JP2003073123A - Composite oxide, method for producing the same, and promoter for purifying exhaust gas - Google Patents
Composite oxide, method for producing the same, and promoter for purifying exhaust gasInfo
- Publication number
- JP2003073123A JP2003073123A JP2001261260A JP2001261260A JP2003073123A JP 2003073123 A JP2003073123 A JP 2003073123A JP 2001261260 A JP2001261260 A JP 2001261260A JP 2001261260 A JP2001261260 A JP 2001261260A JP 2003073123 A JP2003073123 A JP 2003073123A
- Authority
- JP
- Japan
- Prior art keywords
- composite oxide
- ceo
- zro
- oxide
- exhaust gas
- 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.)
- Granted
Links
- 239000002131 composite material Substances 0.000 title claims abstract description 71
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 230000009467 reduction Effects 0.000 claims abstract description 16
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 13
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 13
- 229910052684 Cerium Inorganic materials 0.000 claims abstract description 10
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 9
- 238000000034 method Methods 0.000 claims description 25
- 239000002244 precipitate Substances 0.000 claims description 19
- 229910052751 metal Inorganic materials 0.000 claims description 12
- 239000006104 solid solution Substances 0.000 claims description 12
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 10
- 230000032683 aging Effects 0.000 claims description 9
- 239000000243 solution Substances 0.000 claims description 8
- 239000003426 co-catalyst Substances 0.000 claims description 7
- 238000000975 co-precipitation Methods 0.000 claims description 7
- 229910000510 noble metal Inorganic materials 0.000 claims description 7
- 150000001785 cerium compounds Chemical class 0.000 claims description 5
- 238000010335 hydrothermal treatment Methods 0.000 claims description 5
- 150000003755 zirconium compounds Chemical class 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- 239000002612 dispersion medium Substances 0.000 claims description 3
- 230000003647 oxidation Effects 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 claims description 2
- 239000000725 suspension Substances 0.000 claims description 2
- 239000003795 chemical substances by application Substances 0.000 claims 1
- 239000007789 gas Substances 0.000 abstract description 21
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 7
- 229910052760 oxygen Inorganic materials 0.000 abstract description 7
- 239000001301 oxygen Substances 0.000 abstract description 7
- 238000003860 storage Methods 0.000 abstract description 4
- 230000004888 barrier function Effects 0.000 abstract description 2
- 230000015572 biosynthetic process Effects 0.000 abstract 1
- 239000000843 powder Substances 0.000 description 24
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
- 230000007423 decrease Effects 0.000 description 15
- 239000003054 catalyst Substