JP4582789B2 - Ceria-zirconia solid solution sol and method for producing the same - Google Patents
Ceria-zirconia solid solution sol and method for producing the same Download PDFInfo
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- 239000006104 solid solution Substances 0.000 title claims description 84
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 title claims description 81
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 239000002245 particle Substances 0.000 claims description 41
- 229910052684 Cerium Inorganic materials 0.000 claims description 39
- 229910052726 zirconium Inorganic materials 0.000 claims description 37
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 30
- 239000002253 acid Substances 0.000 claims description 27
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 26
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 24
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 23
- 229910017604 nitric acid Inorganic materials 0.000 claims description 23
- 239000000243 solution Substances 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 14
- 239000000843 powder Substances 0.000 claims description 12
- 150000003839 salts Chemical class 0.000 claims description 10
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 8
- 239000007864 aqueous solution Substances 0.000 claims description 7
- 238000000975 co-precipitation Methods 0.000 claims description 6
- 239000007800 oxidant agent Substances 0.000 claims description 6
- 238000002296 dynamic light scattering Methods 0.000 claims description 5
- 150000000703 Cerium Chemical class 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 150000003754 zirconium Chemical class 0.000 claims description 4
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 3
- 108090000765 processed proteins & peptides Proteins 0.000 claims 1
- 239000003054 catalyst Substances 0.000 description 24
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 12
- 238000000108 ultra-filtration Methods 0.000 description 11
- 238000002441 X-ray diffraction Methods 0.000 description 10
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 9
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 9
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 9
- 239000000706 filtrate Substances 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 7
- 235000011114 ammonium hydroxide Nutrition 0.000 description 7
- 239000002585 base Substances 0.000 description 7
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical compound Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 description 7
- 238000001035 drying Methods 0.000 description 7
- 238000000746 purification Methods 0.000 description 7
- 239000012266 salt solution Substances 0.000 description 7
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 6
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 6
- 238000010335 hydrothermal treatment Methods 0.000 description 6
- 238000006386 neutralization reaction Methods 0.000 description 6
- CMOAHYOGLLEOGO-UHFFFAOYSA-N oxozirconium;dihydrochloride Chemical compound Cl.Cl.[Zr]=O CMOAHYOGLLEOGO-UHFFFAOYSA-N 0.000 description 6
- 238000001935 peptisation Methods 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 239000011362 coarse particle Substances 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 238000003860 storage Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 235000019270 ammonium chloride Nutrition 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- 229910001854 alkali hydroxide Inorganic materials 0.000 description 3
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 3
- 229910021529 ammonia Inorganic materials 0.000 description 3
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 3
- 235000015165 citric acid Nutrition 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
- LRVUGEZGBKPRRZ-UHFFFAOYSA-L oxygen(2-);zirconium(4+);dichloride Chemical compound [O-2].[Cl-].[Cl-].[Zr+4] LRVUGEZGBKPRRZ-UHFFFAOYSA-L 0.000 description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- -1 that is Chemical compound 0.000 description 3
- 230000008719 thickening Effects 0.000 description 3
- BJEPYKJPYRNKOW-REOHCLBHSA-N (S)-malic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O BJEPYKJPYRNKOW-REOHCLBHSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- PXIPVTKHYLBLMZ-UHFFFAOYSA-N Sodium azide Chemical compound [Na+].[N-]=[N+]=[N-] PXIPVTKHYLBLMZ-UHFFFAOYSA-N 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- BJEPYKJPYRNKOW-UHFFFAOYSA-N alpha-hydroxysuccinic acid Natural products OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 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 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 229910052878 cordierite Inorganic materials 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 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 2
- 238000001914 filtration Methods 0.000 description 2
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 2
- 239000001630 malic acid Substances 0.000 description 2
- 235000011090 malic acid Nutrition 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 238000013112 stability test 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
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 1
- 239000012935 ammoniumperoxodisulfate Substances 0.000 description 1
- 150000001540 azides Chemical class 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 239000003426 co-catalyst Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
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- 238000007865 diluting Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
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- 230000007613 environmental effect Effects 0.000 description 1
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- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 239000004310 lactic acid Substances 0.000 description 1
- 235000014655 lactic acid Nutrition 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- JRKICGRDRMAZLK-UHFFFAOYSA-L persulfate group Chemical group S(=O)(=O)([O-])OOS(=O)(=O)[O-] JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
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- 238000002360 preparation method Methods 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
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- 238000005245 sintering Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
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- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
- DUNKXUFBGCUVQW-UHFFFAOYSA-J zirconium tetrachloride Chemical compound Cl[Zr](Cl)(Cl)Cl DUNKXUFBGCUVQW-UHFFFAOYSA-J 0.000 description 1
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Description
本発明は、自動車排ガス浄化用触媒、殊に排ガス浄化用触媒の助触媒として用いられるセリア−ジルコニア固溶体を得るためのセリア−ジルコニア固溶体ゾル及びその製造方法に関する。 The present invention relates to a ceria-zirconia solid solution sol for obtaining a ceria-zirconia solid solution used as an automobile exhaust gas purification catalyst, in particular as a promoter of an exhaust gas purification catalyst, and a method for producing the same.
近年、世界的な環境保全の高まりから自動車の排ガスに対する規制が益々強化される方向にある。現在、自動車の内燃機関から排出されるガスに含まれる未燃焼のHC（炭化水素）、CO（一酸化炭素）およびNOx（窒素酸化物）の３種の有害物質は、三元触媒と呼ばれるPt／Rh／Pdの貴金属表面上で無害なCO2(二酸化炭素)、H2O(水)、N2(窒素)に変換・浄化されている。この３種の有害物質を全て浄化するためには、HC及びCOを酸化し、NOxを還元するために酸化と還元を同時に行う必要があり、酸素分圧を調整する必要がある。そこで、セリウムはＣｅ＋３とＣｅ＋４の双方をとりうるため、外部の酸素分圧に応じて酸素の吸蔵と放出を行なう特性を有し、白金系の触媒に対する助触媒としてセリア即ち酸化セリウムが多用されている。一般に貴金属や助触媒等の触媒成分は、コージェライト製ハニカム上にスラリーとして流し込まれた後、乾燥、焼成工程を経て自動車排ガス浄化用触媒として使用されている。 In recent years, regulations on automobile exhaust gas have been increasingly tightened due to global environmental protection. Currently, the three types of harmful substances, unburned HC (hydrocarbon), CO (carbon monoxide) and NOx (nitrogen oxide) contained in the gas emitted from the internal combustion engine of automobiles, are called Pt, which is called a three-way catalyst. It is converted and purified to harmless CO 2 (carbon dioxide), H 2 O (water), and N 2 (nitrogen) on the surface of / Rh / Pd noble metals. In order to purify all three types of harmful substances, it is necessary to oxidize HC and CO, and to oxidize and reduce simultaneously to reduce NOx, and it is necessary to adjust the oxygen partial pressure. Therefore, since cerium can take both Ce +3 and Ce +4 , it has the characteristic of occluding and releasing oxygen in accordance with the external oxygen partial pressure, and ceria, that is, cerium oxide, is frequently used as a co-catalyst for platinum-based catalysts. Has been. In general, catalyst components such as precious metals and promoters are used as automobile exhaust gas purification catalysts after being poured as a slurry onto a cordierite honeycomb and then dried and fired.
この自動車排ガス浄化用触媒は、他の化学工業で使用する触媒とは異なりエンジン始動直後の低温時から自動車が定速走行に入った高温時までの幅広い温度領域での機能発現が求められている。しかしながら、助触媒にセリアのみを添加してなる三元触媒では高温下でセリアの凝集・粒成長による比表面積の低下、貴金属のシンタリングが生じ触媒自体の性能が低下することが知られている。そこで、耐熱性の改善方法として１９８８年にセリアとジルコニア即ち酸化ジルコニウムとの固溶体が報告され、現在においてもその改良研究開発が進められている（例えば特許文献１参照）。 Unlike the catalysts used in other chemical industries, this automobile exhaust gas purification catalyst is required to exhibit functions in a wide temperature range from a low temperature immediately after engine startup to a high temperature when the automobile enters constant speed driving. . However, it is known that a three-way catalyst in which only ceria is added to the cocatalyst decreases the specific surface area due to ceria aggregation and grain growth at high temperatures, and sintering of the noble metal results in deterioration of the performance of the catalyst itself. . Therefore, a solid solution of ceria and zirconia, that is, zirconium oxide, was reported in 1988 as a method for improving heat resistance, and improvement research and development of the solid solution is ongoing (see, for example, Patent Document 1).
セリアにジルコニアを固溶させてなるセリア−ジルコニア固溶体粉末の製造方法としては、セリウムおよびジルコニウムの硝酸塩混合溶液中にアンモニア水を添加して共沈させた後、空気中１０００℃程度で焼成する方法が開示されている（例えば、非特許文献１参照）。更には、セリウムおよびジルコニウムの混合塩溶液を酸化雰囲気中で噴霧加熱してセリア−ジルコニア固溶体粉末を得る方法などが知られている（例えば、特許文献２参照）。しかし、これらセリア−ジルコニア固溶体粉末は一次粒子が凝集した二次粒子からなり、粉砕したとしても数ミクロンから数十ミクロンの比較的大きな粒子であり、貴金属等の触媒とは微視的には均一に混合し難い分散性が低いものである。従って、この様な触媒を高温度の排ガスに接触させたとしても浄化効率の低いものとなって、三元触媒の助触媒として適しているとは言い難い。 A method for producing a ceria-zirconia solid solution powder obtained by dissolving zirconia in ceria is a method in which ammonia water is added to a nitrate mixed solution of cerium and zirconium and coprecipitated, followed by firing at about 1000 ° C. in air. (For example, refer nonpatent literature 1). Furthermore, a method of obtaining a ceria-zirconia solid solution powder by spraying and heating a mixed salt solution of cerium and zirconium in an oxidizing atmosphere is known (see, for example, Patent Document 2). However, these ceria-zirconia solid solution powders are composed of secondary particles in which primary particles are aggregated, and even if pulverized, they are relatively large particles of several microns to several tens of microns, and are microscopically uniform with catalysts such as precious metals. It is difficult to be mixed in and low dispersibility. Therefore, even if such a catalyst is brought into contact with high-temperature exhaust gas, the purification efficiency is low, and it is difficult to say that the catalyst is suitable as a three-way catalyst promoter.
一方、セリウムおよびジルコニウムの混合塩水溶液を同時並行的に加水分解することから得られる固溶体微粒子およびその製造方法が開示されている（例えば、特許文献３参照）。この開示された技術によれば複合塩水溶液を１００℃/１６８時間もしくは２４０℃/４８時間での水熱処理を行い、その後、得られたゲル状生成物を遠心分離し、乾燥により分散性に優れた固溶体微粒子が得られることを報告している。当該文献には、水熱処理によって生じた固溶体を分散した状態のまま利用する旨の記載もあるが、このような状態の分散体の粒子径は小さく見積もっても数百ナノメートルであり、助触媒として分散性に優れたものとは言い難い。また、このような高温または長時間の水熱処理条件は工業的に不利であり、量産を踏まえた現実的な反応条件とは言い難い。 On the other hand, solid solution fine particles obtained by simultaneously hydrolyzing a mixed salt aqueous solution of cerium and zirconium and a production method thereof are disclosed (for example, see Patent Document 3). According to this disclosed technique, the composite salt aqueous solution is hydrothermally treated at 100 ° C./168 hours or 240 ° C./48 hours, and then the obtained gel product is centrifuged and dried to have excellent dispersibility. It is reported that solid solution fine particles can be obtained. This document also describes that the solid solution generated by hydrothermal treatment is used in a dispersed state, but the particle size of the dispersion in such a state is several hundred nanometers even if estimated to be small. It is difficult to say that it has excellent dispersibility. In addition, such high-temperature or long-time hydrothermal treatment conditions are industrially disadvantageous and are not practical reaction conditions based on mass production.
以上のことから、容易に且つ経済的に製造でき、触媒上へ担持したときの分散性の優れた助触媒としての機能を発現する固溶体の開発が急務となっている。 In view of the above, there is an urgent need to develop a solid solution that can be easily and economically produced and that exhibits a function as a promoter having excellent dispersibility when supported on the catalyst.
上述したように、現在適用されている自動車排ガス浄化用触媒の課題とするところは、貴金属等の触媒との均一混合性に優れ、高い助触媒機能を有する高分散性のセリア−ジルコニア固溶体を提供する材料開発にある。 As described above, the subject of the currently applied automobile exhaust gas purification catalyst is to provide a highly dispersible ceria-zirconia solid solution that is excellent in uniform mixing with noble metals and other catalysts and has a high promoter function. It is in material development.
これを解決する方法として、本発明者らは公知の手法により得られるセリア−ジルコニア共沈ゲルに一定量の酸を添加した後、熱処理することで極めて安定なセリア−ジルコニア固溶体ゾルが得られることを見出し、係る知見に基づき本発明を完成したものである。
即ち、本発明は動的光散乱法による平均粒子径が５〜１００nmであり、セリウム（ＣｅＯ ２ として）とジルコニウム（ＺｒＯ ２ として）の合量として１質量％時のヘイズ率が１０％以下であるセリア−ジルコニア固溶体ゾルとその製造方法に関する。
As a method for solving this, the present inventors can obtain a very stable ceria-zirconia solid solution sol by adding a certain amount of acid to a ceria-zirconia coprecipitated gel obtained by a known technique and then heat-treating it. And the present invention has been completed based on such findings.
That is, the present invention has an average particle diameter of 5 to 100 nm by a dynamic light scattering method, and a haze ratio at 10% by mass or less as a total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) is 10% or less. The present invention relates to a ceria-zirconia solid solution sol and a manufacturing method thereof.
本発明で得られるセリア−ジルコニア固溶体ゾルは、動的光散乱法による平均粒子径が５〜１００nmであることが最大の特徴である。セリア−ジルコニア固溶体の改善の大きな目的は、粒子径が小さく比表面積の大きな固溶体粉末を得て、分散性をよくすることである。それによって担体上へ小さな粒子が均一に分散担持されることになり、高温でもセリアの凝集抑制が達成され、より浄化効率の高い触媒を得ることができる。よって、本発明のセリア−ジルコニア固溶体ゾルの平均粒子径は５〜１００nmであり、明らかに既存の固溶体粒子に比較して微細な粒子である。 The ceria-zirconia solid solution sol obtained by the present invention is characterized in that the average particle diameter by dynamic light scattering method is 5 to 100 nm. A major purpose of improving the ceria-zirconia solid solution is to obtain a solid solution powder having a small particle diameter and a large specific surface area, thereby improving dispersibility. As a result, small particles are uniformly dispersed and supported on the carrier, and ceria aggregation can be suppressed even at high temperatures, and a catalyst with higher purification efficiency can be obtained. Therefore, the average particle diameter of the ceria-zirconia solid solution sol of the present invention is 5 to 100 nm, which is clearly finer than existing solid solution particles.
このような本発明のセリア−ジルコニア固溶体ゾルを利用して担体に含浸担持させると、高い分散状態のまま担体上に固溶体ゾル粒子が付着することになる。ところで、本発明のセリア−ジルコニア固溶体ゾルは、１００℃程度の乾燥温度で乾燥したもののＸ線回析によれば非常に弱いセリア−ジルコニア固溶体のX線回折線を与える。即ち、ゾル粒子自体は、固溶体であるが結晶が充分に成長していない状態にある。しかし、たとえば３００℃以上、好ましくは５００℃で熱処理するとセリア−ジルコニア固溶体独自の結晶相、即ち回折パターンを示すようになる。 When such a ceria-zirconia solid solution sol of the present invention is impregnated and supported on a support, the solid solution sol particles adhere to the support in a highly dispersed state. By the way, the ceria-zirconia solid solution sol of the present invention gives an X-ray diffraction line of a very weak ceria-zirconia solid solution according to X-ray diffraction of what is dried at a drying temperature of about 100 ° C. That is, the sol particle itself is a solid solution but the crystal is not sufficiently grown. However, for example, when the heat treatment is performed at 300 ° C. or higher, preferably 500 ° C., the crystal phase unique to the ceria-zirconia solid solution, that is, a diffraction pattern is exhibited.
以下本発明のゾルについて詳細に説明する。
本発明のゾルは、後述する動的光散乱法で測定される平均粒子径が５〜１００ｎｍの粒子であり、セリウム（ＣｅＯ ２ として）とジルコニウム（ＺｒＯ ２ として）の合量として１質量％時のヘイズ率が１０％以下であるセリア−ジルコニア固溶体ゾルである。このようなゾルは比表面積が大きく、分散性が良好なことから触媒成分としては非常に好ましいものである。ところが、５ｎｍを下廻る平均粒子径からなる超微細な粒子では粒子の表面積が非常に大きくなり過ぎるために濃度が高い場合はゾルが増粘し易くなり、もはや分散性が改善することによる効果は大きくなく、過剰な分散剤を必要とするなど、必ずしも効果的でない。一方、平均粒子径が１００ｎｍを超える大きな粒子のゾルでは、粒子が安定分散せず重力によって沈殿を生じるため好ましくない。また、このような沈降性の粒子は担体に担持する場合にも分散性の面から不均一になりやすく、所望の担持状態を得ることができない。このようなことから平均粒子径としては５〜１００ｎｍ、好ましくは７〜５０ｎｍ、より好ましくは１０〜３０ｎｍが推奨される。
Hereinafter, the sol of the present invention will be described in detail.
The sol of the present invention is a particle having an average particle diameter of 5 to 100 nm measured by a dynamic light scattering method described later, and the total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) is 1% by mass. Is a ceria-zirconia solid solution sol having a haze ratio of 10% or less . Such a sol is very preferable as a catalyst component because of its large specific surface area and good dispersibility. However, in the case of ultrafine particles having an average particle diameter of less than 5 nm, the surface area of the particles becomes too large, so if the concentration is high, the sol tends to thicken and the effect of improving dispersibility is no longer effective. It is not necessarily effective because it is not large and requires an excessive amount of dispersant. On the other hand, a sol of large particles having an average particle diameter exceeding 100 nm is not preferable because the particles are not stably dispersed and precipitation is caused by gravity. Further, such sedimentation particles tend to be non-uniform from the viewpoint of dispersibility even when supported on a carrier, and a desired supported state cannot be obtained. For this reason, an average particle size of 5 to 100 nm, preferably 7 to 50 nm, more preferably 10 to 30 nm is recommended.
更に、本発明のゾルは、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として１質量％時のヘイズ率が１０％以下であるセリア−ジルコニア固溶体ゾルである。即ち、ヘイズ率とは、ゾル溶液の濁りからゾル粒子の単分散の程度をしめすものであり、平均粒子径が５〜１００ｎｍの範囲内にあってもヘイズ率が１０％を超えると分散性に優れたセリア−ジルコニア固溶体層を担体上に形成することができない。よって、本発明のセリア−ジルコニア固溶体ゾルの１質量％時のヘイズ率に関しては、１０％以下、好ましくは５％以下、より好ましくは３％以下が助触媒機能をより高めることができる。 Furthermore, the sol of the present invention is a ceria-zirconia solid solution sol having a haze ratio of 1% by mass or less as a total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ). That is, the haze ratio indicates the degree of monodispersion of the sol particles from the turbidity of the sol solution. Even if the average particle diameter is within the range of 5 to 100 nm, the dispersibility is increased when the haze ratio exceeds 10%. An excellent ceria-zirconia solid solution layer cannot be formed on the carrier. Therefore, regarding the haze ratio at 1% by mass of the ceria-zirconia solid solution sol of the present invention, the promoter function can be further enhanced by 10% or less, preferably 5% or less, more preferably 3% or less.
次いで、本発明のセリア−ジルコニア固溶体ゾルを構成するセリウムとジルコニウムの固溶組成に関しては、Ce／Zr（モル比）が２０/８０〜９５/５の範囲で作成することができる。通常セリウムとジルコニウムのモル比は用途に応じて変更されるが、本発明のゾルは上記モル比の範囲内であれば問題なく製造することができる。 Next, with respect to the solid solution composition of cerium and zirconium constituting the ceria-zirconia solid solution sol of the present invention, Ce / Zr (molar ratio) can be prepared in the range of 20/80 to 95/5. Normally, the molar ratio of cerium and zirconium is changed according to the application, but the sol of the present invention can be produced without any problem as long as it is within the above molar ratio.
本発明のセリア−ジルコニア固溶体ゾルの解膠剤としては塩酸又は硝酸が好ましく用いることができる。解膠剤の添加量に関しては、ゾルを構成する粒子の大きさにもよるが、ゾル中のＣｅとＺｒのモル数の合計に対して０.２〜２.０（モル比）含有するように添加すればよく、塩酸又は硝酸は単独で用いても良いし、塩酸と硝酸の両方を併用しても良い。工業的な利用を考慮し、固溶体が担持された後に触媒が加熱焼成されることを想定すると、焼成炉等に対する腐食性の低い硝酸で分散されたゾルがより汎用的である。また、本発明のゾルの濃度に関しては、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として１〜３０質量％の範囲内で用いることができ、この範囲内であれば、加熱濃縮や限外ろ過による濃縮により高濃度化しても濃度に応じて粘度が増加するだけで充分安定である。 As the peptizer of the ceria-zirconia solid solution sol of the present invention, hydrochloric acid or nitric acid can be preferably used. The amount of peptizer added depends on the size of the particles that make up the sol, but is 0.2 to 2.0 (molar ratio) with respect to the total number of moles of Ce and Zr in the sol. The hydrochloric acid or nitric acid may be used alone, or both hydrochloric acid and nitric acid may be used in combination. Considering industrial use, assuming that the catalyst is heated and calcined after the solid solution is supported, a sol dispersed with nitric acid having low corrosiveness to a calcining furnace or the like is more general. In addition, regarding the concentration of the sol of the present invention, the total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) can be used within a range of 1 to 30% by mass. Even if the concentration is increased by concentration or concentration by ultrafiltration, the viscosity is increased according to the concentration and is sufficiently stable.
