JP2004306000A - Base material for carrying catalyst and its producing method - Google Patents
Base material for carrying catalyst and its producing method Download PDFInfo
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- JP2004306000A JP2004306000A JP2003126130A JP2003126130A JP2004306000A JP 2004306000 A JP2004306000 A JP 2004306000A JP 2003126130 A JP2003126130 A JP 2003126130A JP 2003126130 A JP2003126130 A JP 2003126130A JP 2004306000 A JP2004306000 A JP 2004306000A
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- catalyst
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- 239000003054 catalyst Substances 0.000 title claims abstract description 120
- 239000000463 material Substances 0.000 title claims abstract description 26
- 238000000034 method Methods 0.000 title abstract description 7
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 47
- 239000010936 titanium Substances 0.000 claims abstract description 47
- DUFCMRCMPHIFTR-UHFFFAOYSA-N 5-(dimethylsulfamoyl)-2-methylfuran-3-carboxylic acid Chemical compound CN(C)S(=O)(=O)C1=CC(C(O)=O)=C(C)O1 DUFCMRCMPHIFTR-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims abstract description 23
- 150000001342 alkaline earth metals Chemical class 0.000 claims abstract description 19
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 238000002441 X-ray diffraction Methods 0.000 claims abstract description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000001354 calcination Methods 0.000 claims abstract description 9
- 239000001301 oxygen Substances 0.000 claims abstract description 9
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 9
- 150000003608 titanium Chemical class 0.000 claims abstract description 9
- 239000000758 substrate Substances 0.000 claims description 92
- 229910000510 noble metal Inorganic materials 0.000 claims description 83
- 239000002131 composite material Substances 0.000 claims description 26
- 238000010304 firing Methods 0.000 claims description 25
- 239000010948 rhodium Substances 0.000 claims description 15
- 238000004519 manufacturing process Methods 0.000 claims description 14
- -1 alkaline earth metal salt Chemical class 0.000 claims description 5
- 238000005470 impregnation Methods 0.000 claims description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 5
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 4
- 229910052763 palladium Inorganic materials 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- 229910052703 rhodium Inorganic materials 0.000 claims description 3
- VBIXEXWLHSRNKB-UHFFFAOYSA-N ammonium oxalate Chemical group [NH4+].[NH4+].[O-]C(=O)C([O-])=O VBIXEXWLHSRNKB-UHFFFAOYSA-N 0.000 claims description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 2
- 230000003197 catalytic effect Effects 0.000 abstract description 12
- 230000006866 deterioration Effects 0.000 abstract description 11
- 239000004480 active ingredient Substances 0.000 abstract description 3
- 239000004615 ingredient Substances 0.000 abstract 2
- 239000000843 powder Substances 0.000 description 100
- 125000004429 atom Chemical group 0.000 description 81
- 239000000243 solution Substances 0.000 description 52
- 239000007789 gas Substances 0.000 description 49
- 229910052719 titanium Inorganic materials 0.000 description 29
- 229910052726 zirconium Inorganic materials 0.000 description 27
- 230000000052 comparative effect Effects 0.000 description 24
- 239000007858 starting material Substances 0.000 description 23
- 238000005245 sintering Methods 0.000 description 22
- 239000002585 base Substances 0.000 description 20
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 18
- CDQFODAJQFUTJR-UHFFFAOYSA-M [NH4+].[O-]C(=O)C(=O)O[Ti] Chemical compound [NH4+].[O-]C(=O)C(=O)O[Ti] CDQFODAJQFUTJR-UHFFFAOYSA-M 0.000 description 16
- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 16
- 230000000694 effects Effects 0.000 description 11
- 239000006104 solid solution Substances 0.000 description 9
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 8
- 230000007423 decrease Effects 0.000 description 8
- 150000003839 salts Chemical class 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 7
- 238000011156 evaluation Methods 0.000 description 7
- 239000011777 magnesium Substances 0.000 description 7
- UEGPKNKPLBYCNK-UHFFFAOYSA-L magnesium acetate Chemical compound [Mg+2].CC([O-])=O.CC([O-])=O UEGPKNKPLBYCNK-UHFFFAOYSA-L 0.000 description 6
- 229940069446 magnesium acetate Drugs 0.000 description 6
- 235000011285 magnesium acetate Nutrition 0.000 description 6
- 239000011654 magnesium acetate Substances 0.000 description 6
- 229910010413 TiO 2 Inorganic materials 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 5
- 238000000746 purification Methods 0.000 description 5
- 239000000446 fuel Substances 0.000 description 4
- 229910052749 magnesium Inorganic materials 0.000 description 4
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 4
- 239000012071 phase Substances 0.000 description 4
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- 229910003023 Mg-Al Inorganic materials 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 125000004430 oxygen atom Chemical group O* 0.000 description 2
- 239000002574 poison Substances 0.000 description 2
