solution is adjusted to 9 or more in addition to ammonia water containing 1.2 times the neutralization equivalent of the metal cations in the solution, and aluminum, zirconium and lanthanum hydroxides are co- A coprecipitate containing these was produced by precipitation. Then, the coprecipitate was centrifuged and sufficiently washed, and then heated at 400 ° C. in the atmosphere for 5 hours to be pre-baked. Subsequently, the pre-baked solid material is heated in the atmosphere at 700 ° C. for 5 hours, and further heated at 900 ° C. for 5 hours to be fired (first baking), thereby producing aluminum oxide, zirconium oxide, and lanthanum oxide. A mixture of oxides containing was obtained. The composition ratio of the mixture is aluminum oxide / zirconium oxide / lanthanum oxide = 21.5 / 95 / 2.5 (molar ratio), and the content ratio of aluminum oxide in the mixture is based on the total amount of aluminum, zirconium and lanthanum. It was 15 mol%.
得られた混合物47.5gを、6.5gの硝酸ランタン6水和物(酸化ランタン(La2O3)の量に換算すると、得られる無機酸化物の全体量に対して5質量%となる量)が溶解した硝酸ランタン水溶液中で懸濁させた懸濁液を、2時間攪拌した。その後、懸濁液から水を蒸発させて残った固形物を、大気中110℃で12時間加熱した後、更に大気中800℃で5時間加熱することにより焼成(第二焼成)し、粒子状の無機酸化物を得た。この無機酸化物中の一次粒子は、複合酸化物を形成後さらに後添加元素としてランタンを加えたことによって、表層部において添加元素としてのランタンの含有割合が局部的に高められている。また、得られた無機酸化物をTEMにより観察したところ、一次粒子の80%以上が100nm以下の粒径を有していることが確認された。 When 47.5 g of the obtained mixture is converted into an amount of 6.5 g of lanthanum nitrate hexahydrate (lanthanum oxide (La 2 O 3 )), it becomes 5% by mass with respect to the total amount of the obtained inorganic oxide. The suspension suspended in the aqueous lanthanum nitrate solution in which the amount was dissolved was stirred for 2 hours. Then, after the water was evaporated from the suspension, the solid matter remaining was heated in the atmosphere at 110 ° C. for 12 hours and then further heated in the atmosphere at 800 ° C. for 5 hours to be fired (second firing) to form particles. An inorganic oxide was obtained. The primary particles in the inorganic oxide are locally increased in content of lanthanum as an additive element in the surface layer portion by adding lanthanum as a post-addition element after forming the composite oxide. Moreover, when the obtained inorganic oxide was observed by TEM, it was confirmed that 80% or more of the primary particles have a particle size of 100 nm or less.
得られた無機酸化物を担体として、これをRh(NO3)3水溶液中に加えて攪拌した後、水を蒸発させて残った固形物を大気中500℃で3時間加熱して焼成したものを、長さ0.5〜1mmのペレット状に成形して、担体にロジウムが担持された触媒を得た。担持されたロジウムの量は担体100gに対して約0.5gであった。 Using the obtained inorganic oxide as a carrier, this was added to a Rh (NO 3 ) 3 aqueous solution and stirred, and then the water was evaporated and the remaining solid was baked by heating at 500 ° C. in the atmosphere for 3 hours. Was shaped into a pellet having a length of 0.5 to 1 mm to obtain a catalyst having rhodium supported on a carrier. The amount of rhodium supported was about 0.5 g with respect to 100 g of the carrier.