次に本発明のセリア−ジルコニア固溶体ゾルの製造方法について説明する。本発明の固溶体ゾルは、上述したようにその分散しているゾル粒子の平均粒子径が５〜１００ｎｍであり、セリウム（ＣｅＯ ２ として）とジルコニウム（ＺｒＯ ２ として）の合量として１質量％時のヘイズ率が１０％以下であることに特徴を有し、ゲルを特定の酸で解膠してゾル化することに特徴を有する。従って、ゾルの原料となるセリウムとジルコニウムが複合化されたゲルの作成方法そのものについては特段、制限されることなく、公知の方法を用いるができる。本発明で推奨する方法に関して述べれば、水溶性セリウム塩と水溶性ジルコニウム塩との混合塩水溶液を塩基で中和し、セリウムとジルコニウムが共沈したセリアージルコニアゲルを挙げることができる。
Next, the manufacturing method of the ceria-zirconia solid solution sol of this invention is demonstrated. Solid solution sol of the present invention has an average particle diameter of 5~100nm der of Dispersed sol particles as described above is, 1% by mass as the total amount of cerium (as CeO 2) and zirconium (as ZrO 2) It is characterized in that the haze ratio at the time is 10% or less, and it is characterized in that the gel is peptized with a specific acid to form a sol. Therefore, a known method can be used without any particular limitation on the method for producing a gel in which cerium and zirconium as a sol raw material are combined. As for the method recommended in the present invention, a ceria-zirconia gel in which a mixed salt aqueous solution of a water-soluble cerium salt and a water-soluble zirconium salt is neutralized with a base and cerium and zirconium are coprecipitated can be mentioned.
水溶性セリウム塩としては、硝酸セリウム、塩化セリウムなどを例示することができる。また、水溶性ジルコニウム塩としては、硝酸ジルコニウム、塩化ジルコニウムなどを例示することができる。更に本発明で用いる塩基としては、アンモニア、尿素、水酸化アルカリなどを例示することができる。この共沈法によるセリアージルコニアゲルの作成方法は古くから知られており、中和してゲルが生成するときにセリウムとジルコニウムが共存していれば塩基に混合塩水溶液を加えても良いし、混合塩水溶液に塩基を加えても良い。また、中和時の温度や中和の速度を変更することでゲルの性状を変化させることもできるが、いずれの場合でも本発明に使用できるゲルを得ることができる。ところで、このような中和による共沈によりゲルを作成するときには、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として１０質量％以下の濃度で中和することが必要である。１０質量％を超えて中和した場合、後段の酸による解膠時に十分にゲルが解膠しなかったり、多量の酸を必要としたり、また時には数百ナノメートル以上の粗大な粒子が発生することがある。後段の解膠工程を考慮すると、５質量％以下、さらに好ましくは３質量％以下で中和を行うことが好ましい。さて、このようにして共沈させたゲルは通常の乾燥、焼成を施すことで粉体状のセリア−ジルコニア固溶体が得られるが、乾燥、焼成時に平均粒子径が数ミクロン以上の粗大な粒子が生成することで利用上問題があることはいうまでもない。 Examples of the water-soluble cerium salt include cerium nitrate and cerium chloride. Examples of water-soluble zirconium salts include zirconium nitrate and zirconium chloride. Furthermore, examples of the base used in the present invention include ammonia, urea, and alkali hydroxide. The preparation method of ceria-zirconia gel by this coprecipitation method has been known for a long time. If cerium and zirconium coexist when neutralized to form a gel, a mixed salt aqueous solution may be added to the base. A base may be added to the mixed salt aqueous solution. Moreover, although the property of a gel can also be changed by changing the temperature at the time of neutralization and the speed | rate of neutralization, the gel which can be used for this invention can be obtained in any case. By the way, when preparing a gel by such coprecipitation by neutralization, it is necessary to neutralize at a concentration of 10% by mass or less as a total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ). When neutralization exceeds 10% by mass, the gel does not sufficiently pept at the time of subsequent peptization with acid, a large amount of acid is required, and sometimes coarse particles of several hundred nanometers or more are generated. Sometimes. Considering the subsequent peptization step, neutralization is preferably performed at 5% by mass or less, more preferably 3% by mass or less. The gel co-precipitated in this way is usually dried and calcined to obtain a powdery ceria-zirconia solid solution. During drying and calcining, coarse particles having an average particle diameter of several microns or more are obtained. Needless to say, there is a problem in using it.
本発明において重要な点は、共沈させたセリア−ジルコニアゲル中の中和によって生成した副生塩類を洗浄により除去した後、酸で解膠することである。この副生塩類が多く残存すると後段のゾル化が充分進行しないか、所望するゾルを得ることができない。洗浄の目安としては、洗浄液の電気伝導度５０ｍＳ／ｍ以下、好ましくは３０ｍＳ／ｍ以下となるまで洗浄することが重要である。次いで、これをＣｅとＺｒのモル数の合計に対して０.２〜２.０（モル比）の塩酸又は硝酸を添加し加熱処理して解膠する。 The important point in the present invention is that by-product salts formed by neutralization in the co-precipitated ceria-zirconia gel are removed by washing and then peptized with an acid. If a large amount of these by-product salts remain, the subsequent sol formation does not proceed sufficiently, or the desired sol cannot be obtained. As a measure of cleaning, it is important to clean the cleaning liquid until the electric conductivity is 50 mS / m or less, preferably 30 mS / m or less. Subsequently, 0.2 to 2.0 (molar ratio) of hydrochloric acid or nitric acid is added to the total number of moles of Ce and Zr, followed by heat treatment to peptize.
塩酸又は硝酸の添加量が０．２を下廻る場合は本発明の粒子径のゾルは得られず全体が粗大粒子からなるスラリー状を呈したり、部分的に粗大粒子を含んだゾルとなるため好ましくない。また２.０を超えて使用した場合は、もはや酸量を増加させることによる効果がなく、またセリウム及びジルコニウム成分が溶解し、所望する組成比率のセリアージルコニア固溶体が得られない。よって、ゾルの性状や経済性を考慮すると、好ましくはモル比０.３〜１.２の範囲の酸を用いて解膠することが望ましい。一方、塩酸又は硝酸を添加する方法としては特段限定されなく、高濃度の酸溶液をそのままゲルに添加しても良いし、希釈して添加しても良い。またそのときのゲルの濃度も特に制限はなく任意の濃度で酸を添加することができる。 When the addition amount of hydrochloric acid or nitric acid is less than 0.2, the sol having the particle diameter of the present invention cannot be obtained, and the whole forms a slurry form consisting of coarse particles or becomes a sol partially containing coarse particles. It is not preferable. Further, when it is used in excess of 2.0, there is no longer any effect by increasing the acid amount, and the cerium and zirconium components are dissolved and a ceria-zirconia solid solution having a desired composition ratio cannot be obtained. Therefore, considering the properties and economics of the sol, it is desirable to peptize using an acid having a molar ratio in the range of 0.3 to 1.2. On the other hand, the method of adding hydrochloric acid or nitric acid is not particularly limited, and a high-concentration acid solution may be added to the gel as it is, or may be diluted and added. The concentration of the gel at that time is not particularly limited, and the acid can be added at an arbitrary concentration.
ゾル化のための加熱処理条件に関しては、用いる酸の種類や量によって特定できないが、加熱温度５０〜２００℃の範囲で１〜１０時間加熱することで本発明のゾルを得ることができる。具体的に例示すれば、モル比１.０程度の硝酸を用いるときは、９０℃で５時間程度の加熱でゾルを得ることができ、更に水熱条件下１２０℃では３時間程度でゾル化させることができる。 The heat treatment conditions for solification cannot be specified depending on the type and amount of the acid used, but the sol of the present invention can be obtained by heating for 1 to 10 hours at a heating temperature of 50 to 200 ° C. For example, when nitric acid having a molar ratio of about 1.0 is used, a sol can be obtained by heating at 90 ° C. for about 5 hours, and further at about 120 ° C. under hydrothermal conditions for 3 hours. Can be made.