- 231100000614 poison Toxicity 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 238000002407 reforming Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 229910052809 inorganic oxide Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- NWAHZABTSDUXMJ-UHFFFAOYSA-N platinum(2+);dinitrate Chemical compound [Pt+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O NWAHZABTSDUXMJ-UHFFFAOYSA-N 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000011973 solid acid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- HDUMBHAAKGUHAR-UHFFFAOYSA-J titanium(4+);disulfate Chemical compound [Ti+4].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O HDUMBHAAKGUHAR-UHFFFAOYSA-J 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、触媒活性成分を担持するのに用いられる基材に係り、更に詳細には、耐熱性に優れ、耐久後においても、貴金属のシンタリングや固溶が抑制され、貴金属の良好な分散性が維持される触媒担持用基材、その製造方法及びこの基材を用いた触媒に関する。
【０００２】
【従来の技術】
従来、貴金属の熱劣化（シンタリング、基材への固溶等）を抑制するために種々の提案がされている。例えば、ロジウム（Ｒｈ）を高分散させる方法として、担持基材であるアルミナに一旦固溶させ、還元処理する方法が提案されている（例えば、特許文献１参照。）。
また、高耐熱性触媒担持用基材として、アルカリ金属元素・アルカリ土類金属元素、アルミナ、チタニア、ジルコニア、シリカ等を含有した非晶質の複合酸化物を用いることが提案されている（例えば、特許文献２参照。）。
【０００３】
【特許文献１】
特開平９−２９９７９６号公報
【特許文献２】
特開平９−１２２４８６号公報
【０００４】
【発明が解決しようとする課題】
しかしながら、特許文献１に記載されているような方法では、触媒が再び高温で酸素雰囲気に曝されると、Ｒｈがアルミナ基材に固溶してしまう可能性があり、未だ十分とは言えなかった。
また、特許文献２に記載されている高耐熱性触媒担持用基材にあっても、貴金属の熱劣化抑制性能が十分とは言い難い。
【０００５】
本発明は、このような従来技術の有する課題に鑑みてなされたものであり、その目的とするところは、触媒活性成分の熱劣化を抑制し、触媒性能を向上し、使用する触媒活性成分の量を低減し得る触媒担持用基材、その製造方法及び該基材を用いた触媒を提供することにある。
【０００６】
【課題を解決するための手段】
本発明者らは、上記目的を達成すべく鋭意検討を重ねた結果、チタンとジルコニア等を含有する特定の耐熱性無機複合酸化物を形成することなどにより、上記目的が達成できることを見出し、本発明を完成するに至った。
【０００７】
即ち、本発明の触媒担持用基材は、次式▲１▼
［Ｔｉ］ａ［Ｚｒ］ｂ［Ａｌ］ｃＯｘ…▲１▼
（式中のａは０．０１≦ａ≦０．２、ｂは０．０１≦ｂ≦０．２、ｃはｃ＝２−ａ−ｂの関係を満足し、ｘは化学量論を満たす酸素数を示す。）で表される組成を有する耐熱性無機複合酸化物を含有するものであって、触媒活性成分を担持した後の耐久後に所定の（上記表Ａで特定される）Ｘ線回折パターン（２θ−ｄ値）を示す。
【０００８】
また、本発明の他の触媒担持用基材は、次式▲２▼
［Ｔｉ］ａ［Ｚｒ］ｂ［α］ｃ［Ａｌ］ｄＯｘ…▲２▼
（式中のａは０．０１≦ａ≦０．２、ｂは０．０１≦ｂ≦０．２、ｃは０．０１≦ｃ≦０．２、ｄはｄ＝２−ａ−ｂ−ｃの関係を満足し、ｘは化学量論を満たす酸素数、αはアルカリ土類金属元素を示す。）で表される組成を有する耐熱性無機複合酸化物を含有するものであって、触媒活性成分を担持した後の耐久後に所定の（上記表Ｂで特定される）Ｘ線回折パターンを示す。
【０００９】
更に、本発明の触媒担持用基材の製造方法は、上述した触媒用担持基材を製造する方法である。
触媒担持用基材の別に応じて、水溶性チタン塩と酢酸ジルコニウムをアルミナに含浸した後に焼成するか、水溶性チタン塩と酢酸ジルコニウムとアルカリ土類金属塩をアルミナに含浸した後に焼成する。
【００１０】
更にまた、本発明の触媒は、本発明の触媒担持用基材の少なくとも一方を用いたものであり、一方の触媒担持用基材又は双方の触媒担持用基材の混合物に、触媒活性成分、特に貴金属を担持して成る。
【００１１】
【発明の実施の形態】
以下、本発明の触媒担持用基材について詳細に説明する。なお、本明細書において、「％」は特記しない限り、質量百分率を表すものとする。
【００１２】
上述の如く、本発明の触媒担持用基材は、触媒活性成分、代表的には貴金属を担持するのに用いられる基材であって、アルカリ土類金属を含むものと含まないものとの２種類がある。
ここで、アルカリ土類金属を含まない担持用基材は、次の▲１▼式
［Ｔｉ］ａ［Ｚｒ］ｂ［Ａｌ］ｃＯｘ…▲１▼
（式中のａは０．０１≦ａ≦０．２、ｂは０．０１≦ｂ≦０．２、ｃはｃ＝２−ａ−ｂの関係を満足し、ｘは化学量論を満たす酸素数を示す。）で表される組成を有する耐熱性無機複合酸化物を含有する。
また、触媒活性成分を担持した後の耐久後、代表的には、空気気流中９００〜１０００℃で１〜３時間放置した後、次の表Ａで表されるＸ線回折パターンを示す。
【００１３】
【表３】
▲１▼式において、Ｔｉ又はＺｒのＡｌに対する原子比はａ又はｂで示すように０．０１〜０．２であるが、この原子比が０．２を超えると、ＴｉやＺｒがチタニア（ＴｉＯ２）やジルコニア（ＺｒＯ２）として単独の酸化物を形成してしまい複合酸化物が得られず、比表面積の低下を招き、アルミナ表面の改質が不可能になる。
一方、この原子比が０．０１未満では十分なアルミナ改質効果が得られず、触媒活性成分である貴金属の熱劣化抑制に寄与することができない。
【００１５】
また、Ｔｉ又はＺｒのＡｌに対する原子比はａを０．０２≦ａ≦０．０９、ｂを０．０１≦ｂ≦０．０７とすることがより好ましい。これは、一般的にＴｉＯ２−ＺｒＯ２は等分子量混合時に最も酸強度が高くなることが知られており、このためＴｉＯ２とＺｒＯ２を等分子量付近で混合させたときにアルミナ表面の水酸基との結合性が最も強く、アルミナと複合酸化物を作り易いためと考えられる。
ＴｉのＡｌに対する原子比が０．０１≦ａ≦０．０２の範囲ではアルミナの改質効果は得られているが、例えば触媒活性成分がＲｈである場合には、この範囲ではＲｈ固溶の起点となり得る入口状サイトが残存していると考えられる。また０．０９≦ａ≦０．２の範囲では、Ｔｉ原子による十分な表面改質効果は得られているが、若干のＴｉＯ２が単独の酸化物としてアルミナ上に形成し始めるために、より効果的にアルミナ表面の改質を行うためにはＴｉ原子比を０．０２≦ａ≦０．０９とすることが望ましい。
【００１６】
ＺｒのＡｌに対する原子比についても同様の理由から０．０１≦ｂ≦０．０７とすることがより好ましい。但し、分子径はＴｉＯ２＜ＺｒＯ２であり、比較的分子径の大きなＺｒＯ２はＴｉＯ２に対して効果的にアルミナ表面の改質を行うことのできる範囲が狭く、比較的ＺｒＯ２がアルミナ表面に析出し易くなり、触媒活性成分がアルミナ細孔に吸着しづらくなるため触媒活性が低下し易いと考えられる。
なお、▲１▼式において、酸素原子比ｘは通常２である。
【００１７】
この触媒担持用基材は、▲１▼式で表される複合酸化物を主成分とするが、この基材全体が該複合酸化物のみから構成されている必要はなく、例えば、完全な複合酸化物を形成していないチタニア、ジルコニア及びアルミナ（Ａｌ２Ｏ３）などの混合物を部分的に有していてもよい。但し、基材全体としては、均質で一体的に把握され得るものであり、この意味では基材組成物と言い得る。
また、基材全体として上記表Ａに示すＸ線回折パターンを示すが、このパターンは、本発明外の複合酸化物や基材と比較すると、相対強度比に特異性が認められる（後述する実施例や比較例を参照。）。この相対強度比の特異性は、アルミナの熱劣化抑制効果と合致し、本発明の触媒担持用基材においては、上記のような耐久後であっても、アルミナのγ−アルミナからθ−アルミナへの相転移が進行し難くなっている。
【００１８】
一般に、触媒担持用基材の熱劣化は、通常は主成分であるアルミナのγ−アルミナ→θ−アルミナ→α−アルミナという一連の相転移による焼結に起因する。よって、本発明の担持用基材によれば、例えば、担持する触媒活性成分がＰｔやＰｄの場合には、基材を焼結する際に生じる比表面積の低下に伴うシンタリングを抑制することができ、Ｒｈの場合は、アルミナへの固溶を抑制できる。
この作用の詳細は現時点では不明だが、以下のように推測できる。
即ち、何も添加していないアルミナにＲｈを担持して高温で焼成すると、Ｒｈがアルミナへ固溶してしまう。この現象はＲｈの固溶という問題点として一般に知られているが、かかるＲｈの固溶は、担持基材が相転移する際に、Ｒｈがアルミナのバルク（内部）に取り込まれ、この結果、触媒表面（基材表面）に露出できるＲｈ量が減少したものと考えられている。
これに対し、本発明の担持用基材では、Ｔｉ原子とＺｒ原子がアルミナ表面に共存してアルミナ表面を改質しており、例えば、基材の固体酸性質の増大に伴う貴金属の酸化状態を改善したり、Ｒｈ固溶の起点となり得る入口状サイトが基材表面（アルミナ表面）に生成するのを抑制しているものと推測できる。
【００１９】
次に、本発明の触媒担持用基材のうちアルカリ土類金属元素を含むものは、次式▲２▼
［Ｔｉ］ａ［Ｚｒ］ｂ［α］ｃ［Ａｌ］ｄＯｘ…▲２▼
（式中のａは０．０１≦ａ≦０．２、ｂは０．０１≦ｂ≦０．２、ｃは０．０１≦ｃ≦０．２、ｄはｄ＝２−ａ−ｂ−ｃの関係を満足し、ｘは化学量論を満たす酸素数、αはアルカリ土類金属元素を示す。）で表される組成を有する耐熱性無機複合酸化物を含有し、上記耐久後のＸ線回折パターンが、次の表Ｂで表される。
【００２０】
【表４】
▲２▼式において、Ｔｉ及びＺｒの原子比についての限定理由は、▲１▼式の場合と同様で、Ｔｉ又はＺｒのＡｌに対する原子比はａを０．０１≦ａ≦０．０９、ｂを０．０１≦ｂ≦０．０６とすることがより好ましく。また、この複合酸化物全体が完全な化合物となっていなくてもよい点も同様であるが、この複合酸化物において、酸素原子比ｘは通常４である。
また、▲２▼式から明らかなように、この複合酸化物は、更にアルカリ土類金属元素を含有する。このように、アルカリ土類金属元素を含有させることにより、アルミナの耐熱性をいっそう向上させることができる。しかし、単にアルカリ土類金属元素を基材に含ませると、貴金属に酸素を与えやすくなり、貴金属の触媒性能に悪影響を及ぼす可能性がある。この点、本発明では、ＴｉやＺｒで基材表面を上述の如く改質しているので、アルカリ土類金属を含有させることにより、基材の耐熱性を有効に向上させることができ、従って、貴金属の触媒性能を更に向上させることができる。
なお、本発明においては、アルカリ土類金属元素であれば単独で又は任意に組み合わせて用いることができるが、特にマグネシウムを好適に用いることができる。
【００２２】
また、このアルカリ土類金属元素を含有する触媒担持用基材は、上述のように、耐久後に表Ｂで表されるＸ線回折パターンを示し、結晶子径が異なる。
かかる結晶子径の相違は、この担持用基材の方が基材粉末の焼結がいっそう抑制されていることを示しており、耐熱性がいっそう良好であることを示している。
【００２３】
次に、本発明の触媒担持用基材の製造方法について説明する。
上述の如く、本発明の製造方法は、得ようとする▲１▼式又は▲２▼式の複合酸化物の別に応じて、▲１▼式の複合酸化物では水溶性チタン塩と酢酸ジルコニウム、▲２▼式の複合酸化物では更にアルカリ土類金属塩を用い、これらを水相でアルミナに含有させ、乾燥した後、焼成する方法である。
ここで、水溶性のＴｉ塩を用いるのは、非水溶性のＴｉ塩であるチタンイソプロポキシドなどを用いると、ルチル型のチタニアの結晶が成長してしまい、アルミナ表面の改質を十分に行えなくなって貴金属の分散度が低下すると考えられるからである。また一般に、高比表面無機酸化物基材であるアルミナは、その表面に多数の水酸基を有し水系溶媒となじみ易いので、Ｔｉによってアルミナ表面の改質を十分に行うには、このようなアルミナ表面との親和性が高く、この表面にチタンを高分散可能とする、水溶性のＴｉ塩を用いることが望ましいからである。
【００２４】
なお、上記水溶性Ｔｉ塩としては、有機カルボン酸アンモニウム塩を用いることが望ましい。
他の水溶性塩である硫酸塩や塩化物を用いると、硫黄分や塩素分が焼成後においても触媒中に残留し、これらが触媒毒として貴金属を失活させてしまう可能性がある。これに対し、シュウ酸アンモニウム塩を用いると、これらは全て焼成後に二酸化炭素と水に酸化分解されるので、触媒毒となり得る元素が触媒中に残留せず、▲１▼式又は▲２▼式の組成や所定のＸ線回折パターンを有する複合酸化物の性能を十分に活用することができ、貴金属の触媒活性が低下するのを有効に抑制できる。