<触媒の耐久性(耐熱性)試験>
得られたペレット状の触媒を、耐久試験装置内に配置して触媒層を形成させ、ガスの触媒層入口温度を1000℃、空間速度を10000/時間に設定して、表1に示す組成のリッチガス及びリーンガスを5分間ずつ交互に触媒層に流通させる耐久試験を5時間行った。耐久試験後の触媒について、CO吸着法によりロジウム分散性(全ロジウム原子中、粒子表面に露出するロジウム原子の割合)を測定した。ロジウム分散性の数値が大きいことは、大きな比表面積を維持していることに対応し、ロジウム粒子の粒成長が抑制されていることを意味する。
<Durability (heat resistance) test of catalyst>
The obtained pellet-shaped catalyst was placed in an endurance test apparatus to form a catalyst layer, the gas catalyst layer inlet temperature was set to 1000 ° C., and the space velocity was set to 10,000 / hour, and the composition shown in Table 1 was obtained. An endurance test in which rich gas and lean gas were alternately passed through the catalyst layer for 5 minutes was performed for 5 hours. With respect to the catalyst after the durability test, rhodium dispersibility (ratio of rhodium atoms exposed on the particle surface in all rhodium atoms) was measured by a CO adsorption method. A large value of rhodium dispersibility corresponds to maintaining a large specific surface area and means that grain growth of rhodium particles is suppressed.
(実施例2)
1モルの硝酸アルミニウム9水和物、0.95モルのオキシ硝酸ジルコニル2水和物及び0.05モルの硝酸ランタン6水和物を1600mlのイオン交換水に溶解して得た溶液を用いて共沈物を生成させ、第一焼成後の混合物の組成を酸化アルミニウム/酸化ジルコニウム/酸化ランタン=50/95/2.5とし、混合物における酸化アルミニウムの含有割合を25モル%とした他は、実施例1と同様にして、無機酸化物及び触媒の調製と、触媒の耐久性試験とを行った。
(Example 2)
Using a solution obtained by dissolving 1 mol of aluminum nitrate nonahydrate, 0.95 mol of zirconyl oxynitrate dihydrate and 0.05 mol of lanthanum nitrate hexahydrate in 1600 ml of ion-exchanged water Except that a coprecipitate was produced, the composition of the mixture after the first firing was aluminum oxide / zirconium oxide / lanthanum oxide = 50/95 / 2.5, and the aluminum oxide content in the mixture was 25 mol%, In the same manner as in Example 1, preparation of the inorganic oxide and catalyst and durability test of the catalyst were performed.
(実施例3)
1.5モルの硝酸アルミニウム9水和物、0.95モルのオキシ硝酸ジルコニル2水和物及び0.05モルの硝酸ランタン6水和物を1600mlのイオン交換水に溶解して得た溶液を用いて共沈物を生成させ、第一焼成後の混合物の組成を酸化アルミニウム/酸化ジルコニウム/酸化ランタン=75/95/2.5とし、混合物における酸化アルミニウムの含有割合を30モル%とした他は、実施例1と同様にして、無機酸化物及び触媒の調製と、触媒の耐久性試験とを行った。
Example 3
A solution obtained by dissolving 1.5 mol of aluminum nitrate nonahydrate, 0.95 mol of zirconyl oxynitrate dihydrate and 0.05 mol of lanthanum nitrate hexahydrate in 1600 ml of ion-exchanged water was used. The coprecipitate was produced using the mixture, the composition of the mixture after the first firing was aluminum oxide / zirconium oxide / lanthanum oxide = 75/95 / 2.5, and the aluminum oxide content in the mixture was 30 mol%. In the same manner as in Example 1, preparation of inorganic oxide and catalyst and durability test of the catalyst were performed.
(実施例4)
2.0モルの硝酸アルミニウム9水和物、0.95モルのオキシ硝酸ジルコニル2水和物及び0.05モルの硝酸ランタン6水和物を1600mlのイオン交換水に溶解して得た溶液を用いて共沈物を生成させ、第一焼成後の混合物の組成を酸化アルミニウム/酸化ジルコニウム/酸化ランタン=100/95/2.5とし、混合物における酸化アルミニウムの含有割合を33.3モル%とした他は、実施例1と同様にして、無機酸化物及び触媒の調製と、触媒の耐久性試験とを行った。
Example 4
A solution obtained by dissolving 2.0 mol of aluminum nitrate nonahydrate, 0.95 mol of zirconyl oxynitrate dihydrate and 0.05 mol of lanthanum nitrate hexahydrate in 1600 ml of ion-exchanged water was used. The co-precipitate is produced, the composition of the mixture after the first firing is aluminum oxide / zirconium oxide / lanthanum oxide = 100/95 / 2.5, and the aluminum oxide content in the mixture is 33.3 mol%. In the same manner as in Example 1, the preparation of the inorganic oxide and the catalyst and the durability test of the catalyst were performed.