ところで、固溶体組成がセリウムリッチな場合は、ゲルが上記の解膠条件においても、解膠し難く、更に高い温度や長時間の加熱を必要とする場合がある。このような場合は、ゲルに含まれるＣｅ１モルに対して０．２モル以上の酸化剤を添加することで解膠を容易に行うことができる。本発明に用いる酸化剤としては、過酸化水素、オゾン、アジ化ナトリウム等のアジ化物、過硫酸アンモニウム等の過硫酸塩等を例示することができる。しかし、これら酸化剤のうち、反応によって塩類が副生しないという点で過酸化水素又はオゾンを使用することが最も望ましい。酸化剤の添加方法としては、共沈ゲル生成時、例えば水溶性セリウム塩と水溶性ジルコニウム塩の混合塩水溶液に添加しても良いし、生成した共沈ゲルに添加しても良く、また共沈ゲルに酸を添加した後に添加してもよい。 By the way, when the solid solution composition is cerium-rich, the gel is difficult to be peptized even under the above-described peptization conditions, and may require higher temperature or longer heating. In such a case, peptization can be easily performed by adding 0.2 mol or more of oxidizing agent to 1 mol of Ce contained in the gel. Examples of the oxidizing agent used in the present invention include hydrogen peroxide, ozone, azides such as sodium azide, persulfates such as ammonium persulfate, and the like. However, among these oxidizing agents, it is most desirable to use hydrogen peroxide or ozone in that no salts are by-produced by the reaction. The oxidizing agent may be added at the time of coprecipitation gel formation, for example, it may be added to a mixed salt aqueous solution of water-soluble cerium salt and water-soluble zirconium salt, or may be added to the generated coprecipitation gel. You may add after adding an acid to a precipitation gel.
このようにして得られた本発明のセリア−ジルコニア固溶体ゾルはその後、１５０℃以下で乾燥することでセリア−ジルコニア固溶体ゾル用粉体とすることができる。本発明においてセリア−ジルコニア固溶体ゾル用粉体とは、その粉体を水に再び懸濁させたときに本発明の５〜１００ｎｍの平均粒子径を有するゾルに戻ることを意味する。乾燥粉体は８０質量％以上のセリア−ジルコニア粒子を含むことになり、そのまま、あるいは少量の水に分散することによりさらに高濃度で使用することができる。 The ceria-zirconia solid solution sol of the present invention thus obtained can be dried at 150 ° C. or lower to obtain a powder for ceria-zirconia solid solution sol. In the present invention, the powder for ceria-zirconia solid solution sol means returning to the sol having an average particle diameter of 5 to 100 nm of the present invention when the powder is suspended again in water. The dry powder contains 80% by mass or more of ceria-zirconia particles, and can be used at a higher concentration as it is or when dispersed in a small amount of water.
乾燥方法としては噴霧乾燥、静置乾燥、気流乾燥など通常用いられる方法が採用できる。乾燥温度に関しては、ゾル粒子に吸着している塩酸や硝酸が遊離しない温度で乾燥することが重要である。よって、乾燥温度としては１５０℃以下が好ましい。 As a drying method, a commonly used method such as spray drying, stationary drying, or airflow drying can be employed. Regarding the drying temperature, it is important to dry at a temperature at which hydrochloric acid and nitric acid adsorbed on the sol particles are not liberated. Therefore, the drying temperature is preferably 150 ° C. or lower.
次にオキシカルボン酸で安定化されたゾルについて説明する。本発明によるオキシカルボン酸で安定化されたゾルは、硝酸や塩酸を用いることができない場合に有用であり、特にアルカリ性のゾルが得られることが特徴である。即ち、本発明は、塩酸又は硝酸で安定化されたセリア−ジルコニア固溶ゾルに、そのゾルに含まれるＣｅとＺｒのモル数の合計に対してモル比０.２〜２.０のオキシカルボン酸を添加した後、塩基でｐＨを７以上にすることを特徴とするオキシカルボン酸で安定化されたセリア−ジルコニア固溶体ゾルに関する。 Next, the sol stabilized with oxycarboxylic acid will be described. A sol stabilized with oxycarboxylic acid according to the present invention is useful when nitric acid or hydrochloric acid cannot be used, and is characterized in that an alkaline sol can be obtained. That is, the present invention provides a ceria-zirconia solid solution sol stabilized with hydrochloric acid or nitric acid in an oxycarboxylic acid having a molar ratio of 0.2 to 2.0 with respect to the total number of moles of Ce and Zr contained in the sol. The present invention relates to a ceria-zirconia solid solution sol stabilized with an oxycarboxylic acid, wherein the pH is set to 7 or more with a base after addition of an acid.
以下、オキシカルボン酸で安定化されたセリア−ジルコニア固溶体ゾルの製造方法に関して、硝酸で安定化されたセリア−ジルコニア固溶体ゾルを原料とした場合について詳述する。本発明の硝酸で安定化されたセリア−ジルコニア固溶体ゾルに対して所定量のオキシカルボン酸を添加した後、塩基を添加してｐＨを７以上にすることで、先ず硝酸とオキシカルボン酸で分散したアルカリ性のセリア−ジルコニア固溶体ゾルを得ることができる。本発明に用いるオキシカルボン酸の種類に関しては、乳酸、クエン酸、リンゴ酸、酒石酸等が例示でき、殊にクエン酸やリンゴ酸が好ましい。一方、本発明に用いる塩基としては、水酸化アルカリ、アンモニア、アミン類のいずれでもよいが、水酸化アルカリはナトリウム、カリウム又はリチウムがゾル中に残存することから、一般的にアンモニアが工業的に好ましく利用することができる。オキシカルボン酸の量に関しては、硝酸で安定化されたセリア−ジルコニア固溶体ゾルに含まれるＣｅとＺｒのモル数の合計に対してモル比０.２〜２．０の範囲で添加でき、アンモニアの添加量に関しては、ｐＨを７以上、好ましくは８〜１０になるように添加すればよい。 Hereinafter, the case where a ceria-zirconia solid solution sol stabilized with nitric acid is used as a raw material will be described in detail with respect to a method for producing a ceria-zirconia solid solution sol stabilized with oxycarboxylic acid. After adding a predetermined amount of oxycarboxylic acid to the ceria-zirconia solid solution sol stabilized with nitric acid according to the present invention, the base is added to make the pH 7 or higher, so that it is first dispersed with nitric acid and oxycarboxylic acid. An alkaline ceria-zirconia solid solution sol can be obtained. Examples of the oxycarboxylic acid used in the present invention include lactic acid, citric acid, malic acid, tartaric acid and the like, and citric acid and malic acid are particularly preferable. On the other hand, the base used in the present invention may be any of alkali hydroxide, ammonia, and amines. However, since alkali hydroxide has sodium, potassium or lithium remaining in the sol, ammonia is generally industrially used. It can be preferably used. Regarding the amount of oxycarboxylic acid, it can be added in a molar ratio of 0.2 to 2.0 with respect to the total number of moles of Ce and Zr contained in the ceria-zirconia solid solution sol stabilized with nitric acid. Regarding the addition amount, the pH may be added to 7 or more, preferably 8 to 10.