【００２５】
また、ジルコニウム成分の含浸に関しても、上記同様の理由から酢酸ジルコニウムを使用するが、上述のような不具合を回避できれば、特に限定されるものではない。
更に、アルカリ土類金属塩としても、上記チタン塩の場合と同様の選択理由から、これらの酢酸塩、炭酸塩、硝酸塩、水酸化物等を好適に使用できるが、特に限定されるものではない。
【００２６】
なお、アルミナとしては、高比表面積を有すれば特に限定されるものではないが、アルミナの相転移に起因する熱劣化の悪影響を有効に防止するには、γ−アルミナを用いることが好ましい。
かかる熱劣化によりアルミナの表面積が低下するので、担持された貴金属の触媒性能の低下を抑制するためには、アルミナの表面積低下、即ち担持用基材の表面積低下を抑制すべく、高比表面積のγ−アルミナを使用することが望ましいからである。
【００２７】
含浸法については、ＴｉとＺｒをアルミナに担持できれば特に限定されるものではないが、これらを共含浸することが望ましい。
共含浸によれば、各成分の担持比率を制御し易く、また、工程数を少なくできるため作業効率が向上し、更に、成分の担持毎に焼成する場合に生じると推測される触媒担持用基材の劣化が少ないと考えられる。
【００２８】
なお、アルカリ土類金属を担持させる場合には、Ｔｉ及びＺｒの一方又は双方と、該アルカリ土類金属とを担持し、次いで、Ｔｉ及びＺｒの一方又は双方を担持することができ、Ｚｒと該アルカリ土類金属とを担持し、次いで、Ｔｉを担持することができる。
【００２９】
焼成処理については、上述した所望の複合酸化物が得られる限り特に限定されるものではないが、代表的には、空気気流中９００〜１０００℃で１〜３時間、好ましくは９００〜９５０℃で２〜３時間加熱することにより焼成を行うことである。
焼成温度が９００℃未満では、請求項に示す構造が得られず、１０００℃より高いと比表面積の低いα−アルミナが生じてしまう可能性がある。
また、１時間未満では、請求項に示す構造が得られず、３時間より長く焼成しても、所望の複合酸化物を得られるものの経済的ではない。
【００３０】
なお、本発明の製造方法においては、上記焼成処理前に乾燥を行い、得られた乾燥粉末を粉砕し、その後に焼成処理に供してもよく、これにより、基材粉末の均一性を向上できる。
【００３１】
次に、本発明の触媒について説明する。
本発明の触媒は、上述した本発明の触媒担持用基材を用いたものであり、▲１▼式及び表Ａ、▲２▼式及び表Ｂで特定される担持用基材を少なくとも１種用い、当該基材に貴金属などの触媒活性成分を担持したものである。
本発明の触媒は、上述の如くその担持用基材が熱安定性に優れるという利点から、貴金属の劣化抑制に優れた効果を示し、触媒が酸化雰囲気に曝される環境下において特に有効である。
なお、用途としては、特に限定されるものではないが、本発明の触媒担持用基材の優れた熱安定性による貴金属の劣化抑制効果により、高温且つ酸化雰囲気に長時間にわたり曝される図１に示すような自動車等の排気ガス浄化触媒として用いることで特に優れた効果を発揮することができる。また、同様に酸化雰囲気に曝される環境下として図２に示すような燃料電池における空気極側の電極触媒や図３に示すような燃料電池から排出される還元ガスの浄化触媒として使用することができる。
【００３２】
また、触媒活性成分の例である貴金属としては、Ｐｔ、Ｒｈ又はＰｄ及びこれらの任意の混合物を例示することができ、本発明の触媒は、特にＲｈの固溶に対する改善効果が顕著である。
なお、本発明の触媒は、そのままでも使用可能であり、また粒状やペレット状に成形して使用することも可能であるが、一体構造型担体に担持して用いることも可能である。
かかる一体構造型担体としては、コーディエライトなどのセラミックスやフェライト系ステンレスなどの金属等の耐熱性材料から成るモノリス担体やハニカム担体を例示できる。
【００３３】
【実施例】
以下、本発明を実施例及び比較例により更に詳細に説明する。
【００３４】
［触媒担持用基材］
（実施例１）
酸化アルミニウム粉末中に含まれる２原子分のＡｌに対して、０．０１原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．１９原子分のＺｒ原子を含む酢酸ジルコニウム溶液とを、酸化アルミニウム粉末に含浸し、次いで、空気気流中１５０℃で２０時間乾燥した後、一旦粉砕し、しかる後、空気気流中９００℃で３時間焼成し、本例の触媒担持用基材（実施粉末１）を得た。
【００３５】
（実施例２）
０．０３原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０３原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例１と同様の操作を繰り返し、本例の触媒担持用基材（実施粉末２）を得た。
【００３６】
（実施例３）
０．１９原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０５原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例１と同様の操作を繰り返し、本例の触媒担持用基材（実施粉末３）を得た。
【００３７】
（実施例４）
０．１５原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０１原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例１と同様の操作を繰り返し、本例の触媒担持用基材（実施粉末４）を得た。
【００３８】
（実施例５）
０．１原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．１原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用い、粉末焼成温度を９５０℃とした以外は、実施例１と同様の操作を繰り返し、本例の担持用基材（実施粉末５）を得た。
【００３９】
（実施例６）
粉末焼成温度を１０００℃、焼成時間を４時間とした以外は実施例１と同様の操作を繰り返し、本例の担持用基材（実施粉末６）を得た。
【００４０】
（実施例７）
粉末焼成温度を１０００℃、焼成時間を４時間とした以外は実施例２と同様の操作を繰り返し、本例の担持用基材（実施粉末７）を得た。
【００４１】
（実施例８）
粉末焼成温度を１０００℃、焼成時間を４時間とした以外は実施例３と同様の操作を繰り返し、本例の担持用基材（実施粉末８）を得た。
【００４２】
（実施例９）
粉末焼成温度を１０００℃、焼成時間を４時間とした以外は実施例４と同様の操作を繰り返し、本例の担持用基材（実施粉末９）を得た。
【００４３】
（実施例１０）
０．０３原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０２原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用い、粉末焼成温度を９００℃、焼成時間を２．５時間とした以外は、実施例１と同様の操作を繰り返し、本例の担持用基材（実施粉末１０）を得た。
【００４４】
（実施例１１）
０．０２原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０７原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例１０と同様の操作を繰り返し、本例の担持用基材（実施粉末１１）を得た。
【００４５】
（実施例１２）
０．０９原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０１原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例１０と同様の操作を繰り返し、本例の担持用基材（実施粉末１２）を得た。
【００４６】
（実施例１３）
焼成温度を９５０℃、焼成時間を３時間とした以外は実施例１０と同様の操作を繰り返し、本例の担持用基材（実施粉末１３）を得た。
【００４７】
（実施例１４）
焼成温度を９５０℃、焼成時間を３時間とした以外は実施例１１と同様の操作を繰り返し、本例の担持用基材（実施粉末１４）を得た。
【００４８】
（実施例１５）
焼成温度を９５０℃、焼成時間を３時間とした以外は実施例１２と同様の操作を繰り返し、本例の担持用基材（実施粉末１５）を得た。
【００４９】
（比較例１）
粉末焼成温度を１０５０℃とした以外は実施例２と同様の操作を繰り返し、本例の担持用基材（比較粉末１）を得た。
【００５０】
（比較例２）
出発原料のＴｉ塩としてチタンイソプロポキシドを用いた以外は実施例２と同様の操作を繰り返し、本例の担持用基材（比較粉末２）を得た。
【００５１】
（比較例３）
粉末焼成温度を１０００℃、焼成時間を４時間とした以外は実施例５と同様の操作を繰り返し、本例の担持用基材（比較粉末３）を得た。
【００５２】
（比較例４）
出発原料のＴｉ塩として硫酸チタン塩を用いた以外は実施例２と同様の操作を繰り返し、本例の担持用基材（比較粉末４）を得た。
【００５３】
（実施例１６）
酸化アルミニウム換算粉末中に含まれる２原子分のＡｌに対して、０．１９原子分のＺｒ原子を含む酢酸ジルコニウム溶液と、０．１原子分のＭｇ原子を含む酢酸マグネシウムと、該当量のＡｌ原子を含む水酸化アルミニウムを水溶液中で攪拌し、乾燥し、次いで、空気気流中４００℃で１時間焼成し、Ｍｇ−Ａｌ複合酸化物の粉末を得た。
該Ｍｇ−Ａｌ複合酸化物粉末に含まれる２原子分のＡｌに対して、０．０１原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液を、該Ｍｇ−Ａｌ複合酸化物に含浸し、次いで、空気気流中１５０℃で２０時間乾燥した後、一旦粉砕し、しかる後、空気気流中９００℃で３時間焼成し、本例の担持用基材（実施粉末１６）を得た。
【００５４】
（実施例１７）
０．０３原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０３原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例１６と同様の操作を繰り返し、本例の担持用基材（実施粉末１７）を得た。
【００５５】
（実施例１８）
０．１９原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０５原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例１６と同様の操作を繰り返し、本例の担持用基材（実施粉末１８）を得た。
【００５６】
（実施例１９）
０．１５原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０１原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例１６と同様の操作を繰り返し、本例の担持用基材（実施粉末１９）を得た。
【００５７】
（実施例２０）
０．１０原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．１０原子分のＺｒ原子を含む酢酸ジルコニウム溶液と、０．２原子分のＭｇ原子を含む酢酸マグネシウム溶液を用い、粉末焼成温度を９５０℃とした以外は、実施例１６と同様の操作を繰り返し、本例の担持用基材（実施粉末２０）を得た。
【００５８】
（実施例２１）
０．２原子分のＭｇ原子を含む酢酸マグネシウム溶液を用い、粉末焼成温度を１０００℃とした以外は、実施例１６と同様の操作を繰り返し、本例の担持用基材（実施粉末２１）を得た。
【００５９】
（実施例２２）
０．２原子分のＭｇ原子を含む酢酸マグネシウム溶液を用い、粉末焼成温度を１０００℃とした以外は、実施例１７と同様の操作を繰り返し、本例の担持用基材（実施粉末２２）を得た。
【００６０】
（実施例２３）
０．０５原子分のＭｇ原子を含む酢酸マグネシウム溶液を用い、粉末焼成温度を１０００℃とした以外は、実施例１８と同様の操作を繰り返し、本例の担持用基材（実施粉末２３）を得た。
【００６１】
（実施例２４）
０．０５原子分のＭｇ原子を含む酢酸マグネシウム溶液を用い、粉末焼成温度を１０００℃とした以外は、実施例１９と同様の操作を繰り返し、本例の担持用基材（実施粉末２４）を得た。
【００６２】
（実施例２５）
０．０３原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０２原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用い、焼成温度を９００℃、焼成時間を２．５時間とした以外は、実施例１６と同様の操作を繰り返し、本例の担持用基材（実施粉末２５）を得た。
