JP4928931B2 - Ceria-zirconia composite oxide and method for producing the same - Google Patents
Ceria-zirconia composite oxide and method for producing the same Download PDFInfo
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- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 title claims description 90
- 239000002131 composite material Substances 0.000 title claims description 78
- 238000004519 manufacturing process Methods 0.000 title claims description 14
- -1 cerium (III) ions Chemical class 0.000 claims description 73
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 52
- 239000000243 solution Substances 0.000 claims description 52
- 239000002002 slurry Substances 0.000 claims description 30
- 125000005385 peroxodisulfate group Chemical group 0.000 claims description 20
- 239000011164 primary particle Substances 0.000 claims description 20
- 229910052726 zirconium Inorganic materials 0.000 claims description 20
- 229910052684 Cerium Inorganic materials 0.000 claims description 17
- 238000010304 firing Methods 0.000 claims description 16
- 239000003929 acidic solution Substances 0.000 claims description 14
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical compound Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 claims description 14
- CMOAHYOGLLEOGO-UHFFFAOYSA-N oxozirconium;dihydrochloride Chemical compound Cl.Cl.[Zr]=O CMOAHYOGLLEOGO-UHFFFAOYSA-N 0.000 claims description 14
- 238000001354 calcination Methods 0.000 claims description 12
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 12
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 11
- MLHCSEGGTGAQHZ-UHFFFAOYSA-G [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Zr+4].[Ce+3] Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Zr+4].[Ce+3] MLHCSEGGTGAQHZ-UHFFFAOYSA-G 0.000 claims description 10
- 238000007254 oxidation reaction Methods 0.000 claims description 10
- 230000003647 oxidation Effects 0.000 claims description 8
- 230000001590 oxidative effect Effects 0.000 claims description 8
- XQTIWNLDFPPCIU-UHFFFAOYSA-N cerium(3+) Chemical compound [Ce+3] XQTIWNLDFPPCIU-UHFFFAOYSA-N 0.000 claims description 6
- 229910052773 Promethium Inorganic materials 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- 150000002500 ions Chemical class 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 5
- 230000001376 precipitating effect Effects 0.000 claims description 5
- VQMWBBYLQSCNPO-UHFFFAOYSA-N promethium atom Chemical compound [Pm] VQMWBBYLQSCNPO-UHFFFAOYSA-N 0.000 claims description 5
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 5
- 229910052706 scandium Inorganic materials 0.000 claims description 5
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 claims description 5
- 229910052727 yttrium Inorganic materials 0.000 claims description 5
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 5
- GBNDTYKAOXLLID-UHFFFAOYSA-N zirconium(4+) ion Chemical compound [Zr+4] GBNDTYKAOXLLID-UHFFFAOYSA-N 0.000 claims description 5
- ITZXULOAYIAYNU-UHFFFAOYSA-N cerium(4+) Chemical compound [Ce+4] ITZXULOAYIAYNU-UHFFFAOYSA-N 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims 2
- 239000002253 acid Substances 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 35
- 238000000034 method Methods 0.000 description 23
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 18
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 18
- 239000003054 catalyst Substances 0.000 description 16
- 239000002245 particle Substances 0.000 description 15
- 238000003756 stirring Methods 0.000 description 15
- 239000000843 powder Substances 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 239000011259 mixed solution Substances 0.000 description 11
- 238000002156 mixing Methods 0.000 description 11
- 239000000203 mixture Substances 0.000 description 11
- 238000006386 neutralization reaction Methods 0.000 description 9
- 239000002244 precipitate Substances 0.000 description 9
- 229910002651 NO3 Inorganic materials 0.000 description 8
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 8
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical compound [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 8
- 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 8
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 7
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 7
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 7
- 235000011130 ammonium sulphate Nutrition 0.000 description 7
- 239000012935 ammoniumperoxodisulfate Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 7
- 239000013078 crystal Substances 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- 238000000746 purification Methods 0.000 description 7
- 238000005406 washing Methods 0.000 description 7
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 6
- 235000011114 ammonium hydroxide Nutrition 0.000 description 6
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 5
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 5
- 239000003513 alkali Substances 0.000 description 5
- 239000002585 base Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000000470 constituent Substances 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 4
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 4
- 239000003426 co-catalyst Substances 0.000 description 4
- 238000010981 drying operation Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000003795 desorption Methods 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 150000004679 hydroxides Chemical class 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 2
- QRTRRDMHGTZPBF-UHFFFAOYSA-L oxygen(2-);zirconium(4+);sulfate Chemical compound [O-2].[Zr+4].[O-]S([O-])(=O)=O QRTRRDMHGTZPBF-UHFFFAOYSA-L 0.000 description 2
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Chemical compound [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 2
- 238000003860 storage Methods 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
- 229910001928 zirconium oxide Inorganic materials 0.000 description 2
- ZXAUZSQITFJWPS-UHFFFAOYSA-J zirconium(4+);disulfate Chemical compound [Zr+4].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZXAUZSQITFJWPS-UHFFFAOYSA-J 0.000 description 2
- IVORCBKUUYGUOL-UHFFFAOYSA-N 1-ethynyl-2,4-dimethoxybenzene Chemical compound COC1=CC=C(C#C)C(OC)=C1 IVORCBKUUYGUOL-UHFFFAOYSA-N 0.000 description 1
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- 150000000703 Cerium Chemical class 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 229910017493 Nd 2 O 3 Inorganic materials 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- JGDITNMASUZKPW-UHFFFAOYSA-K aluminium trichloride hexahydrate Chemical compound O.O.O.O.O.O.Cl[Al](Cl)Cl JGDITNMASUZKPW-UHFFFAOYSA-K 0.000 description 1
- 229940063656 aluminum chloride Drugs 0.000 description 1
- 229940009861 aluminum chloride hexahydrate Drugs 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000002981 blocking agent Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- VFNGKCDDZUSWLR-UHFFFAOYSA-L disulfate(2-) Chemical compound [O-]S(=O)(=O)OS([O-])(=O)=O VFNGKCDDZUSWLR-UHFFFAOYSA-L 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 1
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
- 229910052939 potassium sulfate Inorganic materials 0.000 description 1
- 235000011151 potassium sulphates Nutrition 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 238000001226 reprecipitation Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
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- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Catalysts (AREA)
Description
本発明は、触媒、紫外線遮断剤、電極材料、燃料電池用固体電解質分野に利用可能であり、特に自動車の排ガス浄化用触媒における助触媒として使用されるセリア−ジルコニア系複合酸化物およびその製造方法に関する。 INDUSTRIAL APPLICABILITY The present invention can be used in the field of catalysts, ultraviolet blocking agents, electrode materials, solid electrolytes for fuel cells, and in particular, a ceria-zirconia composite oxide used as a co-catalyst in automobile exhaust gas purification catalysts and a method for producing the same About.
セリアは酸素吸蔵放出能（Oxygen Storage Capacity、以下単に「ＯＳＣ」という）を有するため、自動車排ガス浄化用触媒の助触媒として広く用いられている。これはＣｅ３＋／Ｃｅ４＋のレドックス反応を利用したものである。このセリアは、一般にその特性を高めるためセリア−ジルコニア系複合酸化物として使用されている。 Since ceria has an oxygen storage capacity (Oxygen Storage Capacity, hereinafter simply referred to as “OSC”), it is widely used as a promoter for automobile exhaust gas purification catalysts. This utilizes the redox reaction of Ce 3+ / Ce 4+ . This ceria is generally used as a ceria-zirconia composite oxide in order to enhance its properties.
近年、環境意識の高まりから自動車排ガス用触媒もエンジン始動直後から触媒性能を発揮することが求められ、浄化活性温度を確保するため触媒搭載位置が年々エンジンに近くなっている。このため、触媒は９００〜９５０℃の高温にさらされることとなり、触媒担体には１２００℃での耐酸化性、耐熱衝撃性が要求されている（非特許文献１参照）。 In recent years, due to increasing environmental awareness, automobile exhaust gas catalysts are also required to exhibit catalytic performance immediately after engine startup, and the catalyst mounting position is becoming closer to the engine year by year in order to ensure a purification activation temperature. For this reason, the catalyst is exposed to a high temperature of 900 to 950 ° C., and the catalyst carrier is required to have oxidation resistance and thermal shock resistance at 1200 ° C. (see Non-Patent Document 1).
このセリア−ジルコニア系複合酸化物は、その上に触媒貴金属が担持された状態でアルミナに数％ないし数十％の割合で混合され、ハニカム担体表面に十数μｍないし数百μｍの厚さのウォッシュコート層に形成され、助触媒として機能するようになっている。 This ceria-zirconia-based composite oxide is mixed with alumina in a ratio of several percent to several tens of percent with a catalyst noble metal supported thereon, and has a thickness of several tens to several hundreds of μm on the honeycomb carrier surface. It is formed in the washcoat layer and functions as a promoter.
