JP5116276B2 - Powder comprising oxide microcrystal particles, catalyst using the same, and method for producing the same - Google Patents
Powder comprising oxide microcrystal particles, catalyst using the same, and method for producing the same Download PDFInfo
- Publication number
- JP5116276B2 JP5116276B2 JP2006268317A JP2006268317A JP5116276B2 JP 5116276 B2 JP5116276 B2 JP 5116276B2 JP 2006268317 A JP2006268317 A JP 2006268317A JP 2006268317 A JP2006268317 A JP 2006268317A JP 5116276 B2 JP5116276 B2 JP 5116276B2
- Authority
- JP
- Japan
- Prior art keywords
- particles
- oxide
- powder
- crystal
- plane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000002245 particle Substances 0.000 title claims description 251
- 239000000843 powder Substances 0.000 title claims description 106
- 239000013081 microcrystal Substances 0.000 title claims description 84
- 239000003054 catalyst Substances 0.000 title claims description 32
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 239000013078 crystal Substances 0.000 claims description 158
- 229910052760 oxygen Inorganic materials 0.000 claims description 53
- 239000001301 oxygen Substances 0.000 claims description 53
- -1 oxygen ion Chemical class 0.000 claims description 45
- 150000001768 cations Chemical class 0.000 claims description 26
- 238000006243 chemical reaction Methods 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 26
- 229910052684 Cerium Inorganic materials 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 12
- 229910052746 lanthanum Inorganic materials 0.000 claims description 12
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 9
- 125000004432 carbon atom Chemical group C* 0.000 claims description 7
- 239000002105 nanoparticle Substances 0.000 claims description 7
- 230000007704 transition Effects 0.000 claims description 7
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical group [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 6
- 229910000510 noble metal Inorganic materials 0.000 claims description 6
- 230000002194 synthesizing effect Effects 0.000 claims description 3
- 150000001732 carboxylic acid derivatives Chemical class 0.000 claims 3
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 51
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 51
- 239000010419 fine particle Substances 0.000 description 37
- 230000000052 comparative effect Effects 0.000 description 26
- 238000000635 electron micrograph Methods 0.000 description 26
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 21
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 15
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 14
- 230000003197 catalytic effect Effects 0.000 description 14
- 239000002159 nanocrystal Substances 0.000 description 14
- 239000000126 substance Substances 0.000 description 14
- 239000000463 material Substances 0.000 description 13
- 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 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- WWZKQHOCKIZLMA-UHFFFAOYSA-N Caprylic acid Natural products CCCCCCCC(O)=O WWZKQHOCKIZLMA-UHFFFAOYSA-N 0.000 description 11
- GONOPSZTUGRENK-UHFFFAOYSA-N benzyl(trichloro)silane Chemical compound Cl[Si](Cl)(Cl)CC1=CC=CC=C1 GONOPSZTUGRENK-UHFFFAOYSA-N 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- FUZZWVXGSFPDMH-UHFFFAOYSA-N n-hexanoic acid Natural products CCCCCC(O)=O FUZZWVXGSFPDMH-UHFFFAOYSA-N 0.000 description 11
- 238000012360 testing method Methods 0.000 description 11
- 239000000203 mixture Substances 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 9
- 229910044991 metal oxide Inorganic materials 0.000 description 9
- 150000004706 metal oxides Chemical class 0.000 description 9
- 238000004458 analytical method Methods 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 8
- 239000003607 modifier Substances 0.000 description 7
- 238000000746 purification Methods 0.000 description 7
- 239000000758 substrate Substances 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 239000012528 membrane Substances 0.000 description 6
- UNJPQTDTZAKTFK-UHFFFAOYSA-K cerium(iii) hydroxide Chemical compound [OH-].[OH-].[OH-].[Ce+3] UNJPQTDTZAKTFK-UHFFFAOYSA-K 0.000 description 5
- 238000002524 electron diffraction data Methods 0.000 description 5
- 229930195733 hydrocarbon Natural products 0.000 description 5
- 150000002430 hydrocarbons Chemical class 0.000 description 5
- 238000006722 reduction reaction Methods 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 239000000725 suspension Substances 0.000 description 5
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 239000002585 base Substances 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 229910002651 NO3 Inorganic materials 0.000 description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 150000001735 carboxylic acids Chemical class 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 229910052878 cordierite Inorganic materials 0.000 description 3
- 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 3
- 230000000694 effects Effects 0.000 description 3
- 238000002003 electron diffraction Methods 0.000 description 3
- 229910052741 iridium Inorganic materials 0.000 description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 229910052703 rhodium Inorganic materials 0.000 description 3
- 229910052707 ruthenium Inorganic materials 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 229910052718 tin Inorganic materials 0.000 description 3
- 229910052725 zinc Inorganic materials 0.000 description 3
- GYSCBCSGKXNZRH-UHFFFAOYSA-N 1-benzothiophene-2-carboxamide Chemical compound C1=CC=C2SC(C(=O)N)=CC2=C1 GYSCBCSGKXNZRH-UHFFFAOYSA-N 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- GHVNFZFCNZKVNT-UHFFFAOYSA-N Decanoic acid Natural products CCCCCCCCCC(O)=O GHVNFZFCNZKVNT-UHFFFAOYSA-N 0.000 description 2
- 229910052693 Europium Inorganic materials 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 230000010718 Oxidation Activity Effects 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 229910052785 arsenic Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 229910052793 cadmium Inorganic materials 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 239000010436 fluorite Substances 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 229910052733 gallium Inorganic materials 0.000 description 2
- 229910052732 germanium Inorganic materials 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 150000004679 hydroxides Chemical class 0.000 description 2
- 229910052738 indium Inorganic materials 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052745 lead Inorganic materials 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 229910052762 osmium Inorganic materials 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 229910052716 thallium Inorganic materials 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910020599 Co 3 O 4 Inorganic materials 0.000 description 1
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 1
- 239000005751 Copper oxide Substances 0.000 description 1
- MHZGKXUYDGKKIU-UHFFFAOYSA-N Decylamine Chemical compound CCCCCCCCCCN MHZGKXUYDGKKIU-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910006404 SnO 2 Inorganic materials 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 229910052769 Ytterbium Inorganic materials 0.000 description 1
- 239000003082 abrasive agent Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 238000000149 argon plasma sintering Methods 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229910000431 copper oxide Inorganic materials 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 125000000753 cycloalkyl group Chemical group 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 229910001849 group 12 element Inorganic materials 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012770 industrial material Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- VASIZKWUTCETSD-UHFFFAOYSA-N manganese(II) oxide Inorganic materials [Mn]=O VASIZKWUTCETSD-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000010534 mechanism of action Effects 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000000235 small-angle X-ray scattering Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000002336 sorption--desorption measurement Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 125000004434 sulfur atom Chemical group 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- XLOMVQKBTHCTTD-UHFFFAOYSA-N zinc oxide Inorganic materials [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 1
Description
本発明は、酸化物微結晶粒子からなる粉体、それを用いた触媒、並びにその製造方法に関する。 The present invention relates to a powder comprising fine oxide crystal particles, a catalyst using the same, and a method for producing the same.
微粒子、特にはナノメーターサイズの粒子（ナノ粒子）は、様々な特有の優れた性状・特性・機能を示すことから、材料・製品のすべてに対して、現状よりも高精度で、より小型化、より軽量化の要求を満たしている技術を実現するものとして期待されている。このようにナノ粒子は、セラミックスのナノ構造改質材、光機能コーティング材、電磁波遮蔽材料、二次電池用材料、蛍光材料、電子部品材料、磁気記録材料、研摩材料等の産業・工業材料、医薬品・化粧品材料等の高機能・高性能・高密度・高度精密化を可能にする材料として注目されている。 Fine particles, especially nanometer-sized particles (nanoparticles) exhibit various unique and excellent properties, characteristics, and functions, so they are more accurate and more compact than all current materials and products. It is expected to realize a technology that satisfies the demand for lighter weight. In this way, the nanoparticle is a ceramic nanostructure modifier, an optical functional coating material, an electromagnetic shielding material, a secondary battery material, a fluorescent material, an electronic component material, a magnetic recording material, an industrial material such as an abrasive material, It is attracting attention as a material that enables high functionality, high performance, high density, and high precision for pharmaceuticals and cosmetics.
このような状況の下、例えば特開２００３−４７８４９号公報（特許文献１）においては、アルミナにセリアを高分散させた担持基材に触媒金属元素を担持させてなる排ガス浄化用触媒であって、Ｘ線回折による（１１１）面の回折ピークの積分強度Ｉ１１１に対する（２００）面の回折ピークの積分強度Ｉ２００の比Ｉ２００／Ｉ１１１が０．４を超えるセリアを含んでいることを特徴とする排ガス浄化用触媒が開示されている。 Under such circumstances, for example, Japanese Patent Application Laid-Open No. 2003-47849 (Patent Document 1) is an exhaust gas purification catalyst in which a catalytic metal element is supported on a supporting base material in which ceria is highly dispersed in alumina. The ratio I 200 / I 111 of the integrated intensity I 200 of the (200) plane diffraction peak to the integrated intensity I 111 of the (111) plane diffraction peak by X-ray diffraction contains ceria that exceeds 0.4. A featured exhaust gas purification catalyst is disclosed.
しかしながら、特許文献１に記載の排ガス浄化用触媒においては、セリアをアルミナ担体に高分散状態で担持することでしか結晶面の制御を行うことができないため、結晶面の制御を行ったセリア単独の粒子を得ることができず、組成に大きな制約があるため、セリアに任意の成分を担持した組成物を得ることができないという問題があった。 However, in the exhaust gas purifying catalyst described in Patent Document 1, since the crystal plane can be controlled only by supporting ceria in a highly dispersed state on the alumina carrier, the ceria alone that has controlled the crystal plane is used. Since particles cannot be obtained and there is a great restriction on the composition, there is a problem that a composition in which an arbitrary component is supported on ceria cannot be obtained.
なお、特許文献１においては、前記の比Ｉ２００／Ｉ１１１が０．４を超えるという現象から（２００）面方向に成長したセリアの割合が多くなっているという結論が導かれているが、以下の理由によりその結論は不正確であると本発明者らは確信している。すなわち、同文献に記載のセリア粒子はアルミナ担体の間隙で任意の結晶方位で成長しているはずであり、Ｘ線回折の測定をする場合にもアルミナと分離するのは不可能であることから、任意の結晶方位を向いたままのはずである。そして、セリアを高分散状態にするということは、結晶子径が小さくなる傾向にあることから、前記の比Ｉ２００／Ｉ１１１が大きくなる現象は結晶子径の変化と関連した形で理解されるべきであり、（２００）面方向に成長したセリアの割合が多くなっているとは言えない。 In Patent Document 1, a conclusion that the ratio of ceria grown in the (200) plane direction is increased from the phenomenon that the ratio I 200 / I 111 exceeds 0.4 is derived. The inventors believe that the conclusion is inaccurate for the following reasons. That is, the ceria particles described in the same document should have grown in an arbitrary crystal orientation in the gap of the alumina carrier, and it is impossible to separate from alumina even when measuring X-ray diffraction. , It should remain in any crystal orientation. The fact that the ceria is in a highly dispersed state tends to decrease the crystallite diameter, and thus the phenomenon that the ratio I 200 / I 111 increases is understood in a form associated with the change in the crystallite diameter. It should not be said that the proportion of ceria grown in the (200) plane direction is increasing.