【００６３】
（実施例２６）
０．０１原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０６原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例２５と同様の操作を繰り返し、本例の担持用基材（実施粉末２６）を得た。
【００６４】
（実施例２７）
０．０９原子分のＴｉ原子を含むシュウ酸チタンアンモニウム溶液と、０．０１原子分のＺｒ原子を含む酢酸ジルコニウム溶液を用いた以外は、実施例２５と同様の操作を繰り返し、本例の担持用基材（実施粉末２７）を得た。
【００６５】
（実施例２８）
焼成温度を９５０℃、焼成時間を３時間とした以外は実施例２５と同様の操作を繰り返し、本例の担持用基材（実施粉末２８）を得た。
【００６６】
（実施例２９）
焼成温度を９５０℃、焼成時間を３時間とした以外は実施例２６と同様の操作を繰り返し、本例の担持用基材（実施粉末２９）を得た。
【００６７】
（実施例３０）
焼成温度を９５０℃、焼成時間を３時間とした以外は実施例２７と同様の操作を繰り返し、本例の担持用基材（実施粉末３０）を得た。
【００６８】
（比較例５）
Ｔｉ塩を使用せず、粉末焼成時間を０．５時間とした以外は実施例２４と同様の操作を繰り返し、本例の担持用基材（比較粉末５）を得た。
【００６９】
［排気ガス浄化触媒（粉末）］
（実施例３１）
上記実施粉末１に、触媒金属（貴金属）の出発原料としてジニトロジアミン白金硝酸酸性水溶液を含浸し、１５０℃で乾燥し、一旦粉砕し、次いで、空気気流中４００℃で１時間焼成し、貴金属を担持した本例の排気ガス浄化触媒を得た。このとき、Ｐｔの担持濃度は２％であった。
【００７０】
（実施例３２）
上記実施粉末２を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７１】
（実施例３３）
上記実施粉末３を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７２】
（実施例３４）
上記実施粉末４を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７３】
（実施例３５）
貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７４】
（実施例３６）
上記実施粉末２を用い、貴金属の出発原料として硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７５】
（実施例３７）
上記実施粉末３を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７６】
（実施例３８）
上記実施粉末４を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７７】
（実施例３９）
上記実施粉末５を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７８】
（実施例４０）
貴金属の出発原料として、硝酸パラジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００７９】
（実施例４１）
上記実施粉末２を用い、貴金属の出発原料として、硝酸パラジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８０】
（実施例４２）
上記実施粉末３を用い、貴金属の出発原料として、硝酸パラジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８１】
（実施例４３）
上記実施粉末４を用い、貴金属の出発原料として、硝酸パラジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８２】
（実施例４４）
上記実施粉末１０を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８３】
（実施例４５）
上記実施粉末１１を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８４】
（実施例４６）
上記実施粉末１２を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８５】
（実施例４７）
上記実施粉末１０を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８６】
（実施例４８）
上記実施粉末１１を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８７】
（実施例４９）
上記実施粉末１２を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８８】
（実施例５０）
上記実施粉末１３を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００８９】
（実施例５１）
上記実施粉末１４を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９０】
（実施例５２）
上記実施粉末１５を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９１】
（実施例５３）
上記実施粉末１６を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９２】
（実施例５４）
上記実施粉末１７を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９３】
（実施例５５）
上記実施粉末１８を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９４】
（実施例５６）
上記実施粉末１９を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９５】
（実施例５７）
上記実施粉末１６を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９６】
（実施例５８）
上記実施粉末２５を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９７】
（実施例５９）
上記実施粉末２６を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９８】
（実施例６０）
上記実施粉末２７を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【００９９】
（実施例６１）
上記実施粉末２５を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１００】
（実施例６２）
上記実施粉末２６を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０１】
（実施例６３）
上記実施粉末２７を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０２】
（実施例６４）
上記実施粉末２８を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０３】
（実施例６５）
上記実施粉末２９を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０４】
（実施例６６）
上記実施粉末３０を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０５】
（比較例６）
上記比較粉末１を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０６】
（比較例７）
上記比較粉末２を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０７】
（比較例８）
上記比較粉末３を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０８】
（比較例９）
上記比較粉末４を用い、貴金属の出発原料として、硝酸ロジウム水溶液を用いた以外は実施例３１と同様の操作を繰り返し、貴金属を担持した本例の排気ガス浄化触媒を得た。
【０１０９】
［性能評価］
実施例１９〜６６及び比較例６〜９の排気ガス浄化触媒を下記の性能評価に供した。
（ＸＲＤ分析）
各例の触媒を下記の条件下ＸＲＤによって分析した。得られた結果（Ｘ線回折パターン；２θ−ｄ表）を上記の表Ａ及び表Ｂの他、表５（表Ｃ）、表６（表Ｄ）に示す。
【０１１０】
・耐久条件
焼成温度 ９００℃
焼成時間 ３．０時間
焼成雰囲気 空気中
【０１１１】
【表５】
【表６】
実施例３１〜５２、比較例８及び９の触媒は表Ａ、実施例５３〜６６の触媒は表Ｂのパターンを示した。また、比較例６の触媒は表Ｃ、比較例７の触媒は表Ｄのパターンを示した。
【０１１５】
（貴金属分散度）
各例の触媒を下記の条件下で耐久処理した後、貴金属分散度を測定した。得られた結果を表７及び８に示す。また、各例の触媒仕様を表７及び８に併記する。
【０１１６】
・耐久条件
焼成温度 ７００℃
焼成時間 ３．０時間
焼成雰囲気 空気中
・貴金属分散度（ＰＭＳＡ）評価前処理条件
供試粉末を分取してサンプルフォルダに装着し、更に１０ｖｏｌ％酸素（Ｏ２）雰囲気下４００℃で１０分間酸化処理した。次いで、２ｖｏｌ％水素（Ｈ２）雰囲気下４００℃で１０分間還元処理した。しかる後、５０℃まで降温し、下記の評価を行った。
・ＰＭＳＡ評価条件
装置名 日本ベル社製、ＢＥＬ−ＭＥＴＡＬ−３
測定法 ＣＯパルス吸着法
測定温度 ５０℃
【０１１７】
【表７】
【表８】
表７及び８より、請求項１〜請求項４に記載の粉末を触媒金属担持基材に用いることにより、７００℃焼成後の貴金属分散度が向上し、劣化を抑制できることを確認し、特に請求項２又は４に記載の粉末を触媒金属担持基材に用いることが好ましいことが分かった。
【０１２０】
（モデルガス触媒評価試験）
また、実施例等の触媒粉末を数種類選択して、０．１２Ｌハニカム担体に各粉末スラリーをコーティングし、次いで、乾燥し、更に４００℃にて焼成した。下記の条件で耐久処理して熱劣化させた後、モデルガスによる触媒評価試験を行った。得られた結果を表９に示す。
【０１２１】
【表９】
以上、本発明を実施例により詳細に説明したが、本発明はこれら実施例に限定されるものではなく、本発明の要旨の範囲内で種々の変形が可能である。
例えば、上記試験例では、排気ガス浄化触媒を例にとって説明したが、本発明の触媒の用途はこれに限定されるものではなく、上述したように燃料電池用空気側電極触媒、更に燃料電池から排出される還元性ガスの浄化触媒などとしても使用可能である。
【０１２４】
【発明の効果】
以上説明してきたように、本発明によれば、チタンとジルコニア等を含有する特定の耐熱性無機複合酸化物を形成することなどとしたため、触媒活性成分の熱劣化を抑制し、触媒性能を向上し、使用する触媒活性成分の量を低減し得る触媒担持用基材、その製造方法及び該基材を用いた触媒を提供することができる。
【図面の簡単な説明】
【図１】本発明の触媒を自動車排気ガス用触媒に用いた一例を示す説明図である。
【図２】本発明の触媒を燃料電池電極触媒に用いた一例を示す説明図である。
【図３】本発明の触媒を廃水素燃焼器用触媒に用いた一例を示す説明図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a base material used for supporting a catalytically active component, and more particularly, has excellent heat resistance, suppresses sintering and solid solution of a noble metal even after durability, and has a good dispersion of a noble metal. The present invention relates to a substrate for supporting a catalyst, which maintains its properties, a method for producing the substrate, and a catalyst using the substrate.