(実施例5)
4.0モルの硝酸アルミニウム9水和物、0.95モルのオキシ硝酸ジルコニル2水和物及び0.05モルの硝酸ランタン6水和物を1600mlのイオン交換水に溶解して得た溶液を用いて共沈物を生成させ、第一焼成後の混合物の組成を酸化アルミニウム/酸化ジルコニウム/酸化ランタン=200/95/2.5とし、混合物における酸化アルミニウムの含有割合を40モル%とした他は、実施例1と同様にして、無機酸化物及び触媒の調製と、触媒の耐久性試験とを行った。
(Example 5)
A solution obtained by dissolving 4.0 mol of aluminum nitrate nonahydrate, 0.95 mol of zirconyl oxynitrate dihydrate and 0.05 mol of lanthanum nitrate hexahydrate in 1600 ml of ion-exchanged water was used. In addition to producing a coprecipitate, the composition of the mixture after the first firing was aluminum oxide / zirconium oxide / lanthanum oxide = 200/95 / 2.5, and the aluminum oxide content in the mixture was 40 mol%. In the same manner as in Example 1, preparation of inorganic oxide and catalyst and durability test of the catalyst were performed.
(実施例6)
第一焼成後の混合物を、硝酸ジルコニウム水溶液に代えて、6.6gの硝酸ネオジウム6水和物が溶解した硝酸ネオジウム水溶液中で懸濁させた他は、実施例2と同様にして、無機酸化物及び触媒の調製と、触媒の耐久性試験とを行った。
(Example 6)
Inorganic oxidation was performed in the same manner as in Example 2 except that the mixture after the first baking was suspended in an aqueous solution of neodymium nitrate in which 6.6 g of neodymium nitrate hexahydrate was dissolved instead of the aqueous solution of zirconium nitrate. The product and catalyst were prepared, and the durability test of the catalyst was performed.
(実施例7)
1モルの硝酸アルミニウム9水和物、0.95モルのオキシ硝酸ジルコニル2水和物及び0.05モルの硝酸ネオジウム6水和物を1600mlのイオン交換水に溶解して得た溶液を用いて共沈物を生成させ、第一焼成後の混合物の組成を酸化アルミニウム/酸化ジルコニウム/酸化ネオジウム=50/95/2.5とし、混合物における酸化アルミニウムの含有割合を25モル%とした他は、実施例1と同様にして、無機酸化物及び触媒の調製と、触媒の耐久性試験とを行った。
(Example 7)
Using a solution obtained by dissolving 1 mol of aluminum nitrate nonahydrate, 0.95 mol of zirconyl oxynitrate dihydrate and 0.05 mol of neodymium nitrate hexahydrate in 1600 ml of ion-exchanged water Except that a coprecipitate was produced, the composition of the mixture after the first firing was aluminum oxide / zirconium oxide / neodium oxide = 50/95 / 2.5, and the aluminum oxide content in the mixture was 25 mol%, In the same manner as in Example 1, preparation of the inorganic oxide and catalyst and durability test of the catalyst were performed.
(比較例1)
0.25モルの硝酸アルミニウム9水和物、0.95モルのオキシ硝酸ジルコニル2水和物及び0.05モルの硝酸ランタン6水和物を1600mlのイオン交換水に溶解して得た溶液を用いて共沈物を生成させ、第一焼成後の混合物の組成を酸化アルミニウム/酸化ジルコニウム/酸化ランタン=12.5/95/2.5とし、混合物における酸化アルミニウムの含有割合を10モル%とした他は、実施例1と同様にして、無機酸化物及び触媒の調製と、触媒の耐久性試験とを行った。
(Comparative Example 1)
A solution obtained by dissolving 0.25 mol of aluminum nitrate nonahydrate, 0.95 mol of zirconyl oxynitrate dihydrate and 0.05 mol of lanthanum nitrate hexahydrate in 1600 ml of ion-exchanged water was used. To produce a coprecipitate, the composition of the mixture after the first firing is aluminum oxide / zirconium oxide / lanthanum oxide = 12.5 / 95 / 2.5, and the aluminum oxide content in the mixture is 10 mol% In the same manner as in Example 1, the preparation of the inorganic oxide and the catalyst and the durability test of the catalyst were performed.