また、Ｋ．Ｚｈｏｕ ｅｔ ａｌ．，Ｊ．Ｃａｔａｌｙｓｉｓ ２２９（２００５）ｐ．２０６〜２１２（非特許文献１）においては、硝酸セリウムを水酸化ナトリウムで中和し、１００℃の水熱条件で１０時間処理し、洗浄しろ過した後に６０℃で乾燥し、さらに３５０℃で４時間焼成することで、太さが約２０ｎｍで長さが約２００ｎｍの棒状セリア単結晶が得られることが開示されている。そして、かかる棒状セリア単結晶は端面が（１１０）面からなり、側面が（１１０）面と（００１）面とからなる直方体であることが記載されており、さらに従来のセリアナノ粒子の主たる表面を構成する（１１１）面は非常に安定であるのに対して、（１１０）面は安定性がやや低く、（００１）面は表面エネルギーがより高く活性であることが記載されている。 K.K. Zhou et al. , J .; Catalysis 229 (2005) p. In 206-212 (Non-patent Document 1), cerium nitrate is neutralized with sodium hydroxide, treated under hydrothermal conditions of 100 ° C. for 10 hours, washed, filtered, dried at 60 ° C., and further at 350 ° C. It is disclosed that a rod-shaped ceria single crystal having a thickness of about 20 nm and a length of about 200 nm can be obtained by firing for 4 hours. It is described that the rod-like ceria single crystal is a rectangular parallelepiped having an end face made of (110) face and side faces made of (110) face and (001) face, and further the main surface of the conventional ceria nanoparticles. It is described that the (111) plane is very stable, whereas the (110) plane is slightly less stable and the (001) plane has a higher surface energy and is active.
しかしながら、非特許文献１に記載の棒状セリア単結晶においては、（００１）面が５０％以下であり、活性な（００１）面の比率をそれ以上に高めることはできないという問題があった。また、棒状セリア単結晶は、触媒スラリーを調製する際に少量の添加で高粘度化し易く、さらに混合過程で棒状結晶が破壊されて活性な（００１）面の比率が減少してしまうという問題もあった。 However, the rod-shaped ceria single crystal described in Non-Patent Document 1 has a problem that the (001) plane is 50% or less and the ratio of the active (001) plane cannot be increased further. In addition, the rod-shaped ceria single crystal is easily increased in viscosity by adding a small amount when preparing a catalyst slurry, and further, the rod-shaped crystal is broken during the mixing process and the ratio of the active (001) plane is reduced. there were.
さらに、特開２００５−１９３２３７号公報（特許文献２）においては、超臨界水熱合成法における反応場で、有機修飾剤を共存させて有機修飾金属酸化物微粒子を製造する方法が開示されており、実施例において硝酸セリウム水溶液に過酸化水素を加え、ヘキサン酸の共存下で高温高圧水熱合成によって有機修飾金属酸化物微粒子を製造する方法が記載されている。 Furthermore, Japanese Patent Application Laid-Open No. 2005-193237 (Patent Document 2) discloses a method for producing organic modified metal oxide fine particles in the presence of an organic modifier in a reaction field in a supercritical hydrothermal synthesis method. In the Examples, a method is described in which hydrogen peroxide is added to an aqueous cerium nitrate solution and organically modified metal oxide fine particles are produced by high-temperature, high-pressure hydrothermal synthesis in the presence of hexanoic acid.
しかしながら、特許文献２に記載の金属酸化物微粒子の製造方法においては、有機修飾により結晶成長が抑制されて結晶性の高いナノ粒子が得られるものの、同文献では得られた金属酸化物微粒子の結晶面については検討されておらず、実際に同文献に記載の方法は活性な結晶面からなる金属酸化物微粒子の比率の向上に限界があるという点で必ずしも十分なものではないということを本発明者らが見出した。
本発明は、上記従来技術の有する課題に鑑みてなされたものであり、活性な結晶面からなる酸化物微結晶粒子の比率を従来より大幅に向上させることが可能な酸化物微結晶粒子の製造方法を提供し、それによって従来は得ることができなかった活性な結晶面からなる酸化物微結晶粒子が５０質量％以上を占める粉体を提供し、さらにそれを用いて低温及び高温触媒活性に優れた触媒を提供することを目的とする。 The present invention has been made in view of the above-described problems of the prior art, and is capable of producing oxide microcrystal particles capable of significantly improving the ratio of oxide crystallite particles having an active crystal plane as compared with the prior art. The present invention provides a powder in which fine oxide crystal particles composed of active crystal planes, which could not be obtained in the past, account for 50% by mass or more, and further used for low temperature and high temperature catalytic activity. The object is to provide an excellent catalyst.
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、高温高圧の水熱合成法における反応場において特定の有機物質の共存下で酸化物微結晶粒子を合成する方法において、酸化物微結晶粒子を構成すべき特定の陽イオンの水酸化物を原料として用いることによって活性な結晶面からなる酸化物微結晶粒子の比率が大幅に向上することを見出し、本発明を完成するに至った。 As a result of intensive research aimed at achieving the above object, the present inventors have conducted oxidation in a method for synthesizing microcrystalline oxide particles in the presence of a specific organic substance in a reaction field in a high-temperature and high-pressure hydrothermal synthesis method. In order to complete the present invention, it has been found that the ratio of oxide microcrystal particles comprising active crystal planes is greatly improved by using as a raw material a hydroxide of a specific cation that should constitute the product microcrystal particles. It came.
すなわち、本発明の酸化物微結晶粒子からなる粉体の製造方法は、高温高圧の水熱合成法における反応場において、酸化物微結晶粒子を構成すべき陽イオンであるＣｅの水酸化物或いはＣｅ及びＬａの水酸化物から炭素数６〜１０のカルボン酸の共存下で酸化物微結晶粒子を合成することにより、最表面が酸素イオン層により構成された結晶面からなる酸化物微結晶粒子が５０質量％以上を占めている酸化物微結晶粒子からなる粉体を得ることを特徴とする方法である。本発明において、前記陽イオンの水酸化物と前記カルボン酸との比（モル比）は５：１〜１：１０であることが好ましい。 That is, the method for producing a powder composed of oxide fine crystal particles according to the present invention includes a hydroxide of Ce, which is a cation that should form oxide fine crystal particles, in a reaction field in a high-temperature and high-pressure hydrothermal synthesis method. Oxide microcrystal particles having an outermost surface composed of an oxygen ion layer by synthesizing oxide microcrystal particles in the presence of a carboxylic acid having 6 to 10 carbon atoms from a hydroxide of Ce and La Is a method characterized by obtaining a powder composed of oxide crystallite particles comprising 50% by mass or more . In the present invention, the ratio (molar ratio) between the cation hydroxide and the carboxylic acid is preferably 5: 1 to 1:10.
そして、このような本発明にかかる前記陽イオンの水酸化物としては、Ｃｅの水酸化物、或いはＣｅの水酸化物とＬａの水酸化物とを含有するものである。このようなＬａを含有する場合、その含有率は、ＣｅとＬａとの合計量を基準として３〜２０モル％であることが好ましい。また、本発明の酸化物微結晶粒子からなる粉体は、最表面が酸素イオン層により構成された結晶面（活性な結晶面）からなる酸化物微結晶粒子が５０質量％以上を占めていることを特徴とするものである。 Then, as the hydroxides of the cations according to the present invention, hydroxides of Ce, or Ru der those containing a hydroxide of Ce hydroxide and La. When such La is contained, the content is preferably 3 to 20 mol% based on the total amount of Ce and La . Also, the powder made of oxide fine crystal particles of the present invention, oxide fine crystal grains consisting of sintered outermost surface made by oxygen ion layer planes (active crystal surface) accounts for more than 50 wt% It is characterized by being.
本発明において、前記活性な結晶面が以下の（i）〜（iii）のうちの少なくとも一つの条件を満たしていることが好ましい。
（i）前記活性な結晶面を構成する最表面の酸素イオンに対する陽イオンの配位数が２以下であること。
（ii）前記活性な結晶面が、表面エネルギーが高く不安定な結晶面であること。
（iii）前記活性な結晶面からなる酸化物微結晶粒子がホタル石構造を有しており、前記活性な結晶面が（００１）面及び該（００１）面と結晶学的に等価な結晶面であること。
In the present invention, the active crystal plane preferably satisfies at least one of the following conditions (i) to (iii).
(I) The coordination number of cations with respect to oxygen ions on the outermost surface constituting the active crystal plane is 2 or less.
(Ii) The active crystal plane is an unstable crystal plane with high surface energy.
(Iii) The oxide microcrystalline particles comprising the active crystal plane have a fluorite structure, and the active crystal plane is a crystal plane that is crystallographically equivalent to the (001) plane and the (001) plane. Be.
また、本発明にかかる前記酸化物微結晶粒子を構成する陽イオンが、Ｃｅ、或いはＣｅとＬａとを含有するものである。このようなＬａを含有する場合、その含有率は、ＣｅとＬａとの合計量を基準として３〜２０モル％であることが好ましい。 Further, cations constituting the oxide fine crystal particles according to the present invention, Ce, or Ru der those containing Ce and La. When such La is contained, the content is preferably 3 to 20 mol% based on the total amount of Ce and La .
さらに、前記活性な結晶面からなる酸化物微結晶粒子としては、２ｎｍ〜３０ｎｍの範囲内の平均粒径を有するものであることが好ましく、単分散ナノ結晶粒子であることがより好ましい。 Furthermore, the oxide microcrystal particles comprising the active crystal plane preferably have an average particle size in the range of 2 nm to 30 nm, and more preferably monodisperse nanocrystal particles.
また、本発明の触媒は、前記本発明の酸化物微結晶粒子からなる粉体と、前記粉体の表面に担持された触媒活性種とを備えることを特徴とするものである。そして、このような触媒活性種としては、遷移元素の酸化物及び貴金属からなる群から選択される少なくとも一つであることが好ましい。 The catalyst of the present invention is characterized by comprising a powder comprising the oxide microcrystal particles of the present invention and a catalytically active species supported on the surface of the powder. The catalytically active species is preferably at least one selected from the group consisting of oxides of transition elements and noble metals.
なお、本発明の酸化物微結晶粒子からなる粉体の製造方法において有機物質（表面修飾剤分子）によって最表面が酸素イオン層により構成された活性な結晶面（蛍石構造の場合は（００１）面）が選択的に成長するようになる理由は必ずしも定かではないが、本発明者らは以下のように推察する。すなわち、先ず、酸化物結晶が成長する初期段階にその結晶の核が生成する。そして、その核に対して、有機物質（表面修飾剤分子）は表面エネルギーが高く不安定なため反応性の高い結晶面（蛍石構造の場合は（００１）面）と反応し、結晶表面が安定化される。一方、表面修飾剤分子と反応して安定化されている結晶面以外の結晶面には、引き続き酸化物の析出が進行してその面が消滅してしまう。その結果として、表面修飾剤分子で安定化された結晶面のみになると推察される。また、高温高圧の水熱合成法における反応場、特に超臨界水中では、表面修飾剤分子が均一に溶解し、効率良く酸化物の結晶面と接触して反応することが可能である。したがって、表面エネルギーが高く不安定な結晶面からなる酸化物微結晶粒子が高い割合で得られるようになると本発明者らは推察する。 In the method for producing a powder comprising fine oxide crystal particles of the present invention, an active crystal plane (001 in the case of a fluorite structure) having an outermost surface constituted by an oxygen ion layer by an organic substance (surface modifier molecule). The reason why the surface) is selectively grown is not necessarily clear, but the present inventors infer as follows. That is, first, the nucleus of the crystal is generated at the initial stage of growth of the oxide crystal. And the organic substance (surface modifier molecule) reacts with the crystal surface with high reactivity ((001) surface in the case of fluorite structure) because the surface energy is high and unstable with respect to the nucleus. Stabilized. On the other hand, on the crystal face other than the crystal face that has been stabilized by reacting with the surface modifier molecule, the precipitation of the oxide continues and the face disappears. As a result, it is surmised that only the crystal plane stabilized by the surface modifier molecule is obtained. Further, in the reaction field in the high-temperature and high-pressure hydrothermal synthesis method, particularly in supercritical water, the surface modifier molecules are uniformly dissolved and can react efficiently by contacting with the crystal plane of the oxide. Therefore, the present inventors speculate that oxide microcrystal particles having an unstable crystal plane with high surface energy can be obtained at a high rate.