[0002]
[Prior art]
Conventionally, various proposals have been made to suppress thermal deterioration (sintering, solid solution to a substrate, etc.) of a noble metal. For example, as a method of highly dispersing rhodium (Rh), a method of once forming a solid solution in alumina as a supporting base material and performing a reduction treatment has been proposed (for example, see Patent Document 1).
Further, it has been proposed to use an amorphous composite oxide containing an alkali metal element / alkaline earth metal element, alumina, titania, zirconia, silica, etc. as a substrate for supporting a high heat resistant catalyst (for example, And Patent Document 2.).
[0003]
[Patent Document 1]
JP-A-9-299796
[Patent Document 2]
JP-A-9-122486
[0004]
[Problems to be solved by the invention]
However, in the method described in
Further, even in the case of the substrate for supporting a high heat resistant catalyst described in Patent Document 2, it is difficult to say that the performance of suppressing the thermal deterioration of the noble metal is sufficient.
[0005]
The present invention has been made in view of such problems of the related art, and has as its object to suppress thermal degradation of a catalytically active component, improve catalytic performance, and improve the catalytically active component used. It is an object of the present invention to provide a catalyst-carrying substrate capable of reducing the amount, a method for producing the substrate, and a catalyst using the substrate.
[0006]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, found that the above object can be achieved by forming a specific heat-resistant inorganic composite oxide containing titanium, zirconia, and the like. The invention has been completed.
[0007]
That is, the substrate for supporting a catalyst of the present invention has the following formula (1)
[Ti] a [Zr] b [Al] cOx ... (1)
(Where a is 0.01 ≦ a ≦ 0.2, b is 0.01 ≦ b ≦ 0.2, c satisfies the relationship of c = 2-ab, and x satisfies the stoichiometry. X-rays containing a heat-resistant inorganic composite oxide having a composition represented by the following formula (specified in Table A above) after durability after supporting the catalytically active component. 3 shows a diffraction pattern (2θ-d value).
[0008]
Further, another catalyst-supporting substrate of the present invention has the following formula (2)
[Ti] a [Zr] b [α] c [Al] dOx ... (2)
(Where a is 0.01 ≦ a ≦ 0.2, b is 0.01 ≦ b ≦ 0.2, c is 0.01 ≦ c ≦ 0.2, and d is d = 2-ab- x is the number of oxygen that satisfies the stoichiometry, α is an alkaline earth metal element), and contains a heat-resistant inorganic composite oxide having a composition represented by the following formula: 2 shows a given X-ray diffraction pattern (specified in Table B above) after endurance after loading of the active ingredient.
[0009]
Further, the method for producing a substrate for supporting a catalyst of the present invention is a method for producing the above-described substrate for supporting a catalyst.
Depending on the type of the substrate for supporting the catalyst, firing is performed after impregnating alumina with a water-soluble titanium salt and zirconium acetate, or firing after impregnating alumina with a water-soluble titanium salt, zirconium acetate, and an alkaline earth metal salt.
[0010]
Furthermore, the catalyst of the present invention uses at least one of the catalyst-supporting substrates of the present invention, and one of the catalyst-supporting substrates or a mixture of both catalyst-supporting substrates contains a catalyst active component, In particular, it comprises a noble metal.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the catalyst supporting substrate of the present invention will be described in detail. In addition, in this specification, "%" represents a mass percentage unless otherwise specified.
[0012]
As described above, the base material for supporting a catalyst of the present invention is a base material used for supporting a catalytically active component, typically a noble metal, which includes an alkaline earth metal and an alkaline earth metal. There are types.
Here, the supporting base material containing no alkaline earth metal is expressed by the following formula (1).
[Ti] a [Zr] b [Al] cOx ... (1)
(Where a is 0.01 ≦ a ≦ 0.2, b is 0.01 ≦ b ≦ 0.2, c satisfies the relationship of c = 2-ab, and x satisfies the stoichiometry. The composition contains a heat-resistant inorganic composite oxide having a composition represented by the following formula:
Further, after durability after supporting the catalytically active component, typically, after standing in an air stream at 900 to 1000 ° C. for 1 to 3 hours, an X-ray diffraction pattern shown in the following Table A is shown.
[0013]
[Table 3]
In the formula (1), the atomic ratio of Ti or Zr to Al is 0.01 to 0.2 as shown by a or b, but if this atomic ratio exceeds 0.2, Ti or Zr becomes titania ( TiO 2 ) Or zirconia (ZrO) 2 ), A single oxide is formed and a composite oxide cannot be obtained, resulting in a decrease in specific surface area and making it impossible to modify the alumina surface.
On the other hand, if this atomic ratio is less than 0.01, a sufficient alumina reforming effect cannot be obtained, and it cannot contribute to the suppression of thermal deterioration of the noble metal which is a catalytically active component.
[0015]
The atomic ratio of Ti or Zr to Al is more preferably such that a is 0.02 ≦ a ≦ 0.09 and b is 0.01 ≦ b ≦ 0.07. This is generally the case for TiO 2 -ZrO 2 Is known to have the highest acid strength when mixed at the same molecular weight. 2 And ZrO 2 It is considered that when is mixed at around the same molecular weight, the bondability with the hydroxyl group on the alumina surface is the strongest, and it is easy to form a composite oxide with alumina.
When the atomic ratio of Ti to Al is in the range of 0.01 ≦ a ≦ 0.02, the reforming effect of alumina is obtained. For example, when the catalytically active component is Rh, the solid solution of Rh It is considered that an entrance-like site that can be a starting point remains. In the range of 0.09 ≦ a ≦ 0.2, a sufficient surface modification effect by Ti atoms is obtained, but slight TiO 2 2 Is formed as a single oxide on alumina, and in order to more effectively modify the alumina surface, the Ti atomic ratio is desirably 0.02 ≦ a ≦ 0.09.
[0016]
For the same reason, the atomic ratio of Zr to Al is more preferably 0.01 ≦ b ≦ 0.07. However, the molecular diameter is TiO 2 <ZrO 2 And ZrO having a relatively large molecular diameter. 2 Is TiO 2 The range over which the alumina surface can be effectively modified with respect to 2 Is likely to precipitate on the alumina surface, and it becomes difficult for the catalytically active component to be adsorbed on the alumina pores, so that the catalytic activity is likely to decrease.
In the formula (1), the oxygen atom ratio x is usually 2.
[0017]
The base material for supporting the catalyst is mainly composed of the composite oxide represented by the formula (1). However, it is not necessary that the whole substrate is composed of only the composite oxide. Titania, zirconia and alumina (Al 2 O 3 ) May partially be present. However, the whole substrate can be grasped uniformly and integrally, and in this sense, it can be called a substrate composition.
Further, the X-ray diffraction pattern shown in Table A above is shown for the entire substrate, and this pattern has specificity in the relative intensity ratio when compared with the composite oxide and the substrate outside the present invention (see below). See examples and comparative examples.) The specificity of this relative intensity ratio is consistent with the effect of suppressing the thermal degradation of alumina, and in the catalyst-carrying substrate of the present invention, even after the above-described endurance, the γ-alumina of the alumina is converted to the θ-alumina. It is difficult for the phase transition to proceed.
[0018]
In general, the thermal deterioration of the catalyst-supporting substrate is caused by sintering due to a series of phase transition of alumina, which is a main component, usually from γ-alumina to θ-alumina to α-alumina. Therefore, according to the supporting substrate of the present invention, for example, when the catalytically active component to be supported is Pt or Pd, it is possible to suppress the sintering caused by the decrease in the specific surface area that occurs when the substrate is sintered. In the case of Rh, solid solution in alumina can be suppressed.
The details of this effect are unknown at present, but can be guessed as follows.
That is, when Rh is supported on alumina to which nothing is added and fired at a high temperature, Rh is dissolved in the alumina. This phenomenon is generally known as a problem of the solid solution of Rh. Such solid solution of Rh is incorporated into the bulk (inside) of alumina when the supporting substrate undergoes a phase transition. It is considered that the amount of Rh that can be exposed on the catalyst surface (substrate surface) has decreased.
On the other hand, in the support substrate of the present invention, Ti and Zr atoms coexist on the alumina surface to modify the alumina surface. For example, the oxidation state of the noble metal accompanying the increase in the solid acid property of the substrate is improved. It can be speculated that the formation of an inlet-like site that can be a starting point of Rh solid solution on the substrate surface (alumina surface) is suppressed.
[0019]
Next, among the catalyst-supporting substrates of the present invention, those containing an alkaline earth metal element are represented by the following formula (2).
[Ti] a [Zr] b [α] c [Al] dOx ... (2)
(Where a is 0.01 ≦ a ≦ 0.2, b is 0.01 ≦ b ≦ 0.2, c is 0.01 ≦ c ≦ 0.2, and d is d = 2-ab- x is the number of oxygen that satisfies the stoichiometry, α is an alkaline earth metal element), and contains a heat-resistant inorganic composite oxide having a composition represented by the following formula: The line diffraction pattern is shown in Table B below.
[0020]
[Table 4]
In the formula (2), the reason for limiting the atomic ratio of Ti and Zr is the same as in the case of the formula (1), and the atomic ratio of Ti or Zr to Al is 0.01 ≦ a ≦ 0.09, b Is more preferably 0.01 ≦ b ≦ 0.06. The same applies to the point that the whole composite oxide does not need to be a complete compound, but the oxygen atom ratio x of this composite oxide is usually 4.