(比較例2)
6モルの硝酸アルミニウム9水和物、0.95モルのオキシ硝酸ジルコニル2水和物及び0.05モルの硝酸ランタン6水和物を1600mlのイオン交換水に溶解して得た溶液を用いて共沈物を生成させ、第一焼成後の混合物の組成を酸化アルミニウム/酸化ジルコニウム/酸化ランタン=300/95/2.5とし、混合物における酸化アルミニウムの含有割合を42.9モル%とした他は、実施例1と同様にして、無機酸化物及び触媒の調製と、触媒の耐久性試験とを行った。
(Comparative Example 2)
Using a solution obtained by dissolving 6 mol of aluminum nitrate nonahydrate, 0.95 mol of zirconyl oxynitrate dihydrate and 0.05 mol of lanthanum nitrate hexahydrate in 1600 ml of ion-exchanged water A coprecipitate was produced, the composition of the mixture after the first firing was aluminum oxide / zirconium oxide / lanthanum oxide = 300/95 / 2.5, and the aluminum oxide content in the mixture was 42.9 mol%. In the same manner as in Example 1, preparation of inorganic oxide and catalyst and durability test of the catalyst were performed.
表2に示すように、酸化アルミニウムを15〜40モル%の範囲内で含有する混合物にランタン又はネオジウムをさらに付着させて得た実施例1〜7の触媒によれば、高温環境下での耐久性試験後のロジウム分散性は十分に大きい値を示した。これに対して、酸化アルミニウムの含有割合が上記範囲内にない比較例1及び2については、耐久性試験後のロジウム分散性は低いものであった。したがって、本発明によれば、担持された触媒金属の粒成長が十分に抑制される無機酸化物、並びにこれを用いた排気浄化用触媒が得られることが確認された。 As shown in Table 2, according to the catalysts of Examples 1 to 7 obtained by further attaching lanthanum or neodymium to a mixture containing aluminum oxide in the range of 15 to 40 mol%, durability in a high temperature environment The rhodium dispersibility after the property test showed a sufficiently large value. On the other hand, the rhodium dispersibility after the durability test was low for Comparative Examples 1 and 2 in which the aluminum oxide content was not within the above range. Therefore, according to the present invention, it was confirmed that an inorganic oxide in which grain growth of the supported catalyst metal is sufficiently suppressed and an exhaust purification catalyst using the inorganic oxide can be obtained.
12、14、16、18…一次粒子、22、24、25、26、27、28…二次粒子。 12, 14, 16, 18 ... primary particles, 22, 24, 25, 26, 27, 28 ... secondary particles.
Claims (13)
前記酸化アルミニウムの含有割合が、前記酸化アルミニウム中のアルミニウム、前記金属酸化物中の金属元素及び前記添加元素の合計量に対して15〜40モル%であり、
前記無機酸化物の一次粒子のうち80%以上が100nm以下の粒径を有し、
前記一次粒子の少なくとも一部は、その表層部において前記添加元素の含有割合が局部的に高められた表面濃化領域を有する、無機酸化物。 A particulate inorganic oxide containing aluminum oxide, a metal oxide that does not form a composite oxide of aluminum oxide, and an additive element composed of at least one of a rare earth element and an alkaline earth element,
The content ratio of the aluminum oxide is 15 to 40 mol% with respect to the total amount of aluminum in the aluminum oxide, the metal element in the metal oxide, and the additive element,
80% or more of the primary particles of the inorganic oxide have a particle size of 100 nm or less,
At least a part of the primary particles is an inorganic oxide having a surface concentrated region in which the content of the additive element is locally increased in the surface layer portion.