このウォッシュコート層中のアルミナは耐熱性が高く高温でも粒子成長が少ないが、助触媒として機能するセリア−ジルコニア系複合酸化物は高温で粒子成長を起こしやすく、従来のセリア−ジルコニア系複合酸化物は、１２００℃の高温にさらされると一次粒子径が１０００℃における粒子径の１０倍程度まで大きくなるという現象があり、ウォッシュコート層の破壊、脱落の原因となると指摘されてきた。 The alumina in this washcoat layer has high heat resistance and little particle growth even at high temperatures, but the ceria-zirconia composite oxide that functions as a co-catalyst tends to cause particle growth at high temperatures, and the conventional ceria-zirconia composite oxide It has been pointed out that when exposed to a high temperature of 1200 ° C., the primary particle size increases to about 10 times the particle size at 1000 ° C., which causes the washcoat layer to break down and fall off.
このためウォッシュコート層へのセリア−ジルコニア系複合酸化物の配合量が制限されていた。すなわち、セリア−ジルコニア系複合酸化物が粒子成長を起こすときには、ウォッシュコート層内でセリア−ジルコニア系複合酸化物粒子がもともと存在していた位置に空孔が生じる一方、他の部位では粒子成長による強いストレスが生じ、一般に粒子系が２００ｎｍ以上となるとウォッシュコート層の破壊、脱落が生ずるといわれている。さらにセリア−ジルコニア系複合酸化物粒子の成長に伴う表面積の減少により、セリア−ジルコニア系複合酸化物粒子上に担持されている触媒貴金属のシンタリングが進み、触媒活性が低下するという問題があり、高温で使用される自動車排ガス触媒では予め触媒貴金属量を増やしておくなどの対策が必要となり、貴金属の高騰とともにその経済性の改善が強く求められていた。 For this reason, the compounding quantity of the ceria-zirconia type complex oxide to the washcoat layer has been limited. That is, when the ceria-zirconia composite oxide undergoes particle growth, vacancies are generated at the position where the ceria-zirconia composite oxide particles originally existed in the washcoat layer. It is said that when a strong stress is generated and the particle size is 200 nm or more, the washcoat layer is broken or dropped off. Furthermore, due to the decrease in the surface area accompanying the growth of the ceria-zirconia composite oxide particles, there is a problem that the sintering of the catalyst noble metal carried on the ceria-zirconia composite oxide particles proceeds and the catalytic activity decreases, For automobile exhaust gas catalysts that are used at high temperatures, measures such as increasing the amount of precious metal in the catalyst in advance are required, and there has been a strong demand for improvement in economic efficiency along with soaring precious metals.
セリア−ジルコニア系複合酸化物の製造方法としては、いわゆる中和沈殿法として非特許文献２に示されているように、硝酸塩にいわゆる第３成分を加え、アンモニアで中和して得られる水酸化物をろ過、洗浄後、焼成する方法が公知である。また、耐熱性に優れたセリア−ジルコニア系複合酸化物の製造方法としては、例えば特許文献１にはセリウム(IV)溶液とジルコニウム溶液を混合して熱加水分解する方法が、特許文献２には水酸化ジルコニウム粒子とセリウムゾルを硝酸存在下で加熱して溶解、再析出反応を行い、塩基を加えてさらに反応させ、得られた生成物を焼成、粉砕する方法が、特許文献３には塩基性硫酸ジルコニウムとセリウムイオンを含む溶液とを混合した後、塩基を添加しｐＨを１２以上１４未満とすることにより沈殿物を生成させる方法が、特許文献４には、硫酸根の存在下にアルカリを添加し、その反応混合物中にセリウム塩溶液を添加し、得られた混合物を反応させてジルコニア−セリア基複合水酸化物を形成せしめる方法が記載されている。
As a method for producing a ceria-zirconia composite oxide, as shown in Non-Patent Document 2 as a so-called neutralization precipitation method, a so-called third component is added to nitrate and neutralized with ammonia. A method of firing after filtering and washing an object is known. As a method for producing a ceria-zirconia composite oxide having excellent heat resistance, for example,
しかしながら、工業的にもっとも安価に製造できると思われる中和沈殿法で得られるセリア−ジルコニア系複合酸化物は、非特許文献１によれば、７５０℃では８０ｍ２／ｇ程度であった比表面積が１，０００℃、３ｈの焼成後には２０ｍ２／ｇ以下と急落しており耐熱性が不十分である。一方、特許文献１に示されているセリウム（IV）溶液とジルコニウム溶液とを混合して熱加水分解する方法では、反応に長い時間がかかる上、その後の処理も複雑で製品が得られるまでに非常に時間がかかりコスト的に不利である。特許文献２に示されている硝酸存在下で加熱する方法では、ジルコニアゾル調整が不要なもののセリウムゾルの調整が必要であり、反応温度も高いためコスト的に不利である。特許文献３に示されている塩基性硫酸ジルコニウムとセリウムイオンを含む溶液を混合する方法、特許文献４に示されている硫酸根存在下にアルカリを添加する方法は、ともに、一旦ジルコニウムの沈殿を生成せしめた後にセリウムを沈殿させており原子レベルでの混合が悪く複合酸化物といい難いという問題がある。また、上記いずれの非特許文献、特許文献においては、すべての実施例において硝酸系の原料を使用しており、窒素排水規制の強化が行われている近年では工業規模で生産する場合、硝酸イオンを処理する特別な工程が必要となりコスト的に大きな負担となる。
However, according to
さらに、これら特許文献１〜４により製造されるセリア−ジルコニア系複合酸化物は、１０００℃における一次粒子径が大きく、かつ後の高温下での成長率も大きく、そのため、先述の高温使用時におけるウォッシュコート層の破壊、脱落を避けがたいという問題がある。
Furthermore, the ceria-zirconia-based composite oxide produced according to these
本発明は、これら従来技術の有する問題点を解決することを目的とし、特にエンジン近傍で使用される自動車の排ガス浄化用触媒における助触媒として優れた特性を有するセリアとジルコニア系複合酸化物およびその製造方法を提供することを目的とする。また、本発明は、基本製造プロセスとして工業的にもっとも安価に製造できる中和沈殿法を採用して、排水に硝酸イオンが含まれない低コストでかつ耐熱性が高いセリア−ジルコニア系複合酸化物及びその製造方法を提案することを目的とする。 The present invention aims to solve these problems of the prior art, and in particular, a ceria and zirconia composite oxide having excellent characteristics as a promoter in an exhaust gas purification catalyst for automobiles used in the vicinity of the engine, and its An object is to provide a manufacturing method. In addition, the present invention adopts a neutralization precipitation method that can be produced industrially at the lowest cost as a basic production process, and is a low-cost and high heat-resistant ceria-zirconia-based composite oxide that does not contain nitrate ions in the wastewater. And it aims at proposing the manufacturing method.
本発明者は、上記の目的を達成するためには、セリア−ジルコニア系複合酸化物の製造過程において、原子レベルでの高い混合状態を得ることが必要なことに着目し、そのための手段として硫酸イオンの存在の下でセリウム（IV）イオン及びジルコニウム（IV）イオンを硫酸塩として同時に沈殿させることが極めて有効であることを見出し、また、それによって得られるセリア−ジルコニア系複合酸化物が、エンジン近傍で使用される自動車の排ガス浄化用触媒における助触媒として優れた特性を有していることを確認した。 In order to achieve the above object, the present inventor has paid attention to the necessity of obtaining a high mixed state at the atomic level in the production process of the ceria-zirconia composite oxide. It has been found that it is extremely effective to simultaneously precipitate cerium (IV) ions and zirconium (IV) ions as sulfates in the presence of ions, and the ceria-zirconia composite oxide obtained thereby is used in an engine. It has been confirmed that it has excellent characteristics as a promoter in an automobile exhaust gas purification catalyst used in the vicinity.
本発明のセリア−ジルコニア系複合酸化物は、１２００℃で１２時間焼成後の一次粒子径が２００ｎｍ以下である点に特徴がある。ここに一次粒子径とは、日刊工業新聞社発行「粒度測定技術」第２３１頁に記載の比表面積径Ｄｗ（単位：ｎｍ）によるものであり、(1)式を用いて算出したものである。
Ｄｗ＝６０００／（ｓ×ρ）・・・・・・（１）
ここに
ｓ：比表面積(単位：ｍ２／ｇ)
ρ：密度（単位：ｇ／ｃｍ３）
であり、セリア−ジルコニア固溶体の密度は構成酸化物の組成により重みつけをした平均密度を用い、比表面積は窒素ガス吸着によるＢＥＴ法による測定結果である。
The ceria-zirconia composite oxide of the present invention is characterized in that the primary particle diameter after firing at 1200 ° C. for 12 hours is 200 nm or less. Here, the primary particle diameter is based on the specific surface area diameter Dw (unit: nm) described in “Particle Size Measurement Technology”, page 231 issued by Nikkan Kogyo Shimbun, and is calculated using the equation (1). .
Dw = 6000 / (s × ρ) (1)
Where s: specific surface area (unit: m 2 / g)
ρ: density (unit: g / cm 3 )
The density of the ceria-zirconia solid solution is an average density weighted by the composition of the constituent oxide, and the specific surface area is a measurement result by a BET method by nitrogen gas adsorption.
上記発明において、１２００℃で１２時間焼成後の一次粒子径が１０００℃で１２時間焼成後の一次粒子径の３倍以下であることとするのが好ましい。 In the said invention, it is preferable that the primary particle diameter after baking at 1200 degreeC for 12 hours is 3 times or less of the primary particle diameter after baking for 12 hours at 1000 degreeC.
上記セリア−ジルコニア系複合酸化物は、アルミニウム、スカンジウム、イットリウム及び原子番号５７〜７１までの希土類元素（プロメチウムを除く）から選択され、安定な酸化物を形成するときの酸化数が３となる１種又は２種以上の元素を第三成分として含有するものとすることができる。 The ceria-zirconia-based composite oxide is selected from aluminum, scandium, yttrium, and rare earth elements (excluding promethium) having an atomic number of 57 to 71, and has an oxidation number of 3 when forming a stable oxide. A seed or two or more elements may be contained as a third component.
上記セリア−ジルコニア系複合酸化物は、塩化セリウム及びオキシ塩化ジルコニウムを原料としてセリウム（III）イオン及びジルコニウムイオンを含有する酸性溶液を準備する第１段階と、前記酸性溶液にペルオキソ二硫酸塩を添加してセリウム（III）イオンをセリウム（IV）イオンに酸化する第２段階と、前記第２段階で得られたセリウム（IV）イオンと前記第２段階において未反応のペルオキソ二硫酸塩を含む溶液を加熱してセリウム（IV）イオン及びジルコニウムイオンを硫酸塩として沈殿させスラリー溶液を得る第３段階と、前記第３段階で得られたスラリー溶液に塩基を添加してセリウム−ジルコニウム系水酸化物スラリーを得る第４段階と、前記セリウム−ジルコニウム系水酸化物スラリーを固液分離後、洗浄、乾燥及び焼成す第５段階とを行うことによって製造することができる。 The ceria-zirconia-based composite oxide includes a first step of preparing an acidic solution containing cerium (III) ions and zirconium ions using cerium chloride and zirconium oxychloride as raw materials, and adding peroxodisulfate to the acidic solution A second stage for oxidizing cerium (III) ions to cerium (IV) ions, and a solution containing cerium (IV) ions obtained in the second stage and peroxodisulfate unreacted in the second stage A third stage for precipitating cerium (IV) ions and zirconium ions as sulfate to obtain a slurry solution, and adding a base to the slurry solution obtained in the third stage to obtain a cerium-zirconium hydroxide A fourth step of obtaining a slurry; and a step of washing, drying and calcining the cerium-zirconium hydroxide slurry after solid-liquid separation. It can be prepared by performing the steps.
前記セリウム(III)イオンをセリウム（IV）イオンに酸化する第２段階において、ペルオキソ二硫酸塩とともに硫酸塩を添加することができる。 In the second step of oxidizing the cerium (III) ion to cerium (IV) ion, sulfate can be added together with peroxodisulfate.
前記セリウム(III)イオンをセリウム（IV）イオンに酸化する第２段階において、ペルオキソ二硫酸塩の全部又は一部を過酸化水素に代替するとともに該第２段階又はそれに第３段階においてセリウム（IV）イオン及びジルコニウムイオンの全てを硫酸塩として沈殿させるに必要な硫酸塩を添加することができる。 In the second step of oxidizing the cerium (III) ions to cerium (IV) ions, all or part of the peroxodisulfate is replaced with hydrogen peroxide, and cerium (IV) is used in the second or third step. ) Sulfate necessary to precipitate all ions and zirconium ions as sulfate can be added.
セリウム（III）イオン及びジルコニウムイオンを含む酸性溶液には、アルミニウム、スカンジウム、イットリウム及び原子番号５７〜７１までの希土類元素（プロメチウムを除く）から選択され、安定な酸化物を形成するときの酸化数が３となる１種又は２種以上の元素を第三成分として含有させることとすることができる。 The acidic solution containing cerium (III) ion and zirconium ion is selected from aluminum, scandium, yttrium, and rare earth elements (excluding promethium) up to atomic number 57 to 71, and the oxidation number when forming a stable oxide. 1 type or 2 types or more elements in which is 3 can be contained as a third component.
本発明に係るセリア−ジルコニア系複合酸化物は、エンジン近傍で使用される自動車の排ガス浄化用触媒における助触媒として使用されたときにも、長期間に亘ってウォッシュコート層の破壊、脱落を避けることができるものである。また、本発明は、基本製造プロセスとして工業的にもっとも安価に製造できる中和沈殿法を採用しており、排水に硝酸イオンが含まれず、低コストでセリア−ジルコニア系複合酸化物を提供することができ、日本国内で約４０００万個/年使用されているとされている自動車排ガス触媒の経済性の改善に寄与するところ大である。 The ceria-zirconia composite oxide according to the present invention avoids the destruction and dropping of the washcoat layer over a long period of time even when used as a promoter in an automobile exhaust gas purification catalyst used in the vicinity of an engine. It is something that can be done. In addition, the present invention employs a neutralization precipitation method that can be produced industrially at the lowest cost as a basic production process, and provides a ceria-zirconia-based composite oxide that does not contain nitrate ions in the waste water and is low in cost. It contributes to the improvement of the economic efficiency of automobile exhaust catalyst, which is said to be used in Japan at about 40 million pieces / year.
本発明のセリア−ジルコニア系複合酸化物を製造する最も基本的な工程は、塩化セリウム、オキシ塩化ジルコニウムとするセリウム（III）イオン及びジルコニウムイオンを含む酸性溶液を準備する第１段階と、前記酸性溶液にペルオキソ二硫酸塩を添加してセリウム（III）イオンをセリウム（IV）イオンに酸化する第２段階と、前記第２段階で得られたセリウム（IV）イオンと未反応のペルオキソ二硫酸塩を含む溶液を加熱してセリウム（IV）イオン及びジルコニウムイオンを硫酸塩として沈殿させスラリー溶液を得る第３段階と、前記第３段階で得られたスラリー溶液に塩基を添加してセリウム−ジルコニウム系水酸化物スラリーを得る第４段階と、前記セリウム−ジルコニウム系水酸化物スラリーを固液分離後、洗浄、乾燥及び焼成す第５段階とから成り立っている。 The most basic process for producing the ceria-zirconia composite oxide of the present invention includes a first step of preparing an acidic solution containing cerium (III) ions and zirconium ions as cerium chloride and zirconium oxychloride, and the acidic process. A second stage in which peroxodisulfate is added to the solution to oxidize cerium (III) ions to cerium (IV) ions, and peroxodisulfate unreacted with the cerium (IV) ions obtained in the second stage A third step of heating the solution containing cerium (IV) ions and zirconium ions as sulfates to obtain a slurry solution, and adding a base to the slurry solution obtained in the third step to add a cerium-zirconium system A fourth step of obtaining a hydroxide slurry; and a fifth step of washing, drying and calcining the cerium-zirconium hydroxide slurry after solid-liquid separation. It is made up of the floor.
前記第１段階においては、セリウム（III）イオン及びジルコニウムイオンを含む酸性溶液を準備する。セリウム源として塩化セリウム水溶液を使用することができる。ジルコニウム源としてオキシ塩化ジルコニウム水溶液を使用することができる。これらの量比は製品セリア−ジルコニア複合酸化物中のセリア／ジルコニア比が所望の値になるように調整すればよい。原料には硝酸塩など他の原料を使用することもできるが、排水中に含まれる硝酸イオンを処理する特別な工程が必要となり、経済的に不利であるため硝酸塩の使用は避けるべきである。 In the first step, an acidic solution containing cerium (III) ions and zirconium ions is prepared. An aqueous cerium chloride solution can be used as the cerium source. An aqueous zirconium oxychloride solution can be used as the zirconium source. These quantity ratios may be adjusted so that the ceria / zirconia ratio in the product ceria-zirconia composite oxide becomes a desired value. Although the raw material can also be used other materials such as nitrates, special treating the nitrate ions contained in the wastewater is required, the use of nitrate salts for is economically disadvantageous should be avoided.
上記セリウム（III）イオン及びジルコニウムイオンを含む酸性溶液は、ｐＨ１以下、かつその濃度が酸化物換算の合計量で１０〜２００ｇ／ｌ（リットル）に調整するのが望ましい。１０g／ｌ未満の濃度では得られる複合水酸化物量が少な過ぎて生産効率が悪く、２００ｇ／ｌを超える濃度では、反応によって生ずるスラリーの粘度が高くなりすぎ十分な混合状態が得られなくなるので好ましくない。 The acidic solution containing cerium (III) ions and zirconium ions is preferably adjusted to a pH of 1 or less and a concentration of 10 to 200 g / l (liter) in terms of the total amount in terms of oxides. If the concentration is less than 10 g / l, the amount of the composite hydroxide obtained is too small and the production efficiency is poor. If the concentration exceeds 200 g / l, the viscosity of the slurry produced by the reaction becomes too high, and a sufficient mixed state cannot be obtained. Absent.