Further, as is apparent from the equation (2), this composite oxide further contains an alkaline earth metal element. As described above, by containing the alkaline earth metal element, the heat resistance of alumina can be further improved. However, if the alkaline earth metal element is simply included in the base material, oxygen is easily given to the noble metal, which may adversely affect the catalytic performance of the noble metal. In this regard, in the present invention, since the base material surface is modified with Ti or Zr as described above, by including an alkaline earth metal, the heat resistance of the base material can be effectively improved, and In addition, the catalytic performance of the noble metal can be further improved.
In the present invention, any alkaline earth metal element can be used alone or in any combination, but magnesium is particularly preferably used.
[0022]
Further, as described above, the substrate for supporting a catalyst containing the alkaline earth metal element shows the X-ray diffraction pattern shown in Table B after the durability, and differs in the crystallite diameter.
Such a difference in crystallite diameter indicates that the sintering of the base material powder is further suppressed in the supporting base material, and that the supporting base material has better heat resistance.
[0023]
Next, a method for producing the substrate for supporting a catalyst of the present invention will be described.
As described above, according to the production method of the present invention, a water-soluble titanium salt and zirconium acetate are used in the composite oxide of the formula (1) depending on the type of the composite oxide of the formula (1) or (2) to be obtained. In the composite oxide of the formula (2), an alkaline earth metal salt is further used, which is contained in alumina in an aqueous phase, dried, and fired.
Here, the use of the water-soluble Ti salt is such that when titanium-isopropoxide or the like, which is a water-insoluble Ti salt, is used, rutile-type titania crystals grow, and the modification of the alumina surface is sufficiently performed. This is because it is considered that the dispersibility of the noble metal decreases due to the failure. In general, alumina, which is a high specific surface inorganic oxide base material, has a large number of hydroxyl groups on its surface and is easily compatible with aqueous solvents. This is because it is desirable to use a water-soluble Ti salt that has a high affinity for the surface and enables titanium to be highly dispersed on the surface.
[0024]
In addition, it is desirable to use an organic carboxylic acid ammonium salt as the water-soluble Ti salt.
If other water-soluble salts such as sulfates and chlorides are used, sulfur and chlorine may remain in the catalyst even after calcination, and these may deactivate precious metals as catalyst poisons. On the other hand, when ammonium oxalates are used, they are all oxidatively decomposed into carbon dioxide and water after calcination, so that no element that can be a catalyst poison remains in the catalyst, and the formula (1) or (2) is used. And the performance of the composite oxide having a predetermined X-ray diffraction pattern can be sufficiently utilized, and a reduction in the catalytic activity of the noble metal can be effectively suppressed.
[0025]
For the impregnation of the zirconium component, zirconium acetate is used for the same reason as described above, but is not particularly limited as long as the above-mentioned problems can be avoided.
Further, as the alkaline earth metal salt, for the same selection reason as in the case of the titanium salt, these acetates, carbonates, nitrates, hydroxides and the like can be preferably used, but are not particularly limited. .
[0026]
The alumina is not particularly limited as long as it has a high specific surface area, but it is preferable to use γ-alumina in order to effectively prevent the adverse effect of thermal deterioration due to the phase transition of alumina.
Since the surface area of alumina decreases due to such thermal deterioration, in order to suppress a decrease in the catalytic performance of the supported noble metal, a decrease in the surface area of alumina, that is, in order to suppress a decrease in the surface area of the supporting substrate, a high specific surface area This is because it is desirable to use γ-alumina.
[0027]
The impregnation method is not particularly limited as long as Ti and Zr can be supported on alumina, but it is desirable to co-impregnate them.
According to the co-impregnation, the loading ratio of each component is easily controlled, and the number of steps can be reduced, so that the working efficiency is improved. It is considered that the deterioration of the material is small.
[0028]
When the alkaline earth metal is supported, one or both of Ti and Zr and the alkaline earth metal can be supported, and then one or both of Ti and Zr can be supported. The alkaline earth metal can be supported, and then Ti can be supported.
[0029]
The calcination treatment is not particularly limited as long as the above-described desired composite oxide is obtained. Typically, the calcination treatment is performed at 900 to 1000 ° C in an air stream for 1 to 3 hours, preferably at 900 to 950 ° C. Baking by heating for 2 to 3 hours.
If the firing temperature is lower than 900 ° C., the structure described in the claims cannot be obtained. If the firing temperature is higher than 1000 ° C., α-alumina having a low specific surface area may be generated.
If the time is less than 1 hour, the structure shown in the claim cannot be obtained, and even if it is fired for more than 3 hours, a desired composite oxide can be obtained, but it is not economical.
[0030]
In the production method of the present invention, drying may be performed before the baking treatment, and the obtained dry powder may be pulverized and then subjected to a baking treatment, whereby the uniformity of the base powder can be improved. .
[0031]
Next, the catalyst of the present invention will be described.
The catalyst of the present invention uses the above-described catalyst-supporting substrate of the present invention, and comprises at least one type of the supporting substrate specified by Formula (1) and Tables A, (2) and Table B. The substrate is used, and a catalytically active component such as a noble metal is supported on the substrate.
The catalyst of the present invention exhibits an excellent effect of suppressing deterioration of a noble metal from the advantage that the supporting substrate has excellent thermal stability as described above, and is particularly effective in an environment where the catalyst is exposed to an oxidizing atmosphere. .
Although the use is not particularly limited, the catalyst supporting substrate of the present invention is exposed to a high temperature and an oxidizing atmosphere for a long time due to the effect of suppressing the deterioration of the noble metal due to the excellent thermal stability of FIG. Particularly excellent effects can be exhibited by using the catalyst as an exhaust gas purifying catalyst for an automobile or the like as shown in FIG. Further, similarly, as an environment exposed to an oxidizing atmosphere, it is used as an electrode catalyst on the air electrode side in a fuel cell as shown in FIG. 2 or a purification catalyst for reducing gas discharged from the fuel cell as shown in FIG. Can be.
[0032]
Examples of the noble metal which is an example of the catalytically active component include Pt, Rh or Pd and an arbitrary mixture thereof, and the catalyst of the present invention has a remarkable effect of improving the solid solution of Rh.
The catalyst of the present invention can be used as it is, or can be used after being formed into granules or pellets, but can also be used by being supported on a monolithic carrier.
Examples of such a monolithic carrier include a monolith carrier and a honeycomb carrier made of a heat-resistant material such as a ceramic such as cordierite or a metal such as ferritic stainless steel.
[0033]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
[0034]
[Base material for supporting catalyst]
(Example 1)
A titanium ammonium oxalate solution containing 0.01 atom Ti atom and a zirconium acetate solution containing 0.19 atom Zr atom are oxidized with respect to 2 atom Al contained in the aluminum oxide powder. Aluminum powder was impregnated, then dried in an air stream at 150 ° C. for 20 hours, crushed once, and then calcined in an air stream at 900 ° C. for 3 hours to obtain a catalyst supporting substrate of this example (
[0035]
(Example 2)
The same operation as in Example 1 was repeated except that a titanium ammonium oxalate solution containing 0.03 atom of Ti atom and a zirconium acetate solution containing 0.03 atom of Zr atom were used. A supporting base material (Example powder 2) was obtained.
[0036]
(Example 3)
The same operation as in Example 1 was repeated except that a titanium ammonium oxalate solution containing 0.19 atom of Ti atom and a zirconium acetate solution containing 0.05 atom of Zr atom were used. A supporting substrate (Example powder 3) was obtained.
[0037]
(Example 4)
The same operation as in Example 1 was repeated except that a titanium ammonium oxalate solution containing 0.15 atom of Ti atom and a zirconium acetate solution containing 0.01 atom of Zr atom were used. A supporting substrate (Example powder 4) was obtained.
[0038]
(Example 5)
A titanium ammonium oxalate solution containing 0.1 atom of Ti atom and a zirconium acetate solution containing 0.1 atom of Zr atom were used, except that the powder firing temperature was 950 ° C. The operation was repeated to obtain a supporting substrate of this example (Example Powder 5).
[0039]
(Example 6)
The same operation as in Example 1 was repeated except that the powder sintering temperature was set to 1000 ° C. and the sintering time was set to 4 hours, to obtain a supporting substrate (Example powder 6) of this example.
[0040]
(Example 7)
The same operation as in Example 2 was repeated except that the powder sintering temperature was set to 1000 ° C. and the sintering time was set to 4 hours, to obtain a supporting substrate (Example powder 7) of this example.
[0041]
(Example 8)
The same operation as in Example 3 was repeated except that the powder sintering temperature was set to 1000 ° C. and the sintering time was set to 4 hours, to obtain a supporting substrate (Example powder 8) of this example.
[0042]
(Example 9)
The same operation as in Example 4 was repeated except that the powder sintering temperature was set to 1000 ° C. and the sintering time was set to 4 hours, to obtain a supporting substrate (Example powder 9) of this example.
[0043]
(Example 10)
Using a titanium ammonium oxalate solution containing 0.03 atom of Ti atom and a zirconium acetate solution containing 0.02 atom of Zr atom, except that the powder sintering temperature was 900 ° C. and the sintering time was 2.5 hours. The same operation as in Example 1 was repeated to obtain a supporting substrate (Example powder 10) of this example.