前記酸化アルミニウムの含有割合が、前記酸化アルミニウム中のアルミニウム、前記酸化ジルコニウム中のジルコニウム及び前記添加元素の合計量に対して15〜40モル%であり、
前記無機酸化物の一次粒子のうち80%以上が100nm以下の粒径を有し、
前記一次粒子の少なくとも一部は、その表層部において前記添加元素の含有割合が局部的に高められた表面濃化領域を有する、無機酸化物。 A particulate inorganic oxide containing aluminum oxide, zirconium oxide, and an additive element composed of at least one of a rare earth element and an alkaline earth element,
The content ratio of the aluminum oxide is 15 to 40 mol% with respect to the total amount of aluminum in the aluminum oxide, zirconium in the zirconium oxide and the additive element,
80% or more of the primary particles of the inorganic oxide have a particle size of 100 nm or less,
At least a part of the primary particles is an inorganic oxide having a surface concentrated region in which the content of the additive element is locally increased in the surface layer portion.
前記共沈物を焼成して酸化物の混合物を得る第一焼成工程と、
前記混合物に希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素を付着し、これを更に焼成する第二焼成工程と、を備え、
前記共沈物は、前記アルミニウム、前記金属元素及び前記添加元素が溶解した溶液から生成され、
当該溶液における前記アルミニウムの含有割合が、その酸化物の量に換算したときに、当該アルミニウム、前記金属元素及び前記添加元素の合計量に対して15〜40モル%である製造方法によって得られる粒子状の無機酸化物。 Coprecipitation to obtain a coprecipitate containing aluminum, a metal element that does not form a complex oxide with aluminum oxide when it becomes an oxide, and an additive element consisting of at least one of a rare earth element and an alkaline earth element Process,
A first firing step of firing the coprecipitate to obtain a mixture of oxides;
A second firing step of attaching an additive element composed of at least one of a rare earth element and an alkaline earth element to the mixture, and further firing the additive element,
The coprecipitate is generated from a solution in which the aluminum, the metal element, and the additive element are dissolved,
Particles obtained by a production method in which the content ratio of the aluminum in the solution is 15 to 40 mol% with respect to the total amount of the aluminum, the metal element, and the additive element when converted to the amount of the oxide -Like inorganic oxide.
前記共沈物を焼成して酸化物の混合物を得る第一焼成工程と、
前記混合物に希土類元素及びアルカリ土類元素のうち少なくとも一方からなる添加元素を付着し、これを更に焼成する第二焼成工程と、を備え、
前記共沈物は、前記アルミニウム、前記ジルコニウム及び前記添加元素が溶解した溶液から生成され、
当該溶液における前記アルミニウムの含有割合が、その酸化物の量に換算したときに、当該アルミニウム、前記ジルコニウム及び前記添加元素の合計量に対して15〜40モル%である製造方法によって得られる粒子状の無機酸化物。 A coprecipitation step of obtaining a coprecipitate containing aluminum, zirconium, and an additive element comprising at least one of a rare earth element and an alkaline earth element;
A first firing step of firing the coprecipitate to obtain a mixture of oxides;
A second firing step of attaching an additive element composed of at least one of a rare earth element and an alkaline earth element to the mixture, and further firing the additive element,
The coprecipitate is generated from a solution in which the aluminum, the zirconium, and the additive element are dissolved,
When the content ratio of the aluminum in the solution is converted to the amount of the oxide, it is in the form of particles obtained by a production method that is 15 to 40 mol% with respect to the total amount of the aluminum, the zirconium, and the additive element. Inorganic oxide.
前記第二焼成工程において、前記添加元素が付着した前記混合物を500〜900℃に加熱して焼成する、請求項4〜6の何れか一項に記載の無機酸化物。 In the first firing step, the coprecipitate is heated to 600 to 1200 ° C. in an oxidizing atmosphere and fired,
The inorganic oxide according to any one of claims 4 to 6, wherein in the second firing step, the mixture to which the additive element is attached is heated to 500 to 900 ° C and fired.
前記アルカリ土類元素は、マグネシウム、カルシウム、ストロンチウム及びバリウムからなる群より選ばれる少なくとも1種の元素である、請求項1〜7の何れか一項に記載の無機酸化物。 The rare earth element is at least one element selected from the group consisting of yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium,
The inorganic oxide according to any one of claims 1 to 7, wherein the alkaline earth element is at least one element selected from the group consisting of magnesium, calcium, strontium, and barium.
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