また、本発明の酸化物微結晶粒子からなる粉体を用いて得た本発明の触媒によれば低温及び高温触媒活性が向上するようになる理由は必ずしも定かではないが、本発明者らは以下のように推察する。すなわち、酸化物の結晶構造には、一般に酸素が密に充填された結晶面と陽イオンが密に充填された結晶面、そしてそれらの両方が充填された結晶面が存在する。一般に、酸素が密に充填された結晶面が出た結晶粒子の形態は、熱力学的に不安定である。その理由は、結晶のチャージバランスの観点から、表面は酸素が半分だけ充填された構造となり、酸素イオンに対する構造的な制約は殆どない状態となる。例えば、蛍石構造の（００１）面及び該（００１）面と結晶学的に等価な結晶面のように、最表面の酸素イオンに対する陽イオンの配位数が２以下である結晶面では表面エネルギーが高い。この状態の酸素は、空気中の酸素分子よりも活性で、優先的に酸化物表面での酸化反応に寄与する。また、気相中の酸素分子が解離吸着しやすい酸素イオン空孔の対が容易にできるため、酸化反応に必要な酸素が容易に供給され高い酸化活性が得られる。この低温からの酸素の吸放出能は還元反応の活性化にも同時に寄与する。そのため、最表面が酸素イオン層により構成された活性な結晶面からなる酸化物微結晶粒子が５０質量％以上を占めている本発明の酸化物微結晶粒子からなる粉体を用いて得た本発明の触媒によれば、低温及び高温触媒活性が向上するようになると本発明者らは推察する。 Further, although the reason why the low-temperature and high-temperature catalytic activity is improved according to the catalyst of the present invention obtained using the powder comprising the oxide microcrystal particles of the present invention is not necessarily clear, the present inventors We infer as follows. That is, in the crystal structure of an oxide, there are generally a crystal plane that is densely filled with oxygen, a crystal face that is densely filled with cations, and a crystal face that is filled with both. In general, the morphology of crystal grains with crystal planes that are densely filled with oxygen is thermodynamically unstable. The reason is that from the viewpoint of the charge balance of the crystal, the surface has a structure in which only half of the oxygen is filled, and there is almost no structural restriction on oxygen ions. For example, a crystal plane having a cation coordination number of 2 or less with respect to oxygen ions on the outermost surface, such as a (001) plane having a fluorite structure and a crystal plane equivalent to the (001) plane, is a surface. Energy is high. The oxygen in this state is more active than oxygen molecules in the air and preferentially contributes to the oxidation reaction on the oxide surface. In addition, since oxygen ion vacancies can be easily formed in which oxygen molecules in the gas phase are easily dissociated and adsorbed, oxygen necessary for the oxidation reaction is easily supplied and high oxidation activity is obtained. This ability to absorb and release oxygen from a low temperature simultaneously contributes to the activation of the reduction reaction. Therefore, the book obtained by using the powder comprising the oxide microcrystal particles of the present invention in which the oxide microcrystal particles comprising the active crystal plane composed of the oxygen ion layer on the outermost surface account for 50% by mass or more. The inventors speculate that low and high temperature catalytic activity will be improved with the inventive catalyst.
本発明の酸化物微結晶粒子の製造方法によれば、活性な結晶面からなる酸化物微結晶粒子の比率を従来より大幅に向上させることが可能となる。そのため、本発明によれば、従来は得ることができなかった活性な結晶面からなる酸化物微結晶粒子が５０質量％以上を占める酸化物微結晶粒子の粉体を提供することが可能となり、さらにそれを用いて低温及び高温触媒活性に優れた触媒を提供することが可能となる。 According to the method for producing oxide microcrystal particles of the present invention, the ratio of oxide crystallite particles composed of active crystal faces can be significantly improved as compared with the conventional method. Therefore, according to the present invention, it is possible to provide a powder of oxide microcrystal particles in which the oxide crystallite particles composed of active crystal faces that could not be obtained conventionally account for 50% by mass or more, Furthermore, it becomes possible to provide a catalyst excellent in low-temperature and high-temperature catalytic activity using it.
以下、本発明をその好適な実施形態に即して詳細に説明する。 Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.
先ず、本発明の酸化物微結晶粒子からなる粉体について説明する。本発明の酸化物微結晶粒子からなる粉体は、最表面が酸素イオン層により構成された活性な結晶面からなる酸化物微結晶粒子が５０質量％以上を占めていることを特徴とするものである。 First, the powder comprising the oxide crystallite particles of the present invention will be described. The powder composed of oxide microcrystal particles of the present invention is characterized in that the oxide microcrystal particles composed of an active crystal plane whose outermost surface is constituted by an oxygen ion layer account for 50% by mass or more. It is.
本発明にかかる酸化物としては、微結晶粒子を構成することが可能なものであればよく、特に限定されない。このような酸化物を構成する金属元素としては、長周期型周期表で第ＩＩＩＢ族のホウ素（Ｂ）〜第ＩＶＢ族のケイ素（Ｓｉ）〜第ＶＢ族のヒ素（Ａｓ）〜第ＶＩＢ族のテルル（Ｔｅ）の線を境界としてその線上にある元素並びにその境界より長周期型周期表において左側ないし下側にあるものが挙げられ、例えば、第ＶＩＩＩ族の元素ではＦｅ、Ｃｏ、Ｎｉ、Ｒｕ、Ｒｈ、Ｐｄ、Ｏｓ、Ｉｒ、Ｐｔ等、第ＩＢ族の元素ではＣｕ、Ａｇ、Ａｕ等、第ＩＩＢ族の元素ではＺｎ、Ｃｄ、Ｈｇ等、第ＩＩＩＢ族の元素ではＢ、Ａｌ、Ｇａ、Ｉｎ、Ｔｌ等、第ＩＶＢ族の元素ではＳｉ、Ｇｅ、Ｓｎ、Ｐｂ等、第ＶＢ族の元素ではＡｓ、Ｓｂ、Ｂｉ等、第ＶＩＢ族の元素ではＴｅ、Ｐｏ等、そして第ＩＡ〜ＶＩＩＡ族の元素が挙げられる。 The oxide according to the present invention is not particularly limited as long as it can form microcrystalline particles. As a metal element constituting such an oxide, Group IIIB boron (B) to Group IVB silicon (Si) to Group VB arsenic (As) to Group VIB in the long-period periodic table. Examples include elements on the line with the line of tellurium (Te) as well as those on the left or lower side of the long-period periodic table from the boundary. For example, elements of Group VIII include Fe, Co, Ni, Ru , Rh, Pd, Os, Ir, Pt, etc., group IB elements such as Cu, Ag, Au, etc., group IIB elements such as Zn, Cd, Hg, etc., group IIIB elements such as B, Al, Ga, In, Tl, etc., Group IVB elements such as Si, Ge, Sn, Pb, etc., Group VB elements As, Sb, Bi, etc., Group VIB elements such as Te, Po, etc., and Groups IA to VIIA These elements are mentioned.
したがって、本発明にかかる金属酸化物としては、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ａｇ、Ａｕ、Ｚｎ、Ｃｄ、Ｈｇ、Ａｌ、Ｇａ、Ｉｎ、Ｔｌ、Ｓｉ、Ｇｅ、Ｓｎ、Ｐｂ、Ｔｉ、Ｚｒ、Ｍｎ、Ｅｕ、Ｙ、Ｎｂ、Ｃｅ、Ｂａ等の酸化物が挙げられ、例えば、ＳｉＯ２、ＴｉＯ２、ＺｎＯ２、ＳｎＯ２、Ａｌ２Ｏ３、ＭｎＯ２、ＮｉＯ、Ｅｕ２Ｏ３、Ｙ２Ｏ３、Ｎｂ２Ｏ３、ＩｎＯ、ＺｎＯ、Ｆｅ２Ｏ３、Ｆｅ３Ｏ４、Ｃｏ３Ｏ４、ＺｒＯ２、ＣｅＯ２、ＢａＯ・６Ｆｅ２Ｏ３、Ａｌ５（Ｙ＋Ｔｂ）３Ｏ１２、ＢａＴｉＯ３、ＬｉＣｏＯ２、ＬｉＭｎ２Ｏ４、Ｋ２Ｏ・６ＴｉＯ２が挙げられる。 Therefore, the metal oxide according to the present invention includes Fe, Co, Ni, Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Ti, Zr, Examples include oxides such as Mn, Eu, Y, Nb, Ce, and Ba. For example, SiO 2 , TiO 2 , ZnO 2 , SnO 2 , Al 2 O 3 , MnO 2 , NiO, Eu 2 O 3 , Y 2. O 3 , Nb 2 O 3 , InO, ZnO, Fe 2 O 3 , Fe 3 O 4 , Co 3 O 4 , ZrO 2 , CeO 2 , BaO · 6Fe 2 O 3 , Al 5 (Y + Tb) 3 O 12 , BaTiO 3 3 , LiCoO 2 , LiMn 2 O 4 , K 2 O.6TiO 2 .
また、酸化物を構成する陽イオン（金属元素）の原子価が複数存在する場合は、最表面の酸素は容易に脱離するため、結晶面の活性がより向上して触媒活性が優れた触媒が得られるようになる傾向にあることから、本発明にかかる酸化物を構成する陽イオンが複数の原子価を取り得る元素の陽イオンであることが好ましく、中でも人体への影響が小さい傾向にあるという観点からＣｅ、Ｐｒ、Ｆｅ、Ｎｉ、Ｃｕ、Ｖ及びＣｏからなる群から選択される少なくとも一つの元素の陽イオンであることがより好ましく、Ｃｅの陽イオンが特に好ましい。 In addition, when there are multiple valences of cations (metal elements) constituting the oxide, oxygen on the outermost surface is easily desorbed, so that the activity of the crystal plane is further improved and the catalyst has excellent catalytic activity. Therefore, it is preferable that the cation constituting the oxide according to the present invention is a cation of an element that can take a plurality of valences, and in particular, the influence on the human body tends to be small. From a certain viewpoint, it is more preferably a cation of at least one element selected from the group consisting of Ce, Pr, Fe, Ni, Cu, V, and Co, and a cation of Ce is particularly preferable.