[0044]
(Example 11)
The same operation as in Example 10 was repeated except that a titanium ammonium oxalate solution containing 0.02 atom of Ti atom and a zirconium acetate solution containing 0.07 atom of Zr atom were used. A substrate for use (Example powder 11) was obtained.
[0045]
(Example 12)
The same operation as in Example 10 was repeated except that a titanium ammonium oxalate solution containing 0.09 atom of Ti atom and a zirconium acetate solution containing 0.01 atom of Zr atom were used. A substrate for use (Example powder 12) was obtained.
[0046]
(Example 13)
The same operation as in Example 10 was repeated, except that the firing temperature was 950 ° C. and the firing time was 3 hours, to obtain a supporting substrate (Example Powder 13) of this example.
[0047]
(Example 14)
The same operation as in Example 11 was repeated except that the firing temperature was 950 ° C. and the firing time was 3 hours, to obtain a supporting substrate (Example Powder 14) of this example.
[0048]
(Example 15)
The same operation as in Example 12 was repeated except that the firing temperature was 950 ° C. and the firing time was 3 hours, to obtain a supporting substrate (Example Powder 15) of this example.
[0049]
(Comparative Example 1)
The same operation as in Example 2 was repeated except that the powder sintering temperature was changed to 1050 ° C., to obtain a supporting substrate (Comparative Powder 1) of this example.
[0050]
(Comparative Example 2)
The same operation as in Example 2 was repeated except that titanium isopropoxide was used as the Ti salt as a starting material, to obtain a supporting substrate (Comparative Powder 2) of this example.
[0051]
(Comparative Example 3)
The same operation as in Example 5 was repeated except that the powder sintering temperature was set to 1000 ° C. and the sintering time was set to 4 hours, to obtain a supporting substrate (Comparative Powder 3) of this example.
[0052]
(Comparative Example 4)
The same operation as in Example 2 was repeated except that a titanium sulfate salt was used as a Ti salt as a starting material, to obtain a supporting substrate (Comparative Powder 4) of this example.
[0053]
(Example 16)
Zirconium acetate solution containing 0.19 atom of Zr atom, magnesium acetate containing 0.1 atom of Mg atom, and corresponding amount of Al with respect to 2 atom of Al contained in the aluminum oxide converted powder. The aluminum hydroxide containing atoms was stirred in an aqueous solution, dried, and then calcined at 400 ° C. for 1 hour in an air stream to obtain a powder of a Mg—Al composite oxide.
With respect to Al for 2 atoms contained in the Mg-Al composite oxide powder, a titanium ammonium oxalate solution containing 0.01 atomic Ti atom is impregnated into the Mg-Al composite oxide, After drying in an air stream at 150 ° C. for 20 hours, the mixture was once pulverized, and then calcined in an air stream at 900 ° C. for 3 hours to obtain a supporting substrate (Example Powder 16) of this example.
[0054]
(Example 17)
The same operation as in Example 16 was repeated except that a titanium ammonium oxalate solution containing 0.03 atom of Ti atom and a zirconium acetate solution containing 0.03 atom of Zr atom were used. A substrate for use (implementation powder 17) was obtained.
[0055]
(Example 18)
The same operation as in Example 16 was repeated, except that a titanium ammonium oxalate solution containing 0.19 atom of Ti atom and a zirconium acetate solution containing 0.05 atom of Zr atom were used. A base material for use (Example powder 18) was obtained.
[0056]
(Example 19)
The same operation as in Example 16 was repeated except that a titanium ammonium oxalate solution containing 0.15 atom of Ti atom and a zirconium acetate solution containing 0.01 atom of Zr atom were used. A substrate for use (implementation powder 19) was obtained.
[0057]
(Example 20)
Powder sintering using a titanium ammonium oxalate solution containing 0.10 atom of Ti atom, a zirconium acetate solution containing 0.10 atom of Zr atom, and a magnesium acetate solution containing 0.2 atom of Mg atom The same operation as in Example 16 was repeated, except that the temperature was changed to 950 ° C., to obtain a supporting substrate (Example powder 20) of this example.
[0058]
(Example 21)
The same operation as in Example 16 was repeated, except that the powder calcination temperature was set to 1000 ° C. using a magnesium acetate solution containing 0.2 atom of Mg atom, and the supporting substrate (executable powder 21) of this example was obtained. Obtained.
[0059]
(Example 22)
The same operation as in Example 17 was repeated, except that the powder sintering temperature was set to 1000 ° C. using a magnesium acetate solution containing 0.2 atoms of Mg atoms, and the supporting substrate of this example (Example powder 22) was prepared. Obtained.
[0060]
(Example 23)
The same operation as in Example 18 was repeated, except that the powder sintering temperature was set to 1000 ° C. using a magnesium acetate solution containing 0.05 atomic atoms of Mg atoms, and the supporting substrate of this example (Example powder 23) was prepared. Obtained.
[0061]
(Example 24)
The same operation as in Example 19 was repeated, except that the powder sintering temperature was set to 1000 ° C. using a magnesium acetate solution containing 0.05 atomic atoms of Mg atoms, and the supporting substrate of this example (executive powder 24) was prepared. Obtained.
[0062]
(Example 25)
Using a titanium ammonium oxalate solution containing 0.03 atom of Ti atom and a zirconium acetate solution containing 0.02 atom of Zr atom, except that the firing temperature was 900 ° C. and the firing time was 2.5 hours. The same operation as in Example 16 was repeated to obtain a supporting substrate (Example powder 25) of this example.
[0063]
(Example 26)
The same operation as in Example 25 was repeated except that a titanium ammonium oxalate solution containing 0.01 atom of Ti atom and a zirconium acetate solution containing 0.06 atom of Zr atom were used. A base material for use (Example powder 26) was obtained.
[0064]
(Example 27)
The same operation as in Example 25 was repeated except that a titanium ammonium oxalate solution containing 0.09 atom of Ti atom and a zirconium acetate solution containing 0.01 atom of Zr atom were used. A base material for use (implementation powder 27) was obtained.
[0065]
(Example 28)
The same operation as in Example 25 was repeated except that the firing temperature was 950 ° C. and the firing time was 3 hours, to obtain a supporting substrate (Example powder 28) of this example.
[0066]
(Example 29)
The same operation as in Example 26 was repeated except that the firing temperature was 950 ° C. and the firing time was 3 hours, to obtain a supporting substrate (Example powder 29) of this example.
[0067]
(Example 30)
The same operation as in Example 27 was repeated except that the firing temperature was 950 ° C. and the firing time was 3 hours, to obtain a supporting substrate (Example powder 30) of the present example.
[0068]
(Comparative Example 5)
The same operation as in Example 24 was repeated, except that the powder was fired for 0.5 hour without using the Ti salt, to obtain a supporting substrate (Comparative Powder 5) of this example.
[0069]
[Exhaust gas purification catalyst (powder)]
(Example 31)
The above working
[0070]
(Example 32)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 2 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0071]
(Example 33)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 3 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0072]
(Example 34)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 4 was used, to obtain an exhaust gas purifying catalyst of this example carrying a noble metal.
[0073]
(Example 35)
The same operation as in Example 31 was repeated except that an aqueous rhodium nitrate solution was used as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0074]
(Example 36)
The same operation as in Example 31 was repeated using the above-mentioned Example Powder 2 except that an aqueous rhodium nitrate solution was used as a starting material of the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0075]
(Example 37)
The same operation as in Example 31 was repeated using the above-described Example Powder 3 except that an aqueous rhodium nitrate solution was used as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0076]
(Example 38)
The same operation as in Example 31 was repeated using the above-mentioned Example Powder 4 and using an aqueous rhodium nitrate solution as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0077]
(Example 39)
The same operation as in Example 31 was repeated using the above-mentioned Example Powder 5 except that an aqueous rhodium nitrate solution was used as a starting material of the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0078]
(Example 40)
The same operation as in Example 31 was repeated except that an aqueous solution of palladium nitrate was used as a starting material for the noble metal, to obtain an exhaust gas purification catalyst of the present example carrying a noble metal.
[0079]
(Example 41)
The same operation as in Example 31 was repeated using the above-mentioned Example Powder 2 except that an aqueous solution of palladium nitrate was used as a starting material of the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0080]
(Example 42)
The same operation as in Example 31 was repeated using the above-mentioned Example Powder 3 except that an aqueous palladium nitrate solution was used as a starting material of the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0081]
(Example 43)
The same operation as in Example 31 was repeated using the above-described Example Powder 4 except that an aqueous solution of palladium nitrate was used as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0082]
(Example 44)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 10 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0083]
(Example 45)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 11 was used, to obtain an exhaust gas purifying catalyst of the present Example carrying a noble metal.
[0084]
(Example 46)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 12 was used, to obtain an exhaust gas purifying catalyst of this example carrying a noble metal.
[0085]
(Example 47)
The same operation as in Example 31 was repeated using the above-described Example Powder 10 except that an aqueous rhodium nitrate solution was used as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0086]
(Example 48)
The same operation as in Example 31 was repeated using the above-described Example Powder 11 and using an aqueous rhodium nitrate solution as a starting material for a noble metal, to obtain an exhaust gas purification catalyst of the present Example carrying a noble metal.