このようにして得られたゾルは硝酸とオキシカルボン酸を共に含んだ状態でも安定であるが、必要に応じて、更に限外ろ過等を用いて洗浄すれば硝酸が優先的に除去され、最終的にオキシカルボン酸のみで分散したゾルを得ることができる。上記方法で得られるゾルはアルカリ性で安定であり、用途、例えば他のアルカリ性原料と混合する場合、殊に有利に利用することができる。本発明のセリア−ジルコニア固溶体ゾルをアルカリ型に変性する際のゾルの濃度に関しては、特段限定されないが、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として通常１〜３０質量％の濃度で処理することができる。 The sol thus obtained is stable even in a state containing both nitric acid and oxycarboxylic acid. However, if necessary, nitric acid is preferentially removed by further washing using ultrafiltration or the like. Thus, a sol dispersed only with oxycarboxylic acid can be obtained. The sol obtained by the above method is alkaline and stable, and can be used particularly advantageously when used, for example, when mixed with other alkaline raw materials. The concentration of the sol when the ceria-zirconia solid solution sol of the present invention is modified to an alkali type is not particularly limited, but is usually 1 to 30% by mass as the total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ). Can be processed at different concentrations.
以上述べてきたように本発明のセリア−ジルコニア固溶体ゾルは、アルミナゾル等と混合してコージェライト製ハニカム等に含浸してセリア−ジルコニア固溶体を担持した触媒を作成することができる。このようにして得られた触媒は、本発明のセリア−ジルコニア固溶体粒子の良好な分散性の結果、高温で処理された後でも高い効果を示す。発明のセリア−ジルコニア固溶体ゾルの用途に関しては、自動車用触媒の他、工業用各種触媒や酸素センサー用材料等として使用することができる。 As described above, the ceria-zirconia solid solution sol of the present invention can be mixed with alumina sol or the like and impregnated in a cordierite honeycomb or the like to prepare a catalyst carrying the ceria-zirconia solid solution. The catalyst thus obtained shows a high effect even after being treated at high temperature as a result of the good dispersibility of the ceria-zirconia solid solution particles of the present invention. Regarding the use of the ceria-zirconia solid solution sol of the invention, it can be used as various industrial catalysts, oxygen sensor materials, etc. in addition to automobile catalysts.
以下に、本発明を実施例により具体的に説明するが、本発明はこれらに限定されるものではない。尚、実施例において％は、特に断らない限り全て質量％を示す。また、実施例中の限外濾過装置は、限外濾過膜として「ラボモジュール」型式ＳＬＰ−１０５３（旭化成(株)製）を用いた。 EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In Examples, “%” means “% by mass” unless otherwise specified. Moreover, the ultrafiltration apparatus in an Example used "lab module" model SLP-1053 (made by Asahi Kasei Co., Ltd.) as an ultrafiltration membrane.
本発明のセリア−ジルコニア固溶体ゾル、易分散性粉体及びそれらの焼成品の物性は、以下の方法で測定した。 The physical properties of the ceria-zirconia solid solution sol, the easily dispersible powder and the fired products of the present invention were measured by the following methods.
（１）平均粒子径の測定
平均粒子径は、動的光散乱色粒度分布測定装置LB-500（堀場製作所(株)製）を用いて測定した。
（２）ヘイズ率の測定
ヘイズ率は、色差計COH-300A（日本電色工業(株)製）を用いて測定した。測定条件としては、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として１．０％に調整した試料を光路長１ｃｍのガラスセルに入れて測定した。
（３）電気伝導度の測定
電気伝導度は、電気伝導度計CM-14P（TOA ELECTRON Ltd．製）を用いて測定した。
（４）X線回折の測定
X線回折は、Ｘ線回折装置 XRD-7000（島津製作所(株)製）を用いて測定した。
（５）保存安定性の試験
保存安定性の試験は、試料を５０ｃｃ容サンプル瓶に入れて封入し、５０℃の恒温槽で行なった。
(1) Measurement of average particle diameter The average particle diameter was measured using a dynamic light scattering color particle size distribution analyzer LB-500 (manufactured by Horiba, Ltd.).
(2) Measurement of haze ratio The haze ratio was measured using a color difference meter COH-300A (manufactured by Nippon Denshoku Industries Co., Ltd.). As a measurement condition, a sample adjusted to 1.0% as a total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) was put in a glass cell having an optical path length of 1 cm and measured.
(3) Measurement of electric conductivity The electric conductivity was measured using an electric conductivity meter CM-14P (manufactured by TOA ELECTRON Ltd.).
(4) X-ray diffraction measurement
X-ray diffraction was measured using an X-ray diffractometer XRD-7000 (manufactured by Shimadzu Corporation).
(5) Storage stability test The storage stability test was performed by placing the sample in a 50 cc sample bottle and enclosing it in a 50 ° C constant temperature bath.
[実施例１]
１．０％アンモニア水４３１２ｇにＣｅＯ２換算で１．０％の塩化セリウム溶液（太陽鉱工(株)製）５０００ｇ及びＺｒＯ２換算で１．０％のオキシ塩化ジルコニウム（第一稀元素化学工業(株)製：ジルコゾールZC−２０）３５８０ｇの混合塩溶液（Ce/Zr（モル比）＝５０/５０）を撹拌下で添加し、共沈ゲルを生成させた。次いで限外濾過装置により濾液の電気伝導度が５０ｍＳ/ｍ以下になるまでゲル中の塩化アンモニウムを除去し、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として２．０％のセリア−ジルコニア固溶体ゲル溶液を得た。次いで、ゲル中に含まれるＣｅとＺｒのモル数の合計に対してモル比で０．４の５．０％硝酸溶液を添加し、オートクレーブで１２０℃/３ｈの水熱処理を行ない、セリア−ジルコニア固溶体ゾルを得た。更に限外濾過装置により濾液の電気伝導度が５０ｍＳ/ｍ以下になるまで濾過及び濃縮を行い、１０．０％のセリア−ジルコニア固溶体ゾルを得た。
得られたゾルは、平均粒子径１６ｎｍ、電気伝導度０．５Ｓ／ｍ、ｐＨ２．３、ヘイズ率は１．０％であった。また１ヶ月間での保存安定性は増粘や沈殿物の発生もなく良好であった。
[Example 1]
1.0% aqueous ammonia 4312G 1.0% cerium chloride in terms of CeO 2 solution (manufactured by Taiyo ore Engineering (Co.)) 5000 g and in terms of ZrO 2 with 1.0% of zirconium oxychloride (Daiichi Kigenso Kagaku Kogyo Co., Ltd .: Zircosol ZC-20) 3580 g of a mixed salt solution (Ce / Zr (molar ratio) = 50/50) was added with stirring to produce a coprecipitated gel. Next, the ammonium chloride in the gel was removed with an ultrafiltration device until the electrical conductivity of the filtrate was 50 mS / m or less, and the total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) was 2.0%. A ceria-zirconia solid solution gel solution was obtained. Next, a 5.0% nitric acid solution having a molar ratio of 0.4 with respect to the total number of moles of Ce and Zr contained in the gel was added, and hydrothermal heat treatment at 120 ° C./3 h was performed in an autoclave, and ceria-zirconia. A solid solution sol was obtained. Further, filtration and concentration were carried out with an ultrafiltration device until the electric conductivity of the filtrate was 50 mS / m or less, thereby obtaining 10.0% ceria-zirconia solid solution sol.
The obtained sol had an average particle diameter of 16 nm, an electric conductivity of 0.5 S / m, a pH of 2.3, and a haze ratio of 1.0%. In addition, the storage stability for one month was good without thickening and generation of precipitates.