第２段階では、前記第１段階で得られた酸性溶液に酸化剤として作用するペルオキソ二硫酸塩を添加してセリウム（III）イオンをセリウム（IV）イオンに酸化する。ペルオキソ二硫酸塩は、セリウム（III）をセリウム（IV）イオンに酸化するとともに酸化反応によって生成した硫酸イオンがセリウム（IV）イオン、ジルコニウムイオンを硫酸塩として沈殿させるのに十分な量となるように添加する。 In the second stage, peroxodisulfate that acts as an oxidizing agent is added to the acidic solution obtained in the first stage to oxidize cerium (III) ions to cerium (IV) ions. Peroxodisulfate is sufficient to oxidize cerium (III) to cerium (IV) ions, and the sulfate ions produced by the oxidation reaction are sufficient to precipitate cerium (IV) ions and zirconium ions as sulfate. Add to.
上記III価セリウムイオンをセリウム（IV）イオンにするのに必要なペルオキソ二硫酸塩の必要量は以下の(２)式から算出することができ、セリウム（III）イオンの１モルに対してペルオキソ二硫酸イオン０．５モル相当を添加すれば、セリウム（III）イオンをセリウム（IV）イオンに酸化できるとともに、生成したセリウム（IV）イオンをその硫酸塩とすることができる。２Ｃｅ３＋＋Ｓ２Ｏ８ ２−→２Ｃｅ４＋＋２ＳＯ４ ２−・・・（２）
一方、ジルコニウムイオンをその硫酸塩とするためには、塩基性硫酸塩（Ｚｒ（ＯＨ）（４−２Ｘ）ＳＯ４・ｎＨ２Ｏを形成することを考慮して、ジルコニウムイオンの１モルに対してペルオキソ二硫酸イオン０．２５モル相当を添加すればよい。ただし、ペルオキソ二硫酸イオンの硫酸イオンへの分解効率を考慮してその分過剰に添加することが考慮されるべきである。
The necessary amount of peroxodisulfate necessary for converting the above-mentioned III-valent cerium ion to cerium (IV) ion can be calculated from the following formula (2), and peroxo per mol of cerium (III) ion: When 0.5 mol equivalent of disulfate ion is added, cerium (III) ion can be oxidized to cerium (IV) ion, and the generated cerium (IV) ion can be converted to its sulfate. 2Ce 3+ + S 2 O 8 2− → 2Ce 4+ + 2SO 4 2− (2)
On the other hand, in order to convert zirconium ion to its sulfate, in consideration of forming basic sulfate (Zr (OH) (4-2X) SO 4 .nH 2 O, 1 mol of zirconium ion In this case, 0.25 mol of peroxodisulfate ion may be added, but it should be considered that excessive addition is made considering the decomposition efficiency of peroxodisulfate ion into sulfate ion.
ペルオキソ二硫酸塩としてはペルオキソ二硫酸ナトリウム、ペルオキソ二硫酸カリウム、ペルオキソ二硫酸アンモニウムなど通常工業的に利用できるペルオキソ二硫酸塩をすべて使用できる。 As the peroxodisulfate, all peroxodisulfates that are usually industrially available such as sodium peroxodisulfate, potassium peroxodisulfate, and ammonium peroxodisulfate can be used.
第３段階では、上記第２段階で未反応の状態で残ったペルオキソ二硫酸塩とセリウム（IV）イオンを含む溶液を加温してセリウム及びジルコニウムの硫酸塩を含むスラリー溶液を得る。加温は５０℃以上とすることが好ましい。加温が５０℃未満であると、ペルオキソ二硫酸イオンの硫酸イオンへの分解速度（硫酸イオンの生成速度）が小さく工業的に不利となるからである。加温手段については特に制限はなく、また、加温中にたとえば撹拌羽根、ポンプ循環などを用いて撹拌することも行うことができる。この加温を伴う第３段階において、セリウム（IV）イオン及びジルコニウム（IV）イオンはともにほぼ同時に硫酸塩として沈降し、混合状態のよいスラリー溶液が得られる。 In the third stage, the solution containing the peroxodisulfate and cerium (IV) ions remaining unreacted in the second stage is heated to obtain a slurry solution containing cerium and zirconium sulfate. The heating is preferably 50 ° C. or higher. This is because if the heating is less than 50 ° C., the decomposition rate of peroxodisulfate ions into sulfate ions (rate of formation of sulfate ions) is small and industrially disadvantageous. There is no particular limitation on the heating means, and stirring can be performed using, for example, a stirring blade or a pump circulation during heating. Oite the third stage with this warming, precipitated as cerium (IV) ions and zirconium (IV) ions are both substantially simultaneously sulfate, good slurry solution is obtained the mixed state.
前記第３段階で得たセリウム（IV）イオン及びジルコニウム（IV）イオンの硫酸塩を含むスラリー溶液には、塩基を添加してセリウム−ジルコニウム系水酸化物スラリーを得る（第４段階）。この第４段階は、アルカリを添加する中和工程であり、これによりセリウム（IV）イオン及びジルコニウム（IV）イオンの水酸化物スラリーを得ることができる。第３段階で得られた硫酸塩はｐＨ８以上でその大部分の硫酸イオンが水酸化物イオン（ＯＨ−）に置換され水酸化物となるので中和操作はｐＨを８以上にするように行えばよい。アルカリとしては工業的に通常使用されるアルカリ、例えば水酸化ナトリウム、水酸化カリウム、アンモニア水などを使用できる。中和による硫酸イオンの水酸化物イオンへの置換を完全に行うために、撹拌羽根による撹拌やポンプによる循環など、工業的通常に行われる撹拌操作をあわせて行うことが望ましい。 A base is added to the slurry solution containing sulfate of cerium (IV) ions and zirconium (IV) ions obtained in the third step to obtain a cerium-zirconium hydroxide slurry (fourth step). This fourth stage is a neutralization step in which an alkali is added, whereby a hydroxide slurry of cerium (IV) ions and zirconium (IV) ions can be obtained. The sulfate obtained in the third stage is pH 8 or higher, and most of the sulfate ions are replaced with hydroxide ions (OH − ) to form hydroxides. Just do it. As the alkali, industrially commonly used alkali such as sodium hydroxide, potassium hydroxide, aqueous ammonia and the like can be used. In order to completely replace sulfate ions with hydroxide ions by neutralization, it is desirable to carry out industrially common stirring operations such as stirring with stirring blades and circulation with a pump.
上記第４段階に続いてセリウム−ジルコニウム系水酸化物スラリーを固液分離操作、洗浄操作、及び乾燥及び焼成操作を含む第５段階の処理が行われる。固液分離操作の手段は特に問わず、遠心分離装置、ろ過装置など工業的に使用される装置を使用することができる。洗浄操作は、セリウム−ジルコニウム系水酸化物スラリーから硫酸イオン、塩化物イオンなど夾雑イオンの低減を行うための操作であって、たとえば純水中に水酸化物を分散させた後、遠心分離装置、ろ過装置を用いて行う。この洗浄操作は水酸化物中の夾雑イオンの含有量が質量比で３％以下になるまで続けることが望ましい。 Subsequent to the fourth stage, a cerium-zirconium hydroxide slurry is subjected to a fifth stage process including a solid-liquid separation operation, a washing operation, and a drying and firing operation. The means for the solid-liquid separation operation is not particularly limited, and industrially used devices such as a centrifugal separator and a filtration device can be used. The washing operation is an operation for reducing impurities such as sulfate ions and chloride ions from the cerium-zirconium hydroxide slurry. For example, after dispersing the hydroxide in pure water, the centrifugal separator , Using a filtration device. This washing operation is preferably continued until the content of impurities in the hydroxide becomes 3% or less by mass ratio.
上記により得られたセリウム−ジルコニウム系水酸化物には乾燥及び焼成操作が行われる。乾燥操作は工業的に使用される外熱式または内燃式乾燥装置を使用して乾燥温度６０〜２００℃程度で行い、これにより水酸化物に対する付着水分量を質量比で４０〜９０％程度から１０％以下に低減する。 The cerium-zirconium hydroxide obtained as described above is dried and fired. The drying operation is carried out at a drying temperature of about 60 to 200 ° C. using an industrially used external heat type or internal combustion type drying device, and thereby the amount of moisture adhering to the hydroxide is from about 40 to 90% by mass ratio. Reduce to 10% or less.
乾燥操作に続いて焼成操作が行われる。焼成温度は用途に応じて適当に選ぶことができるが、実用的には１０００℃以下とするのがよい。なお、上記乾燥操作と焼成操作はそれぞれ独立した操作として行うこともできるが、一連の連続操作して行うこともできる。また、乾燥操作後最終焼成に先立って４００〜８００℃程度の温度で仮焼を行うこともでき、仮焼に先立って、あるいは仮焼後に水酸化物の破砕を行うこともできる。 A baking operation is performed following the drying operation. The firing temperature can be appropriately selected according to the use, but it is preferable to set it to 1000 ° C. or less practically. In addition, although the said drying operation and baking operation can also be performed as each independent operation, it can also be performed by a series of continuous operation. In addition, calcination can be performed at a temperature of about 400 to 800 ° C. prior to final firing after the drying operation, and hydroxide can be crushed prior to or after calcination.