[0087]
(Example 49)
The same operation as in Example 31 was repeated using the above-described Example Powder 12 and using a rhodium nitrate aqueous solution as a starting material for a noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0088]
(Example 50)
The same operation as in Example 31 was repeated using the above-mentioned Example Powder 13 and using an aqueous rhodium nitrate solution as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0089]
(Example 51)
The same operation as in Example 31 was repeated using the above-mentioned Example Powder 14 and using an aqueous solution of rhodium nitrate as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0090]
(Example 52)
The same operation as in Example 31 was repeated by using the above-described Example Powder 15 and using an aqueous rhodium nitrate solution as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0091]
(Example 53)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 16 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0092]
(Example 54)
The same operation as in Example 31 was repeated, except that the above-mentioned Example Powder 17 was used, to obtain an exhaust gas purifying catalyst of this example carrying a noble metal.
[0093]
(Example 55)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 18 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0094]
(Example 56)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 19 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0095]
(Example 57)
The same operation as in Example 31 was repeated using the above-described Example Powder 16 except that an aqueous rhodium nitrate solution was used as a starting material of the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0096]
(Example 58)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 25 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0097]
(Example 59)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 26 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0098]
(Example 60)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 27 was used, to obtain an exhaust gas purifying catalyst of the present Example carrying a noble metal.
[0099]
(Example 61)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 25 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0100]
(Example 62)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 26 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0101]
(Example 63)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 27 was used, to obtain an exhaust gas purifying catalyst of the present Example carrying a noble metal.
[0102]
(Example 64)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 28 was used, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0103]
(Example 65)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 29 was used, to obtain an exhaust gas purifying catalyst of this example carrying a noble metal.
[0104]
(Example 66)
The same operation as in Example 31 was repeated except that the above-mentioned Example Powder 30 was used, to obtain an exhaust gas purifying catalyst of the present Example carrying a noble metal.
[0105]
(Comparative Example 6)
Using the
[0106]
(Comparative Example 7)
The same operation as in Example 31 was repeated using the above comparative powder 2 except that an aqueous rhodium nitrate solution was used as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0107]
(Comparative Example 8)
The same operation as in Example 31 was repeated using the above comparative powder 3 except that an aqueous rhodium nitrate solution was used as a starting material for the noble metal, to obtain an exhaust gas purifying catalyst of the present example carrying a noble metal.
[0108]
(Comparative Example 9)
Using the comparative powder 4, the same operation as in Example 31 was repeated except that an aqueous rhodium nitrate solution was used as a starting material for the noble metal, to obtain an exhaust gas purification catalyst of the present example carrying a noble metal.
[0109]
[Performance evaluation]
The exhaust gas purifying catalysts of Examples 19 to 66 and Comparative Examples 6 to 9 were subjected to the following performance evaluations.
(XRD analysis)
The catalyst of each example was analyzed by XRD under the following conditions. The obtained results (X-ray diffraction pattern; 2θ-d table) are shown in Tables 5 (Table C) and 6 (Table D) in addition to Tables A and B described above.
[0110]
・ Durability conditions
Firing temperature 900 ℃
Firing time 3.0 hours
Firing atmosphere In air
[0111]
[Table 5]
[Table 6]
The catalysts of Examples 31 to 52 and Comparative Examples 8 and 9 showed the patterns of Table A, and the catalysts of Examples 53 to 66 showed the patterns of Table B. The catalyst of Comparative Example 6 showed the pattern of Table C, and the catalyst of Comparative Example 7 showed the pattern of Table D.
[0115]
(Noble metal dispersion)
After the catalyst of each example was subjected to durability treatment under the following conditions, the degree of dispersion of the noble metal was measured. The results obtained are shown in Tables 7 and 8. Tables 7 and 8 also show the catalyst specifications of each example.
[0116]
・ Durability conditions
Firing temperature 700 ℃
Firing time 3.0 hours
Firing atmosphere In air
・ Pretreatment conditions for precious metal dispersion (PMSA) evaluation
The powder to be tested was collected and attached to a sample folder, and further 10 vol% oxygen (O 2 ) Oxidation treatment was performed at 400 ° C for 10 minutes in an atmosphere. Then, 2 vol% hydrogen (H 2 ) Reduction treatment was performed at 400 ° C for 10 minutes in an atmosphere. Thereafter, the temperature was lowered to 50 ° C., and the following evaluation was performed.
・ PMSA evaluation conditions
Device name BEL-METAL-3 manufactured by Japan Bell Co., Ltd.
Measurement method CO pulse adsorption method
Measurement temperature 50 ° C
[0117]
[Table 7]
[Table 8]
From Tables 7 and 8, it was confirmed that the use of the powder according to any one of
[0120]
(Model gas catalyst evaluation test)
Further, several kinds of catalyst powders of Examples and the like were selected, each powder slurry was coated on a 0.12 L honeycomb carrier, dried, and further fired at 400 ° C. After being subjected to a durability treatment under the following conditions to be thermally degraded, a catalyst evaluation test using a model gas was performed. Table 9 shows the obtained results.
[0121]
[Table 9]
As described above, the present invention has been described in detail with reference to the examples. However, the present invention is not limited to these examples, and various modifications can be made within the scope of the present invention.
For example, in the above test example, the exhaust gas purifying catalyst was described as an example, but the use of the catalyst of the present invention is not limited to this. As described above, the fuel cell air-side electrode catalyst, It can also be used as a catalyst for purifying discharged reducing gas.
[0124]
【The invention's effect】
As described above, according to the present invention, since a specific heat-resistant inorganic composite oxide containing titanium, zirconia, and the like is formed, the thermal degradation of the catalytically active component is suppressed, and the catalytic performance is improved. In addition, it is possible to provide a catalyst supporting substrate capable of reducing the amount of a catalytically active component used, a method for producing the same, and a catalyst using the substrate.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example in which the catalyst of the present invention is used as a catalyst for automobile exhaust gas.
FIG. 2 is an explanatory diagram showing an example in which the catalyst of the present invention is used as a fuel cell electrode catalyst.
FIG. 3 is an explanatory diagram showing an example in which the catalyst of the present invention is used as a catalyst for a waste hydrogen combustor.
Claims (12)
［Ｔｉ］ａ［Ｚｒ］ｂ［Ａｌ］ｃＯｘ…▲１▼
（式中のａは０．０１≦ａ≦０．２、ｂは０．０１≦ｂ≦０．２、ｃはｃ＝２−ａ−ｂの関係を満足し、ｘは化学量論を満たす酸素数を示す。）で表される組成を有する耐熱性無機複合酸化物を含有し、
触媒活性成分を担持した後の耐久後におけるＸ線回折パターンが、次の表Ａで表されることを特徴とする触媒担持用基材。
[Ti] a [Zr] b [Al] cOx ... (1)
(Where a is 0.01 ≦ a ≦ 0.2, b is 0.01 ≦ b ≦ 0.2, c satisfies the relationship of c = 2-ab, and x satisfies the stoichiometry. Containing a heat-resistant inorganic composite oxide having a composition represented by the following formula:
A substrate for supporting a catalyst, wherein the X-ray diffraction pattern after durability after supporting the catalytically active component is shown in Table A below.
［Ｔｉ］ａ［Ｚｒ］ｂ［α］ｃ［Ａｌ］ｄＯｘ…▲２▼
（式中のａは０．０１≦ａ≦０．２、ｂは０．０１≦ｂ≦０．２、ｃは０．０１≦ｃ≦０．２、ｄはｄ＝２−ａ−ｂ−ｃの関係を満足し、ｘは化学量論を満たす酸素数、αはアルカリ土類金属元素を示す。）で表される組成を有する耐熱性無機複合酸化物を含有し、
触媒活性成分を担持した後の耐久後におけるＸ線回折パターンが、次の表Ｂで表されることを特徴とする触媒担持用基材。
[Ti] a [Zr] b [α] c [Al] dOx ... (2)
(Where a is 0.01 ≦ a ≦ 0.2, b is 0.01 ≦ b ≦ 0.2, c is 0.01 ≦ c ≦ 0.2, and d is d = 2-ab- x is the number of oxygen that satisfies the stoichiometry, α is an alkaline earth metal element), and contains a heat-resistant inorganic composite oxide having a composition represented by the following formula:
An X-ray diffraction pattern after durability after supporting the catalytically active component is shown in the following Table B. A substrate for supporting a catalyst, characterized in that:
水溶性チタン塩と酢酸ジルコニウムをアルミナに含浸し、次いで、焼成することを特徴とする触媒担持用基材の製造方法。In producing the catalyst supporting substrate according to claim 1 or 2,
A method for producing a catalyst-carrying substrate, comprising impregnating alumina with a water-soluble titanium salt and zirconium acetate, and then firing.
水溶性チタン塩と酢酸ジルコニウムとアルカリ土類金属塩をアルミナに含浸し、次いで、焼成することを特徴とする触媒担持用基材の製造方法。In producing the substrate for supporting a catalyst according to claim 3 or 4,
A method for producing a substrate for supporting a catalyst, comprising impregnating alumina with a water-soluble titanium salt, zirconium acetate, and an alkaline earth metal salt, followed by firing.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100397694C (en) * | 2005-01-21 | 2008-06-25 | 三星Sdi株式会社 | Support for fuel reforming catalyst with excellent heat and mass transfer characteristics and method of preparing the same |
| JP2013046913A (en) * | 2012-11-22 | 2013-03-07 | Showa Denko Kk | Electrode catalyst and use thereof, and method for manufacturing the electrode catalyst |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100397694C (en) * | 2005-01-21 | 2008-06-25 | 三星Sdi株式会社 | Support for fuel reforming catalyst with excellent heat and mass transfer characteristics and method of preparing the same |
| JP2013046913A (en) * | 2012-11-22 | 2013-03-07 | Showa Denko Kk | Electrode catalyst and use thereof, and method for manufacturing the electrode catalyst |
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