さらに、本発明にかかる酸化物を構成する陽イオンが、Ｃｅの陽イオンと、Ｃｅ以外の希土類元素からなる群から選択される少なくとも一つの第二成分の陽イオンとを含有するものであると、陽イオンの体積拡散が阻害されるため高温でも結晶の形態を安定に保ち易い傾向にあることから好ましく、このような第二成分がＬａであると、特にイオン半径が大きいことから結晶を安定化する機能が高くなる傾向にあることからより好ましい。また、このような第二成分を含有する場合、その含有率は、Ｃｅと前記第二成分との合計量を基準として３〜２０モル％であることが好ましい。第二成分の含有率が上記下限未満ではその添加効果が十分に得られなくなる傾向にあり、他方、上記上限を超えるとＣｅの原子価変化の作用が十分でなくなり酸素の吸脱着性が低下する傾向にある。 Furthermore, the cation constituting the oxide according to the present invention contains a cation of Ce and at least one second component cation selected from the group consisting of rare earth elements other than Ce. It is preferable because it tends to keep the crystal form stable even at high temperatures because the volume diffusion of the cation is hindered, and when such a second component is La, the crystal is particularly stable because the ionic radius is large. It is more preferable because the function to be converted tends to be high. Moreover, when such a 2nd component is contained, it is preferable that the content rate is 3-20 mol% on the basis of the total amount of Ce and said 2nd component. If the content of the second component is less than the above lower limit, the effect of addition tends not to be sufficiently obtained. On the other hand, if the content exceeds the upper limit, the effect of changing the valence of Ce is insufficient and the oxygen adsorption / desorption is reduced. There is a tendency.
本発明の粉体は、上記酸化物の微結晶粒子からなるものである。本発明にかかる微結晶粒子としては、その平均粒径が１μｍ程度以下のサイズのものが挙げられるが、好ましくはナノ粒子である。このようなナノ粒子としては、一般的にはその平均粒径が２００ｎｍ以下のサイズのものが挙げられ、平均粒径が１００ｎｍ以下のサイズのものが好ましく、平均粒径が５０ｎｍ以下のサイズのものがより好ましい。また、本発明にかかる微結晶粒子の形状としては、擬似立方体粒子、平板状円形粒子、平板状細長粒子、擬似直方体粒子等が挙げられ、中でも擬似立方体粒子が好ましい。なお、本発明にかかる粉体は、粒子サイズや形状が均一な微結晶粒子の集合体であることが好ましいが、粒子サイズや形状が異なる微結晶粒子の混合体であってもよい。 The powder of the present invention is composed of fine crystal particles of the above oxide. Examples of the microcrystalline particles according to the present invention include those having an average particle size of about 1 μm or less, and preferably nanoparticles. Such nanoparticles generally include those having an average particle size of 200 nm or less, preferably those having an average particle size of 100 nm or less, and those having an average particle size of 50 nm or less. Is more preferable. Examples of the shape of the microcrystalline particles according to the present invention include pseudo cubic particles, tabular circular particles, tabular elongated particles, and pseudo rectangular parallelepiped particles. Among them, pseudo cubic particles are preferable. The powder according to the present invention is preferably an aggregate of microcrystalline particles having a uniform particle size and shape, but may be a mixture of microcrystalline particles having different particle sizes and shapes.
本発明においては、上記酸化物微結晶粒子からなる粉体において、最表面が酸素イオン層により構成された活性な結晶面からなる酸化物微結晶粒子が５０質量％以上を占めていることが必要であり、７０質量％以上を占めていることが好ましく、８０質量％以上を占めていることがより好ましく、９５質量％以上を占めていることが特に好ましい。このように活性な結晶面からなる酸化物微結晶粒子が５０質量％以上を占めている粉体は、後述する本発明の製造方法によってはじめて得られるようになったものであり、このような粉体を用いることによって低温及び高温触媒活性が飛躍的に向上した触媒が得られるようになる。 In the present invention, in the powder composed of the oxide microcrystal particles, it is necessary that the oxide microcrystal particles composed of an active crystal plane whose outermost surface is constituted by an oxygen ion layer occupy 50% by mass or more. It is preferable that it occupies 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 95% by mass or more. The powder in which the oxide crystallite particles composed of active crystal faces account for 50% by mass or more is obtained for the first time by the production method of the present invention described later. By using the body, a catalyst having dramatically improved low-temperature and high-temperature catalytic activity can be obtained.
なお、「最表面が酸素イオン層により構成されている」とは、酸化物微結晶粒子の全ての表面に酸素が密に充填された結晶面が出ている形態を言うが、最表面に露出している全てのサイトが酸素イオンサイトである必要はなく、最表面に露出しているサイトのうちの８０％以上が酸素イオンサイトであればよく、９０％以上が酸素イオンサイトであることがより好ましく、１００％が酸素イオンサイトであることが特に好ましい。このように本発明にかかる酸化物微結晶粒子の表面は酸素が密に充填された結晶面により構成されているが、最表面に露出した酸素イオンは結晶のチャージバランスの観点から、実際にその表面に充填されている酸素イオンの数は結晶学的に配置可能な酸素イオンの数の４０〜９０ａｔ％程度（特に好ましくは５０ａｔ％程度）となっている構造となる。そのため、酸素イオンに対する構造的な制約は殆どない状態となる。したがって、このような状態の酸素イオンは空気中の酸素分子よりも活性であり、このような酸素イオン層により最表面が構成された結晶面は活性となる。そして、活性な酸素イオンは、優先的に酸化物表面での酸化反応に寄与する。また、気相中の酸素分子が解離吸着しやすい酸素イオン空孔の対が容易にできるため、酸化反応に必要な酸素が容易に供給され高い酸化活性が得られる。この低温からの酸素の吸放出能は還元反応の活性化にも同時に寄与するようになる。 Note that “the outermost surface is composed of an oxygen ion layer” refers to a form in which all surfaces of the oxide microcrystalline particles have crystal planes that are densely filled with oxygen, but are exposed on the outermost surface. It is not necessary that all the sites are oxygen ion sites, but 80% or more of the sites exposed on the outermost surface may be oxygen ion sites, and 90% or more may be oxygen ion sites. More preferably, 100% is particularly preferably an oxygen ion site. As described above, the surface of the oxide microcrystal particle according to the present invention is composed of a crystal plane in which oxygen is densely packed, but the oxygen ions exposed on the outermost surface are actually the same from the viewpoint of the charge balance of the crystal. The number of oxygen ions filled on the surface is about 40 to 90 at% (particularly preferably about 50 at%) of the number of oxygen ions that can be arranged crystallographically. Therefore, there is almost no structural restriction on oxygen ions. Therefore, oxygen ions in such a state are more active than oxygen molecules in the air, and a crystal plane whose outermost surface is constituted by such an oxygen ion layer becomes active. Active oxygen ions preferentially contribute to the oxidation reaction on the oxide surface. In addition, since oxygen ion vacancies can be easily formed in which oxygen molecules in the gas phase are easily dissociated and adsorbed, oxygen necessary for the oxidation reaction is easily supplied and high oxidation activity is obtained. This ability to absorb and release oxygen from a low temperature simultaneously contributes to the activation of the reduction reaction.
本発明において、前記活性な結晶面が以下の（i）〜（iii）のうちの少なくとも一つの条件を満たしていることが好ましい。
（i）前記活性な結晶面を構成する最表面の酸素イオンに対する陽イオンの配位数が２以下であること。
（ii）前記活性な結晶面が、表面エネルギーが高く不安定な結晶面であること。
（iii）前記活性な結晶面からなる酸化物微結晶粒子がホタル石構造を有しており、前記活性な結晶面が（００１）面及びその（００１）面と結晶学的に等価な結晶面であること。
In the present invention, the active crystal plane preferably satisfies at least one of the following conditions (i) to (iii).
(I) The coordination number of cations with respect to oxygen ions on the outermost surface constituting the active crystal plane is 2 or less.
(Ii) The active crystal plane is an unstable crystal plane with high surface energy.
(Iii) The oxide microcrystalline particles comprising the active crystal plane have a fluorite structure, and the active crystal plane is a crystal plane that is crystallographically equivalent to the (001) plane and the (001) plane. Be.
なお、活性な結晶面を構成する最表面の酸素イオン、すなわち不安定な酸素は、最近接位置にある陽イオンの配位数が２以下と小さい。例えば、セリア微結晶粒子の場合、（００１）面及びその（００１）面と結晶学的に等価な結晶面における最表面酸素イオンのＣｅイオン配位数は２であり、一方、（１１０）面や（１１１）面における最表面酸素イオンのＣｅイオン配位数は４である。 Note that the outermost oxygen ion constituting the active crystal plane, that is, unstable oxygen, has a coordination number of the cation at the nearest position as small as 2 or less. For example, in the case of ceria microcrystalline particles, the Ce ion coordination number of the outermost surface oxygen ion in the (001) plane and a crystallographically equivalent crystal plane to the (001) plane is 2, while the (110) plane The Ce ion coordination number of the outermost surface oxygen ion in the (111) plane is 4.
本発明にかかる酸化物微結晶粒子の粒径及び形状は前述の通りであるが、上述の活性な結晶面からなる酸化物微結晶粒子の平均粒径は２ｎｍ〜３０ｎｍの範囲内であることが好ましい。この平均粒径が前記下限未満では耐熱性が不十分となり５００℃未満の加熱によって焼結して別の形状に変化してしまう傾向にあり、他方、上記上限を超えると触媒として用いるためには比表面積が不十分となる傾向にある。また、本発明にかかる活性な結晶面からなる酸化物微結晶粒子としては、粒子間の空隙を十分に持つ二次粒子形成のため、及び耐熱性を高くするという観点から、単分散ナノ結晶粒子であることが好ましく、単結晶の単分散ナノ結晶粒子であることが特に好ましい。 The particle size and shape of the oxide microcrystal particles according to the present invention are as described above, but the average particle size of the oxide microcrystal particles composed of the above active crystal plane is in the range of 2 nm to 30 nm. preferable. If the average particle size is less than the lower limit, the heat resistance becomes insufficient and the powder tends to sinter and change to another shape by heating at less than 500 ° C. The specific surface area tends to be insufficient. In addition, as the oxide microcrystal particles having an active crystal face according to the present invention, monodisperse nanocrystal particles are used for forming secondary particles having sufficient voids between the particles and from the viewpoint of increasing heat resistance. And monodisperse monodisperse nanocrystal particles are particularly preferred.
なお、このような酸化物微結晶粒子の結晶面は、ＨＲ−ＴＥＭ（高分解能透過型電子顕微鏡）、電子線回折法等を用いて解析することができる。また、結晶の組成は、ＥＤＸ分析等によって確認することができ、粒子の粒径は、ＴＥＭ、吸着法、光散乱法、ＳＡＸＳ等により測定することができる。なお、吸着法とは、Ｎ２吸着等によりＢＥＴ比表面積を評価する方法である。 Note that the crystal plane of such oxide microcrystalline particles can be analyzed using HR-TEM (High Resolution Transmission Electron Microscope), electron diffraction method or the like. The crystal composition can be confirmed by EDX analysis or the like, and the particle size of the particles can be measured by TEM, adsorption method, light scattering method, SAXS or the like. The adsorption method is a method for evaluating the BET specific surface area by N 2 adsorption or the like.
次に、本発明の酸化物微結晶粒子からなる粉体の製造方法について説明する。本発明においては、高温高圧の水熱合成法における反応場において、酸化物微結晶粒子を構成すべき陽イオンの水酸化物から有機物質の共存下で酸化物微結晶粒子を合成する。 Next, the manufacturing method of the powder which consists of oxide microcrystal particle | grains of this invention is demonstrated. In the present invention, oxide microcrystal particles are synthesized in the presence of an organic substance from a cation hydroxide that constitutes oxide microcrystal particles in a reaction field in a high-temperature and high-pressure hydrothermal synthesis method.
本発明にかかる高温高圧の水熱合成法における反応場としては、亜臨界又は超臨界条件にある溶媒（水、或いは水と有機溶媒との混合溶媒）が好適に採用され、そのような反応場の温度としては３５０〜４５０℃程度が好ましく、圧力（純水と仮定）としては１６０〜５００ｂａｒ程度（特に好ましくは３００〜５００ｂａｒ）が好ましい。このような反応場とすることによって、独特の反応環境が提供され、後述する特定の有機物質によって酸化物微結晶の表面が有機修飾されることとの相乗作用によって形成される結晶面が規制され、驚くべきことに前述の活性な結晶面を有する酸化物微結晶粒子が選択的に得られるようになる。 As the reaction field in the high-temperature and high-pressure hydrothermal synthesis method according to the present invention, a solvent in a subcritical or supercritical condition (water or a mixed solvent of water and an organic solvent) is preferably employed. Is preferably about 350 to 450 ° C., and the pressure (assumed to be pure water) is preferably about 160 to 500 bar (particularly preferably 300 to 500 bar). By using such a reaction field, a unique reaction environment is provided, and the crystal plane formed by the synergistic action of organic modification of the surface of the oxide microcrystal by a specific organic substance described later is regulated. Surprisingly, it becomes possible to selectively obtain oxide microcrystalline particles having the above-mentioned active crystal face.
このような反応場を形成する反応装置としては、高温高圧の条件を達成できる装置であればよく、特に限定されず、例えば、回分式装置、流通式装置のいずれも使用することができる。 The reaction apparatus for forming such a reaction field is not particularly limited as long as it can achieve conditions of high temperature and high pressure, and for example, either a batch type apparatus or a flow type apparatus can be used.
本発明においては、前述の酸化物微結晶粒子を構成すべき陽イオン（金属元素）の水酸化物を原料として用いる必要がある。作用機序は定かではないが、このような陽イオン（金属元素）の水酸化物を用いることによって、従来のように陽イオン（金属元素）の塩（硝酸塩等）を用いた場合より、生成される粉体における前述の活性な結晶面を有する酸化物微結晶粒子の比率が飛躍的に向上し、前記本発明の粉体が得られるようになる。なお、陽イオン（金属元素）の水酸化物を得る方法は特に制限されないが、例えば、陽イオン（金属元素）の塩を含有する溶液をアルカリ（水酸化カリウム、水酸化ナトリウム等）で中和し、得られた沈殿を必要に応じて洗浄した後に水に再分散させることによって得られる。 In the present invention, it is necessary to use, as a raw material, a hydroxide of a cation (metal element) that constitutes the aforementioned oxide microcrystal particles. The mechanism of action is not clear, but by using such a cation (metal element) hydroxide, it can be produced compared to the conventional case of using a cation (metal element) salt (nitrate, etc.). The ratio of the oxide fine crystal particles having the above active crystal face in the powder to be greatly improved, and the powder of the present invention can be obtained. The method for obtaining a cation (metal element) hydroxide is not particularly limited. For example, a solution containing a cation (metal element) salt is neutralized with an alkali (potassium hydroxide, sodium hydroxide, etc.). The resulting precipitate is washed as necessary and then redispersed in water.
本発明にかかる有機物質としては、酸化物微結晶粒子の表面に炭化水素を強結合せしめることのできるものであればよく、特に限定されず、例えば、エーテル結合、エステル結合、Ｎ原子を介した結合、Ｓ原子を介した結合、金属−Ｃ−の結合、金属−Ｃ＝の結合、金属−（Ｃ＝Ｏ）−の結合等の強結合を形成することができる各種の有機物質が挙げられる。結合される炭化水素としては、その炭素数は特に限定されず、炭素数が１や２のものも使用できるが、炭素数が３以上の鎖を有する長鎖炭化水素が好ましく、例えば、炭素数３〜２０の直鎖又は分岐鎖、あるいは環状の炭化水素等が挙げられる。また、このような炭化水素は、置換されていてもよいし、非置換のものであってもよい。 The organic substance according to the present invention is not particularly limited as long as it can cause hydrocarbons to be strongly bonded to the surface of the oxide microcrystalline particles, and examples thereof include ether bonds, ester bonds, and N atoms. Various organic substances that can form a strong bond such as a bond, a bond through an S atom, a bond of metal-C-, a bond of metal-C =, a bond of metal- (C = O)-, and the like. . As the hydrocarbon to be bonded, the number of carbon atoms is not particularly limited, and those having 1 or 2 carbon atoms can be used, but long-chain hydrocarbons having a chain having 3 or more carbon atoms are preferable. Examples thereof include 3 to 20 linear or branched chain or cyclic hydrocarbons. Moreover, such hydrocarbons may be substituted or unsubstituted.
このような有機物質としては、生成される粉体における活性な結晶面を有する酸化物微結晶粒子の比率がより向上するという観点から炭素数６〜１０のカルボン酸が用いられ、ヘキサン酸、デカン酸が特に好ましい。 Such organic material, the carboxylic acid having 6 to 10 carbon atoms is used from the viewpoint of the ratio of the oxide fine crystal grains say you improved with active crystal faces in live powder made, hexane Acid and decanoic acid are particularly preferred.
本発明の製造方法においては、前述の反応場に前記陽イオンの水酸化物と前記有機物質とを共存せしめ、酸化物微結晶粒子を生成させる。その際の前記陽イオンの水酸化物及び前記有機物質の配合量は特に制限されないが、陽イオンの水酸化物と有機物質との比（モル比）が５：１〜１：１０であることが好ましく、１：１〜１：５であることがより好ましい。陽イオンの水酸化物に対する有機物質の比率が上記下限未満では有機物質の表面修飾作用が不十分で生成する結晶の形態が不規則且つ粗大となる傾向にあり、他方、上記上限を超えると得られる結晶の収率が低くなり且つ結晶のサイズが小さ過ぎる傾向にある。また、反応溶液中の前記陽イオンの水酸化物の濃度も特に制限されないが、０．０１〜１．０モル／ｌであることが好ましく、０．１〜０．２モル／ｌであることがより好ましい。さらに、反応時間も特に制限されないが、一般的には０．０１〜２０分間程度の反応時間が採用される。 In the production method of the present invention, the cation hydroxide and the organic substance are allowed to coexist in the reaction field described above to produce oxide microcrystalline particles. The mixing amount of the cation hydroxide and the organic substance is not particularly limited, but the ratio (molar ratio) between the cation hydroxide and the organic substance is 5: 1 to 1:10. Is preferable, and 1: 1 to 1: 5 is more preferable. If the ratio of the organic substance to the cation hydroxide is less than the above lower limit, the surface modification action of the organic substance is insufficient, and the form of crystals formed tends to be irregular and coarse. The yield of the resulting crystals is low and the size of the crystals tends to be too small. The concentration of the cation hydroxide in the reaction solution is not particularly limited, but is preferably 0.01 to 1.0 mol / l, and preferably 0.1 to 0.2 mol / l. Is more preferable. Furthermore, the reaction time is not particularly limited, but generally a reaction time of about 0.01 to 20 minutes is employed.
本発明の製造方法においては、上記の反応によって生成した酸化物微結晶粒子を、通常は室温程度に冷却した後に、遠心分離、メンブランフィルタ等によって分離し、必要に応じて水、エタノール等によって洗浄して前記本発明の粉体が得られる。 In the production method of the present invention, the oxide microcrystal particles produced by the above reaction are usually cooled to about room temperature, separated by centrifugation, membrane filter, etc., and washed with water, ethanol, etc. as necessary. Thus, the powder of the present invention is obtained.
次に、本発明の触媒について説明する。本発明の触媒は、前記本発明の酸化物微結晶粒子からなる粉体と、前記粉体の表面に担持された触媒活性種とを備えることを特徴とするものである。 Next, the catalyst of the present invention will be described. The catalyst of the present invention comprises a powder comprising the oxide microcrystal particles of the present invention, and a catalytically active species supported on the surface of the powder.
本発明にかかる触媒活性種としては、目的とする触媒活性に寄与する物質であればよく、特に制限されないが、遷移元素の酸化物及び貴金属からなる群から選択される少なくとも一つの元素が挙げられる。このような貴金属としては、Ｐｔ、Ｐｄ、Ｒｈ、Ｒｕ、Ｉｒ、Ｏｓ、Ａｕ、Ａｇ等が挙げられ、中でも触媒活性の観点から白金族元素（Ｐｔ、Ｐｄ、Ｒｈ、Ｒｕ、Ｉｒ、Ｏｓ）が好ましく、Ｐｔが特に好ましい。また、遷移元素の酸化物としては、担持する対象となる酸化物微結晶粒子を構成する酸化物とは相違するものであればよく、Ｆｅ、Ｃｕ、Ｃｏ、Ｎｉ、Ｚｒ、Ｔｉ、Ｚｎ、Ｖ、Ｗ、Ｍｏ、Ｃｒ、Ｎｂ、Ｓｎ、Ｍｎ、Ｓｍ、Ｅｕ、Ｔｂ、Ｙｂ等の酸化物が挙げられ、中でも触媒活性の観点から酸化鉄、酸化銅が好ましく、酸化鉄が特に好ましい。なお、遷移元素の酸化物は、単独の金属酸化物であっても、複数の金属酸化物からなる複合金属酸化物であってもよい。 The catalytically active species according to the present invention is not particularly limited as long as it is a substance that contributes to the target catalytic activity, and includes at least one element selected from the group consisting of oxides of transition elements and noble metals. . Examples of such noble metals include Pt, Pd, Rh, Ru, Ir, Os, Au, Ag, and the like. Among them, platinum group elements (Pt, Pd, Rh, Ru, Ir, Os) are preferable from the viewpoint of catalytic activity. Pt is preferable and Pt is particularly preferable. The oxide of the transition element may be any oxide that is different from the oxide that constitutes the oxide microcrystal particles to be supported. Fe, Cu, Co, Ni, Zr, Ti, Zn, V , W, Mo, Cr, Nb, Sn, Mn, Sm, Eu, Tb, Yb, and the like. Among them, iron oxide and copper oxide are preferable from the viewpoint of catalytic activity, and iron oxide is particularly preferable. The transition element oxide may be a single metal oxide or a complex metal oxide composed of a plurality of metal oxides.
本発明の触媒において前記粉体に担持される触媒活性種の量も特に制限されないが、担持される前記粉体１００質量部に対して触媒活性種の量が０．１〜１０質量部程度であることが好ましい。 The amount of the catalytically active species supported on the powder in the catalyst of the present invention is not particularly limited, but the amount of the catalytically active species is about 0.1 to 10 parts by mass with respect to 100 parts by mass of the supported powder. Preferably there is.
また、前記粉体に触媒活性種を担持せしめる具体的な方法も特に制限されず、例えば、貴金属を担持する場合は、貴金属の塩（硝酸塩、塩化物、酢酸塩等）又は錯体を含有する溶液に前記粉体を接触せしめ、更に必要に応じて還元処理及び／又は焼成処理を施すといった方法が適宜採用される。また、遷移元素の酸化物を担持する場合は、遷移元素の塩（硝酸塩、塩化物、酢酸塩等）又は錯体を含有する溶液に前記粉体を接触せしめ、更に必要に応じて酸化処理及び／又は焼成処理を施すといった方法が適宜採用される。 Further, a specific method for supporting the catalytically active species on the powder is not particularly limited. For example, when supporting a noble metal, a solution containing a noble metal salt (nitrate, chloride, acetate, etc.) or a complex. A method in which the powder is brought into contact with the substrate and further subjected to a reduction treatment and / or a firing treatment as necessary is appropriately employed. In the case of supporting an oxide of a transition element, the powder is brought into contact with a solution containing a transition element salt (nitrate, chloride, acetate, etc.) or a complex, and if necessary, oxidation treatment and / or Or the method of giving a baking process is employ | adopted suitably.
本発明の触媒は、粉体のまま、或いはペレット等の所定の形状に成形して使用してもよいが、触媒用基材に担持して用いてもよい。このような基材は特に制限されず、触媒の用途等に応じて適宜選択されるが、排ガス浄化用触媒等として用いる場合は、モノリス担体基材（ハニカムフィルタ、高密度ハニカム等）、フォームフィルタ基材、ペレット状基材、プレート状基材等が好適に採用される。また、このような基材の材質も特に制限されないが、排ガス浄化用触媒等として用いる場合は、コージエライト、炭化ケイ素、ムライト等のセラミックスからなる基材や、クロム及びアルミニウムを含むステンレススチール等の金属からなる基材が好適に採用される。 The catalyst of the present invention may be used in the form of powder or formed into a predetermined shape such as pellets, but may be used by being supported on a catalyst substrate. Such a substrate is not particularly limited and is appropriately selected according to the application of the catalyst, etc., but when used as an exhaust gas purification catalyst or the like, a monolith carrier substrate (honeycomb filter, high density honeycomb, etc.), foam filter A substrate, a pellet-shaped substrate, a plate-shaped substrate and the like are preferably employed. In addition, the material of such a base material is not particularly limited, but when used as an exhaust gas purification catalyst, a base material made of ceramics such as cordierite, silicon carbide, mullite, or a metal such as stainless steel containing chromium and aluminum. The base material which consists of is employ | adopted suitably.
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.
（実施例１）
内容積５ｃｍ３の密閉型反応容器（管型オートクレーブ）に、０．０３モル／ｌの水酸化セリウム懸濁液４．４ｍｌとヘキサン酸０．１ｍｌを仕込み、２００℃に設定した加熱炉に反応容器を入れて加熱した。昇温には１．５分を要し、２０分間反応させた後、室温まで冷却し、得られた粉体を遠心分離して水、エタノールで洗浄した。
Example 1
A closed reaction vessel (tubular autoclave) with an internal volume of 5 cm 3 was charged with 4.4 ml of 0.03 mol / l cerium hydroxide suspension and 0.1 ml of hexanoic acid, and reacted in a heating furnace set at 200 ° C. The container was placed and heated. It took 1.5 minutes to raise the temperature. After reacting for 20 minutes, the mixture was cooled to room temperature, and the resulting powder was centrifuged and washed with water and ethanol.
ＨＲ−ＴＥＭ（高分解能透過型電子顕微鏡）を用いて生成した粉体を構成する微粒子の形態を観察したところ、図１に示す擬似立方体粒子（平均粒径：７ｎｍ）、図２に示す平板状円形小粒子（平均粒径：６ｎｍ）、図３に示す平板状細長粒子（平均長さ：１０ｎｍ）、図４に示す平板状円形大粒子（平均粒径：１０ｎｍ）が存在しており、それらはカッコ内に示す平均粒径又は平均長さを有していた。これらの結晶についてＥＤＸ分析を行ったところ、いずれもセリア（ＣｅＯ２）の結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 Observation of the morphology of the fine particles constituting the powder produced using HR-TEM (high resolution transmission electron microscope) revealed a pseudo cubic particle (average particle size: 7 nm) shown in FIG. 1 and a flat plate shape shown in FIG. There are circular small particles (average particle size: 6 nm), tabular elongated particles (average length: 10 nm) shown in FIG. 3, and tabular large circular particles (average particle size: 10 nm) shown in FIG. Had the average particle size or average length shown in parentheses. When EDX analysis was performed on these crystals, all were ceria (CeO 2 ) crystals, and at least pseudo-cubic particles were confirmed to be monodisperse nanocrystals composed of single crystals.
これらの結晶について格子像写真の格子面とその角度から解析を行ったところ、円形小粒子、円形大粒子及び細長粒子においては、面間隔がｄ＝３．１Åの（１１１）面が約７０°で交差することから、（１１０）面からなるものであることが確認された。また、電子線の透過のしやすさから厚さが幅に比べて非常に薄いことがわかり、平板状の粒子であることが確認された。一方、擬似立方体粒子においては、（２００）面と（０２０）面が直角に交わっていることから、（００１）面およびそれと等価な面からなる立方体状の粒子であることが確認された。 When these crystals were analyzed from the lattice plane of the lattice image photograph and the angle thereof, in the case of small circular particles, large circular particles, and long and narrow particles, the (111) plane with an interplanar spacing of d = 3.1 mm was about 70 °. It was confirmed that it consists of (110) planes. Further, it was found that the thickness was very thin compared to the width from the ease of transmission of electron beams, and it was confirmed that the particles were flat. On the other hand, since the (200) plane and the (020) plane intersect at right angles, the pseudo cubic particle was confirmed to be a cubic particle composed of the (001) plane and an equivalent plane.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約７０％であった。なお、擬似立方体粒子は、他の形状の粒子よりも明らかに１個当りの質量が大きいと見積られるが、仮に同じ質量と仮定しても７０質量％以上は擬似立方体粒子が得られたことが分かった。したがって、最表面が酸素イオン層により構成された活性な結晶面からなるセリア微結晶粒子が５０質量％以上を占めている従来は得ることができなかった粉体であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about 70%. In addition, although it is estimated that the pseudo cubic particles have a mass per particle that is clearly larger than those of other shaped particles, it is assumed that even if the same mass is assumed, pseudo cubic particles are obtained for 70% by mass or more. I understood. Therefore, it was confirmed that the ceria microcrystal particles having an active crystal face composed of an oxygen ion layer on the outermost surface accounted for 50% by mass or more and could not be obtained conventionally.
（実施例２）
加熱炉の温度を４００℃に設定し、さらに水酸化セリウム懸濁液の量を２．５ｍｌ、ヘキサン酸の量を０．０５７ｍｌとした以外は実施例１と同様にして粉体を得た。
(Example 2)
A powder was obtained in the same manner as in Example 1 except that the temperature of the heating furnace was set to 400 ° C., the amount of the cerium hydroxide suspension was 2.5 ml, and the amount of hexanoic acid was 0.057 ml.
生成した粉体を構成する微粒子の形態を実施例１と同様にＨＲ−ＴＥＭ観察及びＥＤＸ分析したところ、図５〜図６に示すように、擬似立方体粒子（平均粒径：６ｎｍ）、平板状円形小粒子（平均粒径：４ｎｍ）、平板状円形大粒子（平均粒径：１０ｎｍ）が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 The form of fine particles constituting the produced powder was observed by HR-TEM and EDX analysis in the same manner as in Example 1. As shown in FIGS. 5 to 6, pseudo cubic particles (average particle size: 6 nm), flat plate shape There are small circular particles (average particle size: 4 nm) and tabular large circular particles (average particle size: 10 nm), both of which are ceria crystals, and at least pseudo-cubic particles are monodisperse nanocrystals composed of single crystals. It was confirmed that.
これらの結晶について格子像写真の格子面とその角度から解析を行ったところ、実施例１で得られたものと同様に、円形小粒子及び円形大粒子は（１１０）面からなる平板状の粒子であり、擬似立方体粒子は（００１）面およびそれと等価な面からなる立方体状の粒子であることが確認された。 When these crystals were analyzed from the lattice plane of the lattice image photograph and the angle thereof, as in the case of Example 1, circular small particles and circular large particles are tabular grains having (110) planes. Thus, it was confirmed that the pseudo cubic particle is a cubic particle having a (001) plane and a plane equivalent thereto.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約８０質量％であり、最表面が酸素イオン層により構成された活性な結晶面からなるセリア微結晶粒子が５０質量％以上を占めている従来は得ることができなかった粉体であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It is 80% by mass, and it is confirmed that it is a powder that could not be obtained in the past, with ceria microcrystalline particles comprising active crystal planes composed of an oxygen ion layer on the outermost surface accounting for 50% by mass or more. It was done.
（比較例１）
内容積５ｃｍ３の密閉型反応容器に、０．１モル／ｌの硝酸セリウム水溶液２．５ｍｌとデカン酸０．０１ｍｌを仕込み、３５０℃に設定した加熱炉に反応容器を入れて加熱した。昇温には１．５分を要し、２０分間反応させた後、室温まで冷却し、得られた粉体をメンブランフィルターで分離して水、エタノールで洗浄した。
(Comparative Example 1)
A sealed reaction vessel having an internal volume of 5 cm 3 was charged with 2.5 ml of a 0.1 mol / l cerium nitrate aqueous solution and 0.01 ml of decanoic acid, and the reaction vessel was placed in a heating furnace set at 350 ° C. and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.
生成した粉体を構成する微粒子の形態を実施例１と同様にＨＲ−ＴＥＭ観察及びＥＤＸ分析したところ、図７〜図８に示すように、平均粒径が約１０ｎｍの平板状の円形小粒子のみが存在しており、いずれもセリアの結晶であることが確認された。 The shape of the fine particles constituting the produced powder was observed by HR-TEM and EDX analysis in the same manner as in Example 1. As shown in FIGS. 7 to 8, flat circular small particles having an average particle diameter of about 10 nm were obtained. It was confirmed that all were ceria crystals.
これらの結晶について格子像写真の格子面とその角度から解析を行ったところ、面間隔がｄ＝３．１Åの（１１１）面が約７０°で交差することから、実施例１で確認された（１１０）面からなる平板状の円形小粒子と同様のものであることが確認された。 When these crystals were analyzed from the lattice plane of the lattice image photograph and the angle thereof, the (111) plane with a plane interval of d = 3.1 mm intersected at about 70 °, and thus this was confirmed in Example 1. It was confirmed to be the same as the flat circular small particles having a (110) plane.
本比較例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、ほぼ全ての粒子が（１１０）面からなる平板状の円形小粒子であり、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子は存在しないことが確認された。 As a result of confirming the crystal planes of arbitrary 500 fine particles in the powder obtained in this comparative example, almost all the particles are flat circular small particles composed of (110) planes, (001) plane and the same It was confirmed that ceria microcrystal particles, which are pseudo-cubic particles composed of equivalent surfaces, do not exist.
（比較例２）
内容積５ｃｍ３の密閉型反応容器に、０．１モル／ｌの硝酸セリウム水溶液２．５ｍｌとデシルアミン０．０１ｍｌを仕込み、３５０℃に設定した加熱炉に反応容器を入れて加熱した。昇温には１．５分を要し、２０分間反応させた後、室温まで冷却し、得られた粉体をメンブランフィルターで分離して水、エタノールで洗浄した。
(Comparative Example 2)
A sealed reaction vessel having an internal volume of 5 cm 3 was charged with 2.5 ml of a 0.1 mol / l cerium nitrate aqueous solution and 0.01 ml of decylamine, and the reaction vessel was placed in a heating furnace set at 350 ° C. and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.
生成した粉体を構成する微粒子の形態を実施例１と同様にＨＲ−ＴＥＭ観察及びＥＤＸ分析したところ、図９に示すように、粒径が約３０〜１５０ｎｍの粒子が存在しており、いずれもセリアの結晶であることが確認された。 When the form of the fine particles constituting the generated powder was observed by HR-TEM and EDX analysis in the same manner as in Example 1, as shown in FIG. 9, there were particles having a particle size of about 30 to 150 nm. Were also confirmed to be ceria crystals.
これらの結晶について格子像写真の格子面とその角度から解析を行ったところ、図１０に示すような（００１）面、図１１に示すような（１１０）面、更には（２１１）面からなる粒子が存在することが確認された。 When these crystals were analyzed from the lattice plane of the lattice image photograph and their angles, they were composed of (001) plane as shown in FIG. 10, (110) plane as shown in FIG. 11, and (211) plane. The presence of particles was confirmed.
本比較例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約１０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this comparative example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 10% by mass.
（比較例３）
内容積５ｃｍ３の密閉型反応容器に、０．１モル／ｌの硝酸セリウム水溶液２．５ｍｌを仕込み、３５０℃に設定した加熱炉に反応容器を入れて加熱した。昇温には１．５分を要し、２０分間反応させた後、室温まで冷却し、得られた粉体をメンブランフィルターで分離して水、エタノールで洗浄した。
(Comparative Example 3)
A sealed reaction vessel having an internal volume of 5 cm 3 was charged with 2.5 ml of a 0.1 mol / l cerium nitrate aqueous solution, and the reaction vessel was placed in a heating furnace set at 350 ° C. and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.
生成した粉体を構成する微粒子の形態を実施例１と同様にＨＲ−ＴＥＭ観察及びＥＤＸ分析したところ、平均粒径が１μｍ以上に成長した大きな粒子が存在しており、いずれもセリアの結晶であることが確認された。 The form of the fine particles constituting the produced powder was observed by HR-TEM and EDX analysis in the same manner as in Example 1. As a result, there were large particles with an average particle diameter of 1 μm or more, both of which were ceria crystals. It was confirmed that there was.
これらの結晶について格子像写真の格子面とその角度から解析を行ったところ、図１２〜図１３に示すような（０１３）面、図１４〜図１５に示すような（０１１）面、図１６〜図１７に示すような（２１１）面、図１８〜図２０に示すような（１２３）面及び（２１１）面からなる粒子が存在することが確認された。 When these crystals were analyzed from the lattice plane of the lattice image photograph and its angle, the (013) plane as shown in FIGS. 12 to 13, the (011) plane as shown in FIGS. 14 to 15, and FIG. It was confirmed that particles having (211) plane as shown in FIG. 17 and (123) plane and (211) plane as shown in FIGS.
本比較例で得られた粉体における任意の１００個の微粒子の結晶面を確認したところ、有機物質が共存しない状態で合成した粒子においては結晶面に対する選択性はなく、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約１０質量％であることが確認された。 As a result of confirming the crystal plane of any 100 fine particles in the powder obtained in this comparative example, the particles synthesized in the absence of the organic substance have no selectivity to the crystal plane, and the (001) plane and It was confirmed that the ratio of ceria microcrystalline particles, which are pseudo-cubic particles having an equivalent surface, was about 10% by mass.
＜触媒活性試験＞
実施例２で得られた粉体を、コージエライトハニカムテストピース（３０ｍｍφ×３０ｍｍ）に２ｇ塗布し、更に０．００２ｇのＰｔを担持せしめた後、得られた触媒を用いて流通式の反応器でゆっくり昇温しながらモデル排ガスを流通させた。
<Catalytic activity test>
2 g of the powder obtained in Example 2 was applied to a cordierite honeycomb test piece (30 mmφ × 30 mm), and 0.002 g of Pt was further supported thereon. Then, a flow-type reaction was performed using the obtained catalyst. The model exhaust gas was circulated while slowly raising the temperature in the vessel.
また、比較のため、市販のＣｅＯ２粉末（比表面積１００ｍ２／ｇ）を同様にＰｔと共にコージエライトハニカムテストピースに塗布して得た触媒を用いて同様の試験を行った。 For comparison, a similar test was performed using a catalyst obtained by applying commercially available CeO 2 powder (specific surface area 100 m 2 / g) to a cordierite honeycomb test piece together with Pt.
両者の試験の結果得られた５０％浄化温度を以下に示す。 The 50% purification temperature obtained as a result of both tests is shown below.
（実施例２で得られた粉体） （市販のＣｅＯ２粉末）
ＣＯ ８０℃ １５０℃
Ｃ３Ｈ６ １２０℃ ２１０℃
ＮＯ １３５℃ ２２０℃。
(Powder obtained in Example 2) (Commercially available CeO 2 powder)
CO 80 ℃ 150 ℃
C 3 H 6 120 ° C. 210 ° C.
NO 135 ° C 220 ° C.
以上の結果から、実施例２で得られた粉体を用いて得た触媒においては、室温付近の低温から高い酸化活性が発現し、８００℃付近の高温までその触媒活性が低下しない触媒特性が得られることが確認された。したがって、本発明の触媒を排ガス浄化用触媒として用いれば、エンジンのスタートアップの際に放出される炭化水素やCOを放出することなく高効率で浄化でき、飛躍的な排ガスのクリーン化が容易に達成することが可能となる。 From the above results, the catalyst obtained by using the powder obtained in Example 2 has high catalytic activity at a low temperature around room temperature, and the catalytic properties do not decrease until a high temperature around 800 ° C. It was confirmed that it was obtained. Therefore, if the catalyst of the present invention is used as an exhaust gas purification catalyst, it can be purified with high efficiency without releasing hydrocarbons and CO released at engine start-up, and a dramatic reduction of exhaust gas can be easily achieved. It becomes possible to do.
（実施例３）
内容積５ｃｍ３の密閉型反応容器（管型オートクレーブ）に、０．２モル／ｌの水酸化セリウム懸濁液２．５ｍｌとヘキサン酸０．２ｍｌを仕込み、４００℃に設定した加熱炉に反応容器を入れて加熱した。昇温には１．５分を要し、２０分間反応させた後、室温まで冷却し、得られた粉体をメンブランフィルターで分離して水、エタノールで洗浄した。
(Example 3)
A sealed reaction vessel (tubular autoclave) with an internal volume of 5 cm 3 was charged with 2.5 ml of 0.2 mol / l cerium hydroxide suspension and 0.2 ml of hexanoic acid, and reacted in a heating furnace set at 400 ° C. The container was placed and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図２１〜図２２に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 When TEM observation and EDX analysis were performed on the form of the fine particles constituting the generated powder, as shown in FIGS. 21 to 22, there were particles such as pseudo cubic particles having an average particle diameter of about 10 nm. It was confirmed that it is a ceria crystal, and at least pseudo-cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、図２３に示すように、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約７０質量％であることが確認された。なお、図２３には、同図に示す３９個の微粒子の結晶面の測定結果を示した。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, as shown in FIG. 23, ceria, which is a pseudo-cubic particle comprising a (001) plane and an equivalent plane, as shown in FIG. It was confirmed that the ratio of microcrystalline particles was about 70% by mass. FIG. 23 shows the measurement results of the crystal planes of 39 fine particles shown in FIG.
（実施例４）
ヘキサン酸の仕込み量を０．１ｍｌとした以外は実施例３と同様にして粉体を得た。
Example 4
A powder was obtained in the same manner as in Example 3 except that the amount of hexanoic acid charged was 0.1 ml.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図２４に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 When TEM observation and EDX analysis were performed on the form of the fine particles constituting the generated powder, as shown in FIG. 24, particles such as pseudo cubic particles having an average particle diameter of about 10 nm were present, both of which were ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約６０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 60% by mass.
（実施例５）
ヘキサン酸の仕込み量を０．３ｍｌとした以外は実施例３と同様にして粉体を得た。
(Example 5)
A powder was obtained in the same manner as in Example 3 except that the amount of hexanoic acid charged was 0.3 ml.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図２５に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 When TEM observation and EDX analysis were performed on the form of fine particles constituting the generated powder, as shown in FIG. 25, particles such as pseudo cubic particles having an average particle diameter of about 10 nm were present, both of which were ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約５０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 50% by mass.
（実施例６）
内容積５ｃｍ３の密閉型反応容器（管型オートクレーブ）に、０．２モル／ｌのランタン含有水酸化セリウム懸濁液（Ｌａ含有率：ＣｅとＬａとの合計量を基準として１０モル％）２．５ｍｌとヘキサン酸０．１ｍｌを仕込み、４００℃に設定した加熱炉に反応容器を入れて加熱した。昇温には１．５分を要し、２０分間反応させた後、室温まで冷却し、得られた粉体をメンブランフィルターで分離して水、エタノールで洗浄した。
(Example 6)
In a sealed reaction vessel (tubular autoclave) with an internal volume of 5 cm 3 , a lanthanum-containing cerium hydroxide suspension of 0.2 mol / l (La content: 10 mol% based on the total amount of Ce and La) 2.5 ml and 0.1 ml of hexanoic acid were charged, and the reaction vessel was placed in a heating furnace set at 400 ° C. and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図２６に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 TEM observation and EDX analysis of the form of the fine particles constituting the generated powder revealed that there were particles such as pseudo cubic particles having an average particle diameter of about 10 nm as shown in FIG. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約５０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 50% by mass.
（実施例７）
ヘキサン酸の仕込み量を０．２ｍｌとした以外は実施例６と同様にして粉体を得た。
(Example 7)
A powder was obtained in the same manner as in Example 6 except that the amount of hexanoic acid charged was 0.2 ml.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図２７に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 As a result of TEM observation and EDX analysis of the form of fine particles constituting the generated powder, as shown in FIG. 27, particles such as pseudo cubic particles having an average particle diameter of about 10 nm are present, both of which are ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約７０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed that the content was 70% by mass.
（実施例８）
ヘキサン酸の仕込み量を０．３ｍｌとした以外は実施例６と同様にして粉体を得た。
(Example 8)
A powder was obtained in the same manner as in Example 6 except that the amount of hexanoic acid charged was 0.3 ml.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図２８に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 When TEM observation and EDX analysis were performed on the form of fine particles constituting the generated powder, as shown in FIG. 28, particles such as pseudo cubic particles having an average particle diameter of about 10 nm were present, both of which were ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約７０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed that the content was 70% by mass.
（実施例９）
ヘキサン酸の仕込み量を０．４ｍｌとした以外は実施例６と同様にして粉体を得た。
Example 9
A powder was obtained in the same manner as in Example 6 except that the amount of hexanoic acid charged was 0.4 ml.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図２９に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 As a result of TEM observation and EDX analysis of the form of fine particles constituting the generated powder, as shown in FIG. 29, particles such as pseudo cubic particles having an average particle diameter of about 10 nm are present, both of which are ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約８０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed that it was 80 mass%.
（実施例１０）
ヘキサン酸の仕込み量を０．６ｍｌとした以外は実施例６と同様にして粉体を得た。
(Example 10)
A powder was obtained in the same manner as in Example 6 except that the amount of hexanoic acid charged was 0.6 ml.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図３０に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 As a result of TEM observation and EDX analysis of the form of fine particles constituting the generated powder, as shown in FIG. 30, there are particles such as pseudo cubic particles having an average particle diameter of about 10 nm, both of which are ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約９０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 90% by mass.
（実施例１１）
ランタン含有水酸化セリウム懸濁液の仕込み量を１．９ｍｌとした以外は実施例１０と同様にして粉体を得た。
(Example 11)
A powder was obtained in the same manner as in Example 10 except that the charged amount of the lanthanum-containing cerium hydroxide suspension was changed to 1.9 ml.