上記焼成によってセリウム−ジルコニウム系水酸化物は脱水され、これらの複合酸化物となる。このようにして得られたセリア−ジルコニア系複合酸化物は、必要に応じて粉砕を行い粒度の調整を行う。粉砕は、所望の粒度に調整できればよく、スタンプミル、ローラーミル、ジェットミルまたはボールミルなど、工業的に使用されるミルを用いて行うことができる。 By the firing, the cerium-zirconium hydroxide is dehydrated and becomes a composite oxide thereof. The ceria-zirconia composite oxide thus obtained is pulverized as necessary to adjust the particle size. The pulverization only needs to be able to be adjusted to a desired particle size, and can be performed using an industrially used mill such as a stamp mill, a roller mill, a jet mill, or a ball mill.
上記一連の段階からなる工程によって得られたセリア−ジルコニア系複合酸化物は、後述の実施例に示すように、１２００℃で１２時間焼成後の一次粒子径が２００ｎｍ以下であるという特徴を有する。また、１２００℃で１２時間焼成後の一次粒子径が１０００℃で１２時間焼成後の一次粒子径の３倍以下であるという特徴を有する。 The ceria-zirconia composite oxide obtained by the process consisting of a series of steps described above has a feature that the primary particle diameter after firing at 1200 ° C. for 12 hours is 200 nm or less, as shown in the examples described later. In addition, the primary particle size after firing at 1200 ° C. for 12 hours is not more than 3 times the primary particle size after firing at 1000 ° C. for 12 hours.
本発明により得られたセリア−ジルコニア系複合酸化物が１２００℃焼成後において一次粒子が成長しない理由は、必ずしも確定的ではないが、一般的な硝酸塩中和法では硝酸塩から直接、水酸化物が生成するのに対して、本発明では酸性溶液中で一旦硫酸イオンを核とした硫酸塩の沈殿が形成された後、該硫酸塩の硫酸イオンを水酸化物イオンに置換する形で水酸化物が生成されることに起因すると推定される。 The reason why the primary particles do not grow after the ceria-zirconia composite oxide obtained by the present invention after firing at 1200 ° C. is not necessarily definite, but in a general nitrate neutralization method, the hydroxide is directly generated from the nitrate. In contrast, in the present invention, a sulfate precipitate having a sulfate ion as a nucleus is once formed in an acidic solution, and then the sulfate ion of the sulfate is replaced with a hydroxide ion. Is presumed to be caused by
すなわち、従来の硝酸塩中和法では、セリウムとジルコニウムでは沈殿を生成するｐＨが異なるため、これら水酸化物の原子レベルでの混合が達成され難く、また不定形の水酸化物が形成される。そのため、水酸化物生成時のセリウムイオンとジルコニウムイオンの位置が、構成元素が規則的な繰り返し構造を取るセリア−ジルコニア酸化物結晶と大きくずれることになる。このような水酸化物は、加熱により酸化物結晶となる際及びその後の加熱・焼成に当たり、構成原子がセリア-ジルコニア酸化物結晶として取るべき位置まで大きく移動する必要があり、それに伴い粒子成長が著しく進行することになる。 That is, in the conventional nitrate neutralization method, cerium and zirconium have different pHs at which precipitates are formed. Therefore, it is difficult to achieve mixing at the atomic level of these hydroxides, and amorphous hydroxides are formed. Therefore, the positions of cerium ions and zirconium ions at the time of hydroxide generation are greatly shifted from the ceria-zirconia oxide crystal in which the constituent elements have a regular repeating structure. When such a hydroxide is converted into an oxide crystal by heating, and during subsequent heating and firing, it is necessary for the constituent atoms to move greatly to a position to be taken as a ceria-zirconia oxide crystal, and as a result, particle growth occurs. It will progress significantly.
これに対し、本発明においては、酸性溶液中で一旦硫酸イオンを核とした硫酸塩の沈殿が形成された後、該硫酸塩の硫酸イオンを水酸化物イオンに置換する形で水酸化物が生成される。硫酸イオンを核とする硫酸塩はイオン性結晶であり、強いクーロン力により結び付けられているため最密充填構造を取りやすい。この結果、構成元素が最終的目的物であるセリア−ジルコニア酸化物結晶に近似し、かつこれと整合性のある規則的な繰り返し構造を取ることになる。本発明では、このような構造の硫酸塩を形成した後に、硫酸イオンを水酸化物イオンで置換されるので、セリア−ジルコニア酸化物結晶に近似した構造を有する水酸化物が得られ、加熱により脱水された複合酸化物は構成元素が規則的な繰り返し構造を取るものとなり、その後の高温、例えば１２００℃への加熱によっても原子の移動が起きにくく結果として粒子成長が起こりにくくなったと推定される。 On the other hand, in the present invention, a sulfate precipitate having a sulfate ion as a nucleus is once formed in an acidic solution, and then the hydroxide is replaced in the form of replacing the sulfate ion of the sulfate with a hydroxide ion. Generated. Sulfates with sulfate ions as nuclei are ionic crystals and are linked by strong Coulomb force, so that they can easily have a close-packed structure. As a result, the constituent elements have a regular repetitive structure that approximates and is consistent with the ceria-zirconia oxide crystal that is the final target. In the present invention, after the sulfate having such a structure is formed, the sulfate ion is substituted with the hydroxide ion, so that a hydroxide having a structure similar to a ceria-zirconia oxide crystal is obtained and heated. The dehydrated composite oxide has a structure in which the constituent elements have a regular repeating structure, and it is estimated that even when heated to a high temperature thereafter, for example, 1200 ° C., it is difficult for atoms to move and as a result, particle growth is less likely to occur. .
以上、本発明の基本的な構成について説明したが、本発明は下記のような実施形態を取ることができる。 Although the basic configuration of the present invention has been described above, the present invention can take the following embodiments.
まず、セリウム(III)イオンをセリウム（IV）イオンに酸化する第２段階において、ペルオキソ二硫酸塩とともに硫酸塩を添加することができる。この場合においては、酸性溶液に対するペルオキソ二硫酸塩の添加量をセリウム(III)イオンをセリウム（IVイオンに酸化するに必要な程度あるいはそれよりやや過剰な程度に留め、ジルコニウム（IV）イオンを硫酸塩として沈殿させるに必要な硫酸イオンはその一部又は全部を別途添加する硫酸塩に置換するのである。なお、上記硫酸イオンは、酸化されたセリウム（IV）イオン及びジルコニウム（IV）イオンを硫酸塩として沈殿させる第３段階において添加するようにしてもよい。 First, in the second stage of oxidizing cerium (III) ions to cerium (IV) ions, sulfate can be added along with peroxodisulfate. In this case, the amount of peroxodisulfate added to the acidic solution is limited to a level necessary for oxidizing cerium (III) ions to cerium (or to a level slightly higher than that of IV ions, and zirconium (IV) ions to sulfuric acid. The sulfate ion necessary for precipitation as a salt is replaced by a sulfate salt that is added separately or partially.The sulfate ion converts oxidized cerium (IV) ion and zirconium (IV) ion to sulfate. You may make it add in the 3rd step which precipitates as a salt.
硫酸イオン源としては硫酸ナトリウム、硫酸カリウム、硫酸アンモニウムなど通常工業的に利用できる水溶性の硫酸塩をすべて使用できる。その添加量はセリウム、ジルコニウムの合算１モルに対して追加硫酸イオンとペルオキソ二硫酸塩が分解して生成する硫酸イオンをあわせて０.３モル以上、好ましくは０．４モル以上とすることが望ましい。 As the sulfate ion source, all water-soluble sulfates that are usually industrially available such as sodium sulfate, potassium sulfate, and ammonium sulfate can be used. The added amount is 0.3 mol or more, preferably 0.4 mol or more in total of sulfate ions formed by decomposition of additional sulfate ions and peroxodisulfate with respect to 1 mol of cerium and zirconium combined. desirable.
また、セリウム(III)イオンをセリウム（IV）イオンに酸化する第２段階において、ペルオキソ二硫酸塩の全部又は一部を過酸化水素に代替するとともに、該第２段階又は後続の第３段階においてセリウム（IV）イオン及びジルコニウムイオンの全てを硫酸塩として沈殿させるに必要な硫酸塩を添加することもできる。この場合における酸化反応は
２Ｃｅ３＋＋Ｈ２Ｏ２＋２Ｈ ＋ →２Ｃｅ４＋＋２Ｈ２Ｏ・・・（３）
となる。ただし、この実施形態においては、セリウム（IV）イオン及びジルコニウム（IV）イオンを硫酸塩として沈殿させるための硫酸イオンが不足するので、その分を別途添加しなければならないが、その添加は、前記第２段階（酸化段階）でもよく、あるいは第３段階（沈殿物生成段階）でもよい。
In the second step of oxidizing cerium (III) ions to cerium (IV) ions, all or part of the peroxodisulfate is replaced with hydrogen peroxide, and in the second step or the subsequent third step. Sulfate necessary for precipitating all of the cerium (IV) ions and zirconium ions as sulfate can also be added. The oxidation reaction in this case is 2Ce 3+ + H 2 O 2 + 2H + → 2Ce 4+ + 2H 2 O (3)
It becomes. However, in this embodiment, since there is a shortage of sulfate ions for precipitating cerium (IV) ions and zirconium (IV) ions as sulfates, the amount must be added separately. It may be the second stage (oxidation stage) or the third stage (precipitate formation stage).