得られたゾルを１００℃で乾燥させてセリア−ジルコニア固溶体ゾル用粉体を得た。次いで、これを水中に再分散させることで再び元の１０．０％のゾルを得ることができた。再分散によって得られたゾルの平均粒子径は１７nmであった。尚、セリア−ジルコニア固溶体ゾル用粉体のＸ線回折パターンを図１に示す。図１から明らかなように本発明のゾルの１００℃乾燥品は、弱いピークではあるがセリア−ジルコニア固溶体の回折パターンを示している。また、参考のため５００℃及び１０００℃での１時間熱処理後のＸ線回折は、図１に示すようにＡＳＴＭカードＮｏ．３８−１４３６で示される明確なセリア−ジルコニア固溶体を示す回折パターンを示している。 The obtained sol was dried at 100 ° C. to obtain a powder for ceria-zirconia solid solution sol. This was then re-dispersed in water, and the original 10.0% sol could be obtained again. The average particle size of the sol obtained by redispersion was 17 nm. An X-ray diffraction pattern of the powder for ceria-zirconia solid solution sol is shown in FIG. As is clear from FIG. 1, the 100 ° C. dried product of the sol of the present invention shows a diffraction pattern of a ceria-zirconia solid solution although it has a weak peak. For reference, X-ray diffraction after heat treatment at 500 ° C. and 1000 ° C. for 1 hour is shown in FIG. The diffraction pattern showing a clear ceria-zirconia solid solution shown at 38-1436 is shown.
[実施例２]
２．０％アンモニア水溶液３７４２ｇにＣｅＯ２換算で２．０％の塩化セリウム溶液（太陽鉱工(株)製）２５００ｇ及びＺｒＯ２換算で２．０％のオキシ塩化ジルコニウム（第一稀元素化学工業(株)製：ジルコゾールZC−２０）４１７６ｇの混合塩溶液（Ce/Zr（モル比）＝３０/７０）を撹拌下で添加し、共沈ゲルを生成させた。次いで限外濾過装置により濾液の電気伝導度が５０ｍＳ/ｍ以下になるまでゲル中の塩化アンモニウムを除去し、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として２．０％のセリア−ジルコニア固溶体ゲル溶液を得た。次いで、ゲル中に含まれるＣｅとＺｒのモル数の合計に対してモル比で０．５６の５．０％塩酸溶液を添加し、オートクレーブで１００℃/５ｈの水熱処理を行ない、セリア−ジルコニア固溶体ゾルを得た。更に限外濾過装置により濾液の電気伝導度が５０ｍＳ/ｍ以下になるまで濾過及び濃縮を行い、１０．０％のセリア−ジルコニア固溶体ゾルを得た。
[Example 2]
2.0% aqueous ammonia solution 3742g in terms of CeO 2 2.0% cerium chloride solution (manufactured by Taiyo ore Engineering (Co.)) 2500 g and in terms of ZrO 2 with 2.0% zirconium oxychloride (Daiichi Kigenso Kagaku Kogyo Co., Ltd .: Zircozole ZC-20) 4176 g of a mixed salt solution (Ce / Zr (molar ratio) = 30/70) was added with stirring to produce a coprecipitated gel. Next, the ammonium chloride in the gel was removed with an ultrafiltration device until the electrical conductivity of the filtrate was 50 mS / m or less, and the total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) was 2.0%. A ceria-zirconia solid solution gel solution was obtained. Next, a 5.0% hydrochloric acid solution having a molar ratio of 0.56 with respect to the total number of moles of Ce and Zr contained in the gel was added, and hydrothermal heat treatment at 100 ° C./5 h was performed in an autoclave, and ceria-zirconia. A solid solution sol was obtained. Further, filtration and concentration were carried out with an ultrafiltration device until the electric conductivity of the filtrate was 50 mS / m or less, thereby obtaining 10.0% ceria-zirconia solid solution sol.
得られたゾルは、平均粒子径１３ｎｍ、電気伝導度０．４Ｓ／ｍ、ｐＨ２．４、ヘイズ率は０．９％であった。また１ヶ月間での保存安定性は増粘や沈殿物の発生もなく良好であった。このゾルを１００℃で恒量になるまで乾燥した後、これを５００℃で１時間熱処理した後のＸ線回折では、図２に示すようにＡＳＴＭカードＮｏ．３８−１４３７とＡＳＴＭカードＮｏ．３８−１４３６に近似した明確なセリア−ジルコニア固溶体を示す回折パターンを示している。 The obtained sol had an average particle diameter of 13 nm, an electric conductivity of 0.4 S / m, a pH of 2.4, and a haze ratio of 0.9%. In addition, the storage stability for one month was good without thickening and generation of precipitates. The sol was dried to a constant weight at 100 ° C., and then heat-treated at 500 ° C. for 1 hour. In the X-ray diffraction, as shown in FIG. 38-1437 and ASTM card no. The diffraction pattern showing a clear ceria-zirconia solid solution approximated to 38-1436 is shown.
[実施例３]
１．０％アンモニア水２９５２ｇにＣｅＯ２換算で１．０％の塩化セリウム溶液（太陽鉱工(株)製）５０００ｇ及びＺｒＯ２換算で１．０％のオキシ塩化ジルコニウム（第一稀元素化学工業(株)製：ジルコゾールZC−２０）１５３４ｇの混合塩溶液（Ce/Zr（モル比）＝７０/３０）を撹拌下で添加し、共沈ゲルを生成させた。次いで限外濾過装置により濾液の電気伝導度が５０ｍＳ/ｍ以下になるまでゲル中の塩化アンモニウムを除去し、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として２．０％のセリア−ジルコニア固溶体ゲル溶液を得た。次いで、ゲル中に含まれるＣｅ１モルに対して１．０モルの３５．０％過酸化水素を添加した。さらにＣｅとＺｒのモル数の合計に対してモル比で０．２４の５．０％塩酸溶液を添加し、オートクレーブで１００℃/５ｈの水熱処理を行ない、セリア−ジルコニア固溶体ゾルを得た。
次にこのゾルに、ゾル中に含まれるＣｅとＺｒのモル数の合計に対してモル比で０．３の１０．０％クエン酸溶液を添加し、更に３．０％アンモニア水を用いてゾルｐH９．５にした後、限外濾過装置により濾液の電気伝導度が５０ｍＳ/ｍ以下になるまで濾過及び濃縮を行い、１０．０％のセリア−ジルコニア固溶体ゾルを得た。
[Example 3]
1.0% aqueous ammonia 2952G 1.0% cerium chloride in terms of CeO 2 solution (manufactured by Taiyo ore Engineering (Co.)) 5000 g and in terms of ZrO 2 with 1.0% of zirconium oxychloride (Daiichi Kigenso Kagaku Kogyo Co., Ltd .: Zircozole ZC-20 (1534 g) mixed salt solution (Ce / Zr (molar ratio) = 70/30) was added under stirring to produce a coprecipitated gel. Next, the ammonium chloride in the gel was removed with an ultrafiltration device until the electrical conductivity of the filtrate was 50 mS / m or less, and the total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) was 2.0%. A ceria-zirconia solid solution gel solution was obtained. Next, 1.0 mol of 35.0% hydrogen peroxide was added to 1 mol of Ce contained in the gel. Furthermore, a 5.0% hydrochloric acid solution having a molar ratio of 0.24 with respect to the total number of moles of Ce and Zr was added, and hydrothermal treatment was performed at 100 ° C./5 h in an autoclave to obtain a ceria-zirconia solid solution sol.
Next, to this sol, a 10.0% citric acid solution having a molar ratio of 0.3 with respect to the total number of moles of Ce and Zr contained in the sol was added, and further using 3.0% aqueous ammonia. After making the sol pH 9.5, the filtrate was filtered and concentrated with an ultrafiltration device until the electric conductivity of the filtrate was 50 mS / m or less to obtain 10.0% ceria-zirconia solid solution sol.
得られたゾルは、平均粒子径１３ｎｍ、電気伝導度０．５Ｓ／ｍ、ｐＨ８．２、ヘイズ率は０．２％であった。また１ヶ月間での保存安定性は増粘や沈殿物の発生もなく良好であった。このゾルを１００℃で恒量になるまで乾燥した後、これを５００℃で１時間熱処理した後のＸ線回折では、図２に示すようにＡＳＴＭカードＮｏ．２８−２７１に近似した明確なセリア−ジルコニア固溶体を示す回折パターンを示している。 The obtained sol had an average particle diameter of 13 nm, an electric conductivity of 0.5 S / m, a pH of 8.2, and a haze ratio of 0.2%. In addition, the storage stability for one month was good without thickening and generation of precipitates. The sol was dried to a constant weight at 100 ° C. and then heat-treated at 500 ° C. for 1 hour. In the X-ray diffraction, as shown in FIG. A diffraction pattern showing a clear ceria-zirconia solid solution approximating 28-271 is shown.
[比較例１]
１．０％アンモニア水４３１２ｇにＣｅＯ２換算で１．０％の塩化セリウム溶液（太陽鉱工(株)製）５０００ｇ及びＺｒＯ２換算で１．０％のオキシ塩化ジルコニウム（第一稀元素化学工業(株)製：ジルコゾールZC−２０）３５８０ｇの混合塩溶液（Ce/Zr（モル比）＝５０/５０）を撹拌下で添加し、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として０．７％の共沈ゲルを生成させた。このゲルを洗浄することなく、このゲル中に含まれるＣｅとＺｒのモル数の合計に対してモル比で０．４の５．０％硝酸溶液を添加し、オートクレーブで１２０℃/３ｈの水熱処理を行なった。水熱処理をおこなったゲルの平均粒子径は２．２μｍ、ヘイズ率は、８９．７％であり、解膠は認められなかった。
[Comparative Example 1]
1.0% aqueous ammonia 4312G 1.0% cerium chloride in terms of CeO 2 solution (manufactured by Taiyo ore Engineering (Co.)) 5000 g and in terms of ZrO 2 with 1.0% of zirconium oxychloride (Daiichi Kigenso Kagaku Kogyo Co., Ltd .: Zircozole ZC-20) 3580 g of mixed salt solution (Ce / Zr (molar ratio) = 50/50) was added with stirring, and cerium (as CeO 2 ) and zirconium (as ZrO 2 ) were combined. An amount of 0.7% coprecipitated gel was produced. Without washing the gel, a 5.0% nitric acid solution having a molar ratio of 0.4 to the total number of moles of Ce and Zr contained in the gel was added, and water was added at 120 ° C./3 h with an autoclave. Heat treatment was performed. The average particle size of the gel subjected to hydrothermal treatment was 2.2 μm, the haze ratio was 89.7%, and no peptization was observed.
［比較例２］
１．０％アンモニア水４３１２ｇにＣｅＯ２換算で１．０％の塩化セリウム溶液（太陽鉱工(株)製）５０００ｇ及びＺｒＯ２換算で１．０％のオキシ塩化ジルコニウム（第一稀元素化学工業(株)製：ジルコゾールZC−２０）３５８０ｇの混合塩溶液（Ce/Zr（モル比）＝５０/５０）を撹拌下で添加し、共沈ゲルを生成させた。次いで限外濾過装置により濾液の電気伝導度が５０ｍＳ/ｍ以下になるまでゲル中の塩化アンモニウムを除去し、セリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として２．０％のセリア−ジルコニア固溶体ゲルを得た。
次いで、ゲル中に含まれるＣｅとＺｒの合計モル数に対してモル比で０．４の５．０％シュウ酸溶液を添加し、オートクレーブで１００℃/５ｈの水熱処理を行なった。水熱処理をおこなったゲルの平均粒子径は２．５μｍ、ヘイズ率は、９０．３％であり、解膠は認められなかった。
[Comparative Example 2]
1.0% aqueous ammonia 4312G 1.0% cerium chloride in terms of CeO 2 solution (manufactured by Taiyo ore Engineering (Co.)) 5000 g and in terms of ZrO 2 with 1.0% of zirconium oxychloride (Daiichi Kigenso Kagaku Kogyo Co., Ltd .: Zircosol ZC-20) 3580 g of a mixed salt solution (Ce / Zr (molar ratio) = 50/50) was added with stirring to produce a coprecipitated gel. Next, the ammonium chloride in the gel was removed with an ultrafiltration device until the electrical conductivity of the filtrate was 50 mS / m or less, and the total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) was 2.0%. A ceria-zirconia solid solution gel was obtained.
Subsequently, a 5.0% oxalic acid solution having a molar ratio of 0.4 with respect to the total number of moles of Ce and Zr contained in the gel was added, and hydrothermal treatment was performed at 100 ° C./5 h in an autoclave. The average particle size of the gel subjected to hydrothermal treatment was 2.5 μm, the haze ratio was 90.3%, and no peptization was observed.
［比較例３］
ＣｅＯ２換算で２．０％の塩化セリウム溶液（太陽鉱工(株)製）２５００ｇ及びＺｒＯ２換算で２．０％のオキシ塩化ジルコニウム（第一稀元素化学工業(株)製：ジルコゾールZC−２０）１１９３ｇの混合塩溶液（Ce/Zr（モル比）＝６０/４０）をセリウム（ＣｅＯ２として）とジルコニウム（ＺｒＯ２として）の合量として１．５％溶液に希釈した後、Ｃｅに対して等モルの１０．０％ペルオクソ二硫酸アンモニウム溶液を添加して混合した。次いで、これをステンレス製の容器に収容し、内容物を撹拌しながら１００℃/１６８ｈの加水分解を行った。得られた生成物の平均粒子径は１．５μｍであり、沈降性を有する粗大粒子であり、分散性に優れた微粒子を得ることはできなかった。
[Comparative Example 3]
2500 g of a cerium chloride solution of 2.0% in terms of CeO 2 (manufactured by Taiyo Mining Co., Ltd.) and 2.0% of zirconium oxychloride in terms of ZrO 2 (manufactured by Daiichi Rare Element Chemical Industries, Ltd .: Zircosol ZC- 20) After diluting 1193 g of the mixed salt solution (Ce / Zr (molar ratio) = 60/40) as a total amount of cerium (as CeO 2 ) and zirconium (as ZrO 2 ) to a 1.5% solution, On the other hand, equimolar 10.0% ammonium peroxodisulfate solution was added and mixed. Subsequently, this was accommodated in a stainless steel container and subjected to hydrolysis at 100 ° C./168 h while stirring the contents. The resulting product had an average particle size of 1.5 μm, coarse particles having sedimentation properties, and fine particles having excellent dispersibility could not be obtained.
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| JP4918880B2 (en) * | 2007-05-23 | 2012-04-18 | 日産化学工業株式会社 | Method for producing zirconia sol |
| JP2009067666A (en) * | 2007-09-14 | 2009-04-02 | Daiichi Kigensokagaku Kogyo Co Ltd | Ceria-zirconia solid solution sol and its production method |
| JP5253095B2 (en) * | 2007-12-20 | 2013-07-31 | 日揮触媒化成株式会社 | Method for producing zirconia sol |
| JP5400431B2 (en) * | 2009-03-05 | 2014-01-29 | トヨタ自動車株式会社 | Exhaust gas purification catalyst and method for producing the same |
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| JP7405078B2 (en) | 2018-06-29 | 2023-12-26 | 堺化学工業株式会社 | Method for producing ceria-zirconia complex oxide dispersion |
| CN113149071B (en) * | 2021-04-19 | 2022-11-25 | 中民驰远实业有限公司 | Synthetic nano ZrO 2 Method for preparing powder |
| CN114957192B (en) * | 2022-06-06 | 2023-10-10 | 天津大学 | Method for preparing cyclic carbonate by catalyzing carbon dioxide with cerium-based catalyst |
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