生成した粉体を構成する微粒子の形態をＴＥＭ観察及びＥＤＸ分析したところ、図３１に示すように、平均粒径が約１０ｎｍの擬似立方体粒子等の粒子が存在しており、いずれもセリアの結晶であり、少なくとも擬似立方体粒子は単結晶からなる単分散ナノ結晶であることが確認された。 As a result of TEM observation and EDX analysis of the form of fine particles constituting the generated powder, as shown in FIG. 31, there are particles such as pseudo cubic particles having an average particle diameter of about 10 nm, both of which are ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.
本実施例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、（００１）面およびそれと等価な面からなる擬似立方体状の粒子であるセリア微結晶粒子の比率が約５０質量％であることが確認された。 When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 50% by mass.
（比較例４）
０．２モル／ｌの硝酸セリウム水溶液５０ｍｌを１モル／ｌのアンモニア水を用いて中和せしめて３０分間撹拌した後、得られた沈殿を分離し、１５０℃で５時間乾燥し、さらに４００℃で５時間焼成してセリアの粉体を得た。
(Comparative Example 4)
After neutralizing 50 ml of 0.2 mol / l cerium nitrate aqueous solution with 1 mol / l ammonia water and stirring for 30 minutes, the resulting precipitate was separated, dried at 150 ° C. for 5 hours, and further 400 Ceria powder was obtained by baking at 5 ° C. for 5 hours.
本比較例で得られた粉体における任意の５００個の微粒子の結晶面を確認したところ、沈殿法で合成した粒子においては結晶面に対する選択性はなく、明確な結晶面の出た粒子は見られなかった。 When the crystal face of any 500 fine particles in the powder obtained in this comparative example was confirmed, the particles synthesized by the precipitation method had no selectivity for the crystal face, and particles with a clear crystal face were not seen. I couldn't.
＜酸素貯蔵量試験＞
実施例３及び比較例４で得られたセリア微結晶粒子からなる粉体の酸素貯蔵量（ＯＳＣ）を以下の方法で測定し、比較した。
<Oxygen storage amount test>
The oxygen storage amount (OSC) of the powder composed of ceria microcrystal particles obtained in Example 3 and Comparative Example 4 was measured and compared by the following method.
すなわち、各試料を１５ｍｇ熱重量分析計のサンプルセルに設置し、１５０℃、２００℃、４００℃の各試験温度において水素による還元と酸素による酸化を繰り返し行って可逆的な重量変化を測定した。ブランクとしてＯＳＣを持たないジルコニア粉末を用い、各試料の測定値からジルコニアで得られた値を差し引いて各試料のＯＳＣを求めた。得られた結果を図３２に示す。 That is, each sample was placed in a sample cell of a 15 mg thermogravimetric analyzer, and reversible weight change was measured by repeatedly performing reduction with hydrogen and oxidation with oxygen at each test temperature of 150 ° C., 200 ° C., and 400 ° C. A zirconia powder having no OSC was used as a blank, and the OSC of each sample was determined by subtracting the value obtained with zirconia from the measured value of each sample. The obtained result is shown in FIG.
図３２に示した結果から明らかなように、１５０℃、２００℃、４００℃の各試験温度において、比較例４で得られたセリア微結晶粒子からなる粉体に比べて、実施例３で得られたセリア微結晶粒子からなる粉体の方が圧倒的に大きなＯＳＣを有していることが確認された。 As is apparent from the results shown in FIG. 32, it was obtained in Example 3 as compared with the powder composed of ceria microcrystalline particles obtained in Comparative Example 4 at each test temperature of 150 ° C., 200 ° C., and 400 ° C. It was confirmed that the powder composed of the ceria microcrystal particles thus obtained has an overwhelmingly large OSC.
＜耐熱性試験＞
実施例３及び実施例９で得られたセリア微結晶粒子からなる粉体をそれぞれ大気中４００℃で５時間加熱し、その後の微粒子の形態をＴＥＭにより観察した。得られた結果を図３３（実施例３）及び図３４（実施例９）に示す。
<Heat resistance test>
The powders composed of ceria microcrystalline particles obtained in Example 3 and Example 9 were each heated in the atmosphere at 400 ° C. for 5 hours, and the morphology of the subsequent fine particles was observed by TEM. The obtained results are shown in FIG. 33 (Example 3) and FIG. 34 (Example 9).
図３３及び図３４に示した結果から明らかなように、実施例３で得られたセリア微結晶粒子からなる粉体も耐熱性に優れているが、実施例９で得られた第二成分としてランタンを含有するセリア微結晶粒子からなる粉体の方がより耐熱性に優れていることが確認された。 As is clear from the results shown in FIG. 33 and FIG. 34, the powder composed of ceria microcrystalline particles obtained in Example 3 is also excellent in heat resistance, but as the second component obtained in Example 9, It was confirmed that the powder composed of ceria microcrystalline particles containing lanthanum is more excellent in heat resistance.
以上説明したように、本発明の酸化物微結晶粒子からなる粉体の製造方法によれば、活性な結晶面からなる酸化物微結晶粒子の比率を従来より大幅に向上させることが可能となる。そのため、本発明によれば、従来は得ることができなかった活性な結晶面からなる酸化物微結晶粒子が５０質量％以上を占める酸化物微結晶粒子の粉体を提供することが可能となり、本発明の酸化物微結晶粒子からなる粉体を用いて得た本発明の触媒は低温及び高温触媒活性に優れたものとなる。したがって、本発明は、排ガス浄化用触媒、酸化触媒等の各種触媒を得るための技術等として非常に有用である。 As described above, according to the method for producing a powder composed of oxide microcrystal particles of the present invention, the ratio of the oxide microcrystal particles composed of active crystal faces can be significantly improved as compared with the conventional method. . Therefore, according to the present invention, it is possible to provide a powder of oxide microcrystal particles in which the oxide crystallite particles composed of active crystal faces that could not be obtained conventionally account for 50% by mass or more, The catalyst of the present invention obtained by using the powder comprising the oxide microcrystal particles of the present invention is excellent in low temperature and high temperature catalytic activity. Therefore, the present invention is very useful as a technique for obtaining various catalysts such as an exhaust gas purification catalyst and an oxidation catalyst.
Claims (11)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2006268317A JP5116276B2 (en) | 2006-01-23 | 2006-09-29 | Powder comprising oxide microcrystal particles, catalyst using the same, and method for producing the same |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2006013461 | 2006-01-23 | ||
| JP2006013461 | 2006-01-23 | ||
| JP2006268317A JP5116276B2 (en) | 2006-01-23 | 2006-09-29 | Powder comprising oxide microcrystal particles, catalyst using the same, and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2007217265A JP2007217265A (en) | 2007-08-30 |
| JP5116276B2 true JP5116276B2 (en) | 2013-01-09 |
Family
ID=38494947
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2006268317A Expired - Fee Related JP5116276B2 (en) | 2006-01-23 | 2006-09-29 | Powder comprising oxide microcrystal particles, catalyst using the same, and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP5116276B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4961611B2 (en) * | 2007-12-26 | 2012-06-27 | 株式会社豊田中央研究所 | Powder for purifying automobile exhaust, catalyst for purifying automobile exhaust using the same, and method for producing the same |
| CN102186581B (en) * | 2008-10-17 | 2013-11-20 | 优美科触媒日本有限公司 | Exhaust gas purifying catalyst and method for purifying exhaust gas using the catalyst |
| JP2010216839A (en) * | 2009-03-13 | 2010-09-30 | Toyota Central R&D Labs Inc | Method of detecting existence of chemiluminescence deriving from solid surface reaction, method of identifying chemical substance species deriving from solid surface reaction, and device used in these methods for detecting chemiluminescence deriving from solid surface reaction |
| JP5641349B2 (en) * | 2011-03-28 | 2014-12-17 | トヨタ自動車株式会社 | Powder material rich in cuboid-shaped ceria nanoparticles and method for producing the same |
| JP5703924B2 (en) * | 2011-04-15 | 2015-04-22 | トヨタ自動車株式会社 | Columnar ceria catalyst |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100477939B1 (en) * | 2002-04-15 | 2005-03-18 | 주식회사 엘지화학 | Mehtod for preparing single craystalline cerium oxide powders |
-
2006
- 2006-09-29 JP JP2006268317A patent/JP5116276B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2007217265A (en) | 2007-08-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3262044B2 (en) | Composite oxide carrier and composite oxide-containing catalyst | |
| KR102580600B1 (en) | Cerium- and zirconium-based mixed oxides | |
| KR101286799B1 (en) | Composition including a lanthanum perovskite on an alumina or aluminium oxyhydroxide substrate, preparation method and use in catalysis | |
| RU2509725C2 (en) | Composition based on cerium oxide and zirconium oxide having specific porosity, method of production and use in catalysis | |
| CN112657487B (en) | High porosity cerium and zirconium containing oxides | |
| EP2505262B1 (en) | Complex oxide, method for producing same and exhaust gas purifying catalyst | |
| EP2959962B1 (en) | Ceria-zirconia complex oxide material and method for producing same | |
| US10010876B2 (en) | Catalyst for high temperature steam reforming | |
| JP5116276B2 (en) | Powder comprising oxide microcrystal particles, catalyst using the same, and method for producing the same | |
| JP3265534B2 (en) | Exhaust gas purification catalyst | |
| Megarajan et al. | Improved catalytic activity of PrMO 3 (M= Co and Fe) perovskites: synthesis of thermally stable nanoparticles by a novel hydrothermal method | |
| JP5660006B2 (en) | Method for producing Co3O4 / CeO2 composite catalyst for exhaust gas purification and catalyst obtained thereby | |
| JPWO2021192871A5 (en) | ||
| JP5915520B2 (en) | Exhaust gas purification catalyst | |
| JP4165419B2 (en) | Method for producing metal oxide particles and exhaust gas purification catalyst | |
| JP4972868B2 (en) | Surface-modified ceria / zirconia hydrated oxide, oxide thereof, production method thereof, and use thereof | |
| JP4961611B2 (en) | Powder for purifying automobile exhaust, catalyst for purifying automobile exhaust using the same, and method for producing the same | |
| EP1126914A1 (en) | Preparation of nanocrystalline and dispersible supported metal catalysts | |
| JP2007136339A (en) | Catalytic particle and its manufacturing method | |
| WO2017094688A1 (en) | Steam reforming catalyst for hydrocarbons | |
| JP5967015B2 (en) | Exhaust gas purification catalyst | |
| JP2005170775A (en) | Oxide powder, method for producing the same. and exhaust gas cleaning catalyst | |
| Zahir et al. | Perovskites with cotton-like morphology consisting of nanoparticles and nanorods: Their synthesis by the combustion method and their NOx adsorption behavior | |
| JP2014237078A (en) | Exhaust gas purifying catalyst and method for producing the same | |
| JP2003275588A (en) | Co shift reaction catalyst |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20090716 |
|
| RD02 | Notification of acceptance of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7422 Effective date: 20090716 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20110824 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20120628 |
|
| A601 | Written request for extension of time |
Free format text: JAPANESE INTERMEDIATE CODE: A601 Effective date: 20120824 |
|
| A602 | Written permission of extension of time |
Free format text: JAPANESE INTERMEDIATE CODE: A602 Effective date: 20120829 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20120926 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20121016 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20121016 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20151026 Year of fee payment: 3 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| LAPS | Cancellation because of no payment of annual fees |