本発明においても、セリア−ジルコニア系複合酸化物には、アルミニウム、スカンジウム、イットリウム及び原子番号５７〜７１までの希土類元素（プロメチウムを除く）から選択され、安定な酸化物を形成するときの酸化数が３となる１種又は２種以上の元素からなる第三成分を含有させることができる。これらの元素を添加することによりセリウムが結晶内においてIII価で安定して存在しやすくなりＯＳＣ能、応答速度が向上する。添加量は用途に応じて定めることが好ましく、一般的にその含有量は酸化物に換算した総量に対して質量比で５０％以下とすることが好ましい。第三成分の含有量が５０％を超えると、基本成分であるセリウム含有量が相対的に低下して助触媒として必要なＯＳＣが低くなるため好ましくない。 Also in the present invention, the ceria-zirconia composite oxide is selected from aluminum, scandium, yttrium, and rare earth elements having atomic numbers of 57 to 71 (excluding promethium), and the oxidation number when forming a stable oxide. A third component composed of one or two or more elements in which is 3 can be contained. By adding these elements, cerium tends to be stably present in the crystal in the III state, and the OSC ability and response speed are improved. The addition amount is preferably determined according to the use, and generally the content is preferably 50% or less by mass ratio with respect to the total amount converted to oxide. When the content of the third component exceeds 50%, the content of cerium, which is the basic component, is relatively lowered, and the OSC necessary as a co-catalyst is decreased, which is not preferable.
上記第三成分の添加は、前記第１段階で調整する酸性溶液中に第三成分元素を含有する塩を添加することによって行うことができる。また、第４段階に先立って、若しくは第４段階の際に、あるいはその後に適当な化合物、例えば塩化アルミニウム等を水溶液の形で加えることにより行うこともできる。 The third component can be added by adding a salt containing the third component element to the acidic solution prepared in the first step. It can also be carried out by adding an appropriate compound such as aluminum chloride in the form of an aqueous solution prior to, during or after the fourth stage.
なお、本発明に係るセリア−ジルコニア系複合酸化物の基本組成はセリウムとジルコニウムの配合比率が二酸化セリウム（セリア、Ｃｅ０２）及び酸化ジルコニウム（ジルコニア、ＺｒＯ２）に換算して質量比で１０：９０〜９０：１０とするのがよい。二酸化セリウムの質量比が９０を超えると耐熱性が低下するため所望の性能が得られず、一方、酸化ジルコニウムの質量比が９０を超えるとＯＳＣが低下する。上記質量比を２５:７５〜７５:２５とすればより耐熱性が高い複合酸化物が得られる。 Incidentally, ceria according to the present invention - The basic composition of cerium and zirconium blending ratio cerium dioxide in the zirconia composite oxide (ceria, CeO 2) and zirconium oxide (zirconia, ZrO 2) in a weight ratio in terms of 10: It is good to set it as 90-90: 10. When the mass ratio of cerium dioxide exceeds 90, the heat resistance is lowered, so that desired performance cannot be obtained. On the other hand, when the mass ratio of zirconium oxide exceeds 90, OSC is lowered. When the mass ratio is 25:75 to 75:25, a composite oxide having higher heat resistance can be obtained.
（実施例１）
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液とジルコニア換算濃度２００ｇ／ｌのオキシ塩化ジルコニウム溶液と純水を混合し、合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２＝５０：５０の溶液１ｌ（リットル）を得た（第１段階）。得られた混合溶液にペルオキソ二硫酸アンモニウムを４０ｇ添加し（第２段階）、撹拌しながら９５℃まで加熱し、セリウム-ジルコニウム複合硫酸塩を得た(第３段階)。得られた硫酸塩スラリーを６０℃まで冷却後、アンモニア水を加えて中和し水酸化物を含むスラリーを得た。得られた水酸化物スラリーに対してろ過−洗浄操作を４回繰り返してセリウム-ジルコニウム複合水酸化物ケーキを得た(第４段階)。得られた複合水酸化物ケーキを１２０℃で乾燥して複合水酸化物粉末を得、これをルツボに詰め電気炉で７００℃にて３時間焼成した後、ジェットミルで粉砕してセリア−ジルコニア系複合酸化物粉末(製品)とした（第５段階）。
Example 1
A cerium chloride solution having a cerium dioxide equivalent concentration of 200 g / l, a zirconium oxychloride solution having a zirconia equivalent concentration of 200 g / l and pure water are mixed, and a total oxide equivalent concentration of 50 g / l, CeO 2 : ZrO 2 = 50: 50 solution. 1 l was obtained (first stage). 40 g of ammonium peroxodisulfate was added to the obtained mixed solution (second stage) and heated to 95 ° C. with stirring to obtain a cerium-zirconium composite sulfate (third stage). The obtained sulfate slurry was cooled to 60 ° C. and neutralized by adding ammonia water to obtain a slurry containing hydroxide. Resulting filter against hydroxide slurry - cerium repeated four times washing operations - was obtained zirconium complex hydroxide cake (fourth stage). The obtained composite hydroxide cake was dried at 120 ° C. to obtain a composite hydroxide powder, which was packed in a crucible and fired at 700 ° C. for 3 hours in an electric furnace, and then pulverized with a jet mill to ceria-zirconia. System composite oxide powder (product) (fifth stage).
得られたセリア−ジルコニア系複合酸化物粉末に対して、１０００℃、１１００℃、１２００℃で１２時間仮焼してＢＥＴ３点法によりＢＥＴ比表面積を測定し、（１）式に基づいて一次粒径を求めた。得られたセリア−ジルコニア系複合酸化物の組成分析値は表１に、密度及び仮焼後の比表面積は表２に、同じく仮焼後の一次粒径は表３に、他の実施例等とともにまとめて示した。なお、粒子密度にはＣｅＯ２、ＺｒＯ２にはそれぞれ文献値である７．３、５．５を、その他第三成分元素の酸化物は影響が小さいのですべて７．３と近似して計算した。また、図１には、上記各温度で仮焼後の仮焼温度と一次粒子径との関係を示した。 The obtained ceria-zirconia composite oxide powder was calcined at 1000 ° C., 1100 ° C., 1200 ° C. for 12 hours, and the BET specific surface area was measured by the BET three-point method. Based on the formula (1), the primary particles The diameter was determined. The composition analysis values of the obtained ceria-zirconia composite oxide are shown in Table 1, the density and specific surface area after calcination are shown in Table 2, the primary particle size after calcination is shown in Table 3, and other examples, etc. Together with it. In addition, CeO 2 and ZrO 2 for the particle density were calculated to be 7.3 and 5.5, which are literature values, respectively, and other ternary element oxides had little influence, so all were approximated to 7.3. . FIG. 1 shows the relationship between the calcining temperature after calcining and the primary particle size at each of the above temperatures.
（実施例２）
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液とジルコニア換算濃度２００ｇ／ｌのオキシ塩化ジルコニウム溶液とを純水に溶解し、合計酸化物換算濃度１００ｇ／ｌ、ＣｅＯ２：ＺｒＯ２＝２０：８０の溶液１ｌ（リットル）を得た(第１段階)。得られた混合溶液にペルオキソ二硫酸アンモニウムを３２ｇ、硫酸アンモニウムを８４ｇ添加した後(第２段階)、撹拌しながら９５℃まで加熱し、セリウム−ジルコニウム複合硫酸塩を得た(第３段階)。以下、実施例１と同様に処理して複合水酸化物粉末を得(第４段階)、さらに仮焼してセリア−ジルコニア複合酸化物を得た(第５段階)。
(Example 2)
A cerium chloride solution having a cerium dioxide equivalent concentration of 200 g / l and a zirconium oxychloride solution having a zirconia equivalent concentration of 200 g / l are dissolved in pure water, and the total oxide equivalent concentration is 100 g / l, CeO 2 : ZrO 2 = 20: 80. 1 l (liter) of solution was obtained (first stage). After adding 32 g of ammonium peroxodisulfate and 84 g of ammonium sulfate to the obtained mixed solution (second stage), the mixture was heated to 95 ° C. with stirring to obtain a cerium-zirconium composite sulfate (third stage). Thereafter, a composite hydroxide powder was obtained in the same manner as in Example 1 (fourth stage), and further calcined to obtain a ceria-zirconia composite oxide (fifth stage).
(実施例３)
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液とジルコニア換算濃度２００ｇ／ｌのオキシ塩化ジルコニウム溶液と純水を混合し、合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２＝４０：６０の溶液１ｌ（リットル）を得た（第１段階）。得られた混合溶液に３１％の過酸化水素水を３０ｇ、硫酸アンモニウムを６０ｇ添加した後(第２段階)、撹拌しながら９５℃まで加熱し、セリウム-ジルコニウム複合硫酸塩を得た(第３段階)。以下、実施例１と同様に処理して複合水酸化物粉末を得(第４段階)、さらに仮焼してセリア−ジルコニア系複合酸化物を得た(第５段階)。
Example 3
A cerium chloride solution having a cerium dioxide equivalent concentration of 200 g / l, a zirconia equivalent concentration of 200 g / l zirconium oxychloride solution and pure water are mixed, and a total oxide equivalent concentration of 50 g / l, CeO 2 : ZrO 2 = 40: 60 solution. 1 l was obtained (first stage). After adding 30 g of 31% hydrogen peroxide and 60 g of ammonium sulfate to the obtained mixed solution (second stage), the mixture was heated to 95 ° C. with stirring to obtain a cerium-zirconium composite sulfate (third stage). ). Thereafter, a composite hydroxide powder was obtained in the same manner as in Example 1 (fourth stage), and further calcined to obtain a ceria-zirconia composite oxide (fifth stage).
(実施例４)
二酸化セリウム換算濃度２００g／ｌの塩化セリウム溶液とジルコニア換算濃度２００ｇ／ｌのオキシ塩化ジルコニウム溶液と純水を混合し、合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２＝７０：３０の溶液１ｌ（リットル）を得た（第１段階）。得られた混合溶液に３１％過酸化水素水を３０ｇ、ペルオキソ二硫酸アンモニウムを５５ｇ添加した後（第２段階）、撹拌しながら９０℃まで加熱し、セリウム−ジルコニウム複合硫酸塩を得た（第３段階）。以下、実施例１と同様に処理して複合水酸化物粉末を得（第４段階）、さらに仮焼してセリア-ジルコニア複合酸化物を得た（第５段階）。
Example 4
A cerium chloride solution having a cerium dioxide equivalent concentration of 200 g / l, a zirconium oxychloride solution having a zirconia equivalent concentration of 200 g / l, and pure water are mixed, and a total oxide equivalent concentration of 50 g / l, CeO 2 : ZrO 2 = 70: 30 1 l was obtained (first stage). After adding 30 g of 31% hydrogen peroxide and 55 g of ammonium peroxodisulfate to the obtained mixed solution (second stage), the mixture was heated to 90 ° C. with stirring to obtain a cerium-zirconium composite sulfate (third). Stage). Thereafter, a composite hydroxide powder was obtained in the same manner as in Example 1 (fourth stage), and further calcined to obtain a ceria-zirconia composite oxide (fifth stage).
(実施例５)
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液１００ｍｌとジルコニア換算濃度２００ｇ／ｌのオキシ塩化ジルコニウム溶液１２５ｍｌとを混合した後、酸化ランタン５ｇを加え溶解させた後に純水を加え合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２：Ｌａ２Ｏ３＝４０：５０：１０の溶液１ｌ（リットル）を得た(第１段階)。得られた混合溶液にペルオキソ二硫酸アンモニウムを３２ｇ、硫酸アンモニウム２０ｇを添加した後（第２段階）、撹拌しながら95℃まで加熱し、セリウム-ジルコニウム複合硫酸塩を得た(第３段階)。以下、実施例１と同様に処理して複合水酸化物粉末を得(第４段階)、さらに仮焼してセリア−ジルコニア系複合酸化物を得た(第５段階)。
(Example 5)
After mixing 100 ml of a cerium chloride solution having a cerium dioxide equivalent concentration of 200 g / l and 125 ml of a zirconium oxychloride solution having a zirconia equivalent concentration of 200 g / l, 5 g of lanthanum oxide was added and dissolved, and then pure water was added to give a total oxide equivalent concentration of 50 g. / L, CeO 2 : ZrO 2 : La 2 O 3 = 40: 50: 10 1 l (liter) was obtained (first stage). After adding 32 g of ammonium peroxodisulfate and 20 g of ammonium sulfate to the obtained mixed solution (second stage), the mixture was heated to 95 ° C. with stirring to obtain a cerium-zirconium composite sulfate (third stage). Thereafter, a composite hydroxide powder was obtained in the same manner as in Example 1 (fourth stage), and further calcined to obtain a ceria-zirconia composite oxide (fifth stage).
（実施例６）
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液１００ｍｌとジルコニア換算濃度２００ｇ/ｌのオキシ塩化ジルコニウム溶液１００ｍｌとを混合した後、塩化アルミ六水和物７．９ｇ（酸化物換算５ｇ）、酸化イットリウム５ｇを加えて溶解させた後にさらに純水を加え合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２：Ａｌ２Ｏ３:Ｙ２Ｏ３＝４０：４０：１０：１０の溶液１ｌ（リットル）を得た（第１段階）。得られた混合溶液にペルオキソ二硫酸アンモニウムを３２ｇ、硫酸アンモニウムを２０ｇ添加した後(第２段階)、撹拌しながら９５℃まで加熱し、セリウム-ジルコニウム系複合硫酸塩スラリーを得た(第３段階)。以下、実施例１と同様に処理して複合水酸化物粉末を得(第４段階)、さらに仮焼してセリア−ジルコニア系複合酸化物を得た(第５段階)。
(Example 6)
After mixing 100 ml of cerium chloride solution with a cerium dioxide equivalent concentration of 200 g / l and 100 ml of zirconium oxychloride solution with a zirconia equivalent concentration of 200 g / l, 7.9 g of aluminum chloride hexahydrate (5 g of oxide equivalent), 5 g of yttrium oxide After adding and dissolving, pure water was further added to give a total oxide equivalent concentration of 50 g / l, CeO 2 : ZrO 2 : Al 2 O 3 : Y 2 O 3 = 40: 40: 10: 10 1 l (liter) Was obtained (first stage). After adding 32 g of ammonium peroxodisulfate and 20 g of ammonium sulfate to the obtained mixed solution (second stage), the mixture was heated to 95 ° C. with stirring to obtain a cerium-zirconium composite sulfate slurry (third stage). Thereafter, a composite hydroxide powder was obtained in the same manner as in Example 1 (fourth stage), and further calcined to obtain a ceria-zirconia composite oxide (fifth stage).
（実施例７）
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液３００ｍｌとジルコニア換算濃度２００ｇ/ｌのオキシ塩化ジルコニウム溶液１５０ｍｌとを混合した後、酸化ランタン５ｇ、酸化ネオジム５ｇを加え溶解させた後にさらに純水を加えて合計酸化物換算濃度１００ｇ／ｌ、ＣｅＯ２：ＺｒＯ２：Ｌａ２Ｏ３：Ｎｄ２Ｏ３＝６０：３０:５:５の溶液１ｌ（リットル）を得た(第１段階)。得られた混合溶液にペルオキソ二硫酸アンモニウムを９６ｇ、硫酸アンモニウムを３０ｇ添加した後(第２段階)、撹拌しながら９５℃まで加熱し、セリウム−ジルコニウム系複合硫酸塩を得た(第３段階)。以下、実施例１と同様に処理して複合水酸化物粉末を得(第４段階)、さらに仮焼してＺｒ、Ｌａ、Ｎｄを含むセリア−ジルコニア系複合酸化物を得た(第５段階)。
(Example 7)
After mixing 300 ml of cerium chloride solution having a cerium dioxide equivalent concentration of 200 g / l and 150 ml of zirconium oxychloride solution having a zirconia equivalent concentration of 200 g / l, 5 g of lanthanum oxide and 5 g of neodymium oxide were dissolved, and pure water was further added. A solution 1 l (liter) having a total oxide equivalent concentration of 100 g / l, CeO 2 : ZrO 2 : La 2 O 3 : Nd 2 O 3 = 60: 30: 5: 5 was obtained (first stage). After adding 96 g of ammonium peroxodisulfate and 30 g of ammonium sulfate to the obtained mixed solution (second stage), the mixture was heated to 95 ° C. with stirring to obtain a cerium-zirconium-based composite sulfate (third stage). Thereafter, a composite hydroxide powder was obtained by the same treatment as in Example 1 (fourth stage), and further calcined to obtain a ceria-zirconia composite oxide containing Zr, La, and Nd (fifth stage). ).
（比較例１）
二酸化セリウム換算濃度２００ｇ／ｌの硝酸セリウム溶液とジルコニア換算濃度２００ｇ／ｌの硝酸ジルコニウム溶液と純水を混合し、合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２＝５０：５０の溶液１ｌ（リットル）を得た。得られた混合溶液にアンモニア水を加えて中和し水酸化物を含むスラリーを得た。以下、実施例１と同様に処理して複合水酸化物粉末を得、さらに仮焼してセリア−ジルコニア系複合酸化物を得た。
(Comparative Example 1)
A cerium nitrate equivalent concentration 200 g / l cerium nitrate solution, a zirconia equivalent concentration 200 g / l zirconium nitrate solution and pure water are mixed, and the total oxide equivalent concentration 50 g / l, CeO 2 : ZrO 2 = 50: 50 solution 1 l (Liter) was obtained. Ammonia water was added to the obtained mixed solution for neutralization to obtain a slurry containing hydroxide. Thereafter, the same treatment as in Example 1 was performed to obtain a composite hydroxide powder, which was further calcined to obtain a ceria-zirconia composite oxide.
（比較例２）
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液１００ｍｌとジルコニア換算濃度２００ｇ/ｌのオキシ塩化ジルコニウム溶液１２５ｍｌとを混合した後、酸化ランタン５ｇを加え溶解させた後にさらに純水を加え合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２：Ｌａ２Ｏ３＝４０：５０：１０の溶液１ｌ（リットル）を得た。得られた混合溶液を撹拌しながら９５℃まで加熱したが沈殿は得られなかった。この溶液を６０℃まで冷却後、アンモニア水を加えて中和し水酸化物を含むスラリーを得た。以下、実施例１と同様に処理して複合水酸化物粉末を得、さらに仮焼してセリア−ジルコニア系複合酸化物を得た。
(Comparative Example 2)
After mixing 100 ml of cerium chloride solution with a cerium dioxide equivalent concentration of 200 g / l and 125 ml of zirconium oxychloride solution with a zirconia equivalent concentration of 200 g / l, 5 g of lanthanum oxide was added and dissolved, and then pure water was added to obtain a total oxide equivalent concentration. 1 l (liter) of a solution of 50 g / l, CeO 2 : ZrO 2 : La 2 O 3 = 40: 50: 10 was obtained. The resulting mixed solution was heated to 95 ° C. with stirring, but no precipitate was obtained. This solution was cooled to 60 ° C. and then neutralized by adding aqueous ammonia to obtain a slurry containing hydroxide. Thereafter, the same treatment as in Example 1 was performed to obtain a composite hydroxide powder, which was further calcined to obtain a ceria-zirconia composite oxide.
（比較例３）
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液１００ｍｌとジルコニア換算濃度２００ｇ/ｌのオキシ塩化ジルコニウム溶液１２５ｍｌとを混合した後、酸化ランタン５ｇを加え溶解させた後にさらに純水を加え合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２：Ｌａ２Ｏ３＝４０：５０：１０の溶液１ｌ（リットル）を得た。得られた混合溶液に硫酸アンモニウムを６０ｇ添加した後、撹拌しながら９５℃まで加熱し、塩基性硫酸ジルコニウムと推測される沈殿を含むスラリーを得た。このスラリーを６０℃まで冷却後、アンモニア水を加えて中和し水酸化物を含むスラリーを得た。以下、実施例１と同様に処理して複合水酸化物粉末を得、さらに仮焼してセリア−ジルコニア系複合酸化物を得た。
(Comparative Example 3)
After mixing 100 ml of cerium chloride solution with a cerium dioxide equivalent concentration of 200 g / l and 125 ml of zirconium oxychloride solution with a zirconia equivalent concentration of 200 g / l, 5 g of lanthanum oxide was added and dissolved, and then pure water was added to obtain a total oxide equivalent concentration. 1 l (liter) of a solution of 50 g / l, CeO 2 : ZrO 2 : La 2 O 3 = 40: 50: 10 was obtained. After adding 60 g of ammonium sulfate to the obtained mixed solution, the mixture was heated to 95 ° C. with stirring to obtain a slurry containing a presumed basic zirconium sulfate. The slurry was cooled to 60 ° C. and then neutralized by adding ammonia water to obtain a slurry containing hydroxide. Thereafter, the same treatment as in Example 1 was performed to obtain a composite hydroxide powder, which was further calcined to obtain a ceria-zirconia composite oxide.
（比較例４）
二酸化セリウム換算濃度２００ｇ／ｌの塩化セリウム溶液とジルコニア換算濃度２００ｇ／ｌのオキシ塩化ジルコニウム溶液と純水を混合し、合計酸化物換算濃度５０ｇ／ｌ、ＣｅＯ２：ＺｒＯ２＝４０：６０の溶液１ｌ（リットル）を得た。得られた混合溶液に３１％過酸化水素水を３０ｇ添加した後、撹拌しながら９５℃まで加熱した。得られた溶液を６０℃まで冷却後、アンモニア水を加えて中和し水酸化物を含むスラリーを得た。以下、実施例１と同様に処理して複合水酸化物粉末を得、さらに仮焼してセリア−ジルコニア系複合酸化物を得た。
(Comparative Example 4)
A cerium chloride solution having a cerium dioxide equivalent concentration of 200 g / l, a zirconia equivalent concentration of 200 g / l zirconium oxychloride solution and pure water are mixed, and a total oxide equivalent concentration of 50 g / l, CeO 2 : ZrO 2 = 40: 60 solution. 1 l (liter) was obtained. After adding 30 g of 31% hydrogen peroxide solution to the obtained mixed solution, it was heated to 95 ° C. with stirring. The obtained solution was cooled to 60 ° C. and then neutralized by adding aqueous ammonia to obtain a slurry containing hydroxide. Thereafter, the same treatment as in Example 1 was performed to obtain a composite hydroxide powder, which was further calcined to obtain a ceria-zirconia composite oxide.
（ウォッシュコート塗布試験）
実施例１で得られたセリア−ジルコニア複合酸化物と比較例１で得られたセリア−ジルコニア複合酸化物をアルミナと共に３００ｃｐｓｉのセラミックハニカム担体にウォッシュコートした。１２００℃で５％Ｈ２／Ａｒ雰囲気と空気雰囲気（２０％Ｏ２雰囲気）を交互に１時間づつ計５０時間の加速劣化試験を行い室温まで冷却した後、元圧力０.６ＭＰａの圧縮空気を吹き付ける脱離試験を行ったところ実施例１のものは脱離が認められなかったが、比較例１のものは多数の脱離片が観察された。
(Wash coat application test)
The ceria-zirconia composite oxide obtained in Example 1 and the ceria-zirconia composite oxide obtained in Comparative Example 1 were wash-coated onto a 300 cpsi ceramic honeycomb carrier together with alumina. After an accelerated deterioration test of 50 hours in total of 1 hour at 5% H 2 / Ar atmosphere and air atmosphere (20% O 2 atmosphere) at 1200 ° C. and cooling to room temperature, compressed air with an original pressure of 0.6 MPa was applied. When a desorption test was performed, no desorption was observed in Example 1, but a large number of desorption pieces were observed in Comparative Example 1.
上記実施例及び比較例から明らかなように、本発明によるセリア−ジルコニア系複合酸化物は、１２００℃で１２時間焼成後の一次粒子径が２００ｎｍ以下であり、また、１２００℃で１２時間焼成後の一次粒子径が１０００℃で１２時間焼成後の一次粒子径の３倍以下であり、特にエンジン近傍２設置される自動車の排ガス浄化用触媒における助触媒として使用されたときウォッシュコート層の破壊、脱落を防止できるものである。 As is clear from the above Examples and Comparative Examples, the ceria-zirconia composite oxide according to the present invention has a primary particle size of 200 nm or less after firing at 1200 ° C. for 12 hours, and after firing at 1200 ° C. for 12 hours. Destruction of the washcoat layer when used as a co-catalyst in a catalyst for exhaust gas purification of automobiles installed in the vicinity of the engine 2 in particular, the primary particle diameter of which is less than 3 times the primary particle diameter after calcination at 1000 ° C. for 12 hours, It can prevent falling off.
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| EP2692432B1 (en) * | 2011-03-31 | 2019-11-13 | Nissan Motor Co., Ltd. | Exhaust gas purification catalyst, exhaust gas purification monolith catalyst, and process for producing exhaust gas purification catalyst |
| EP2540391A1 (en) | 2011-07-01 | 2013-01-02 | Treibacher Industrie AG | Ceria zirconia alumina composition with enhanced thermal stability |
| EP2893979B1 (en) | 2012-09-10 | 2020-11-25 | Nissan Motor Co., Ltd | Exhaust gas purification catalyst, exhaust gas purification monolith catalyst, and method for producing exhaust gas purification catalyst |
| JP6923289B2 (en) * | 2015-11-02 | 2021-08-18 | 新日本電工株式会社 | Oxygen absorption / release material |
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| JP4053623B2 (en) * | 1996-12-27 | 2008-02-27 | 阿南化成株式会社 | Zirconium-cerium composite oxide and method for producing the same |
| JP3595874B2 (en) * | 1999-03-05 | 2004-12-02 | 第一稀元素化学工業株式会社 | Zirconium-cerium composite oxide and method for producing the same |
| JP4352300B2 (en) * | 2001-08-30 | 2009-10-28 | 株式会社豊田中央研究所 | Composite oxide, method for producing the same, and co-catalyst for exhaust gas purification |
| JP3946982B2 (en) * | 2001-11-01 | 2007-07-18 | ニッケイ・メル株式会社 | Method for producing zirconia-ceria based composite oxide |
| JP4660135B2 (en) * | 2004-07-26 | 2011-03-30 | 第一稀元素化学工業株式会社 | Zirconia-based porous body and method for producing the same |
| JP4972868B2 (en) * | 2005-03-17 | 2012-07-11 | 東ソー株式会社 | Surface-modified ceria / zirconia hydrated oxide, oxide thereof, production method thereof, and use thereof |
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| WO2014196100A1 (en) | 2013-06-04 | 2014-12-11 | 新日本電工株式会社 | Ceria-zirconia mixed oxide and method for producing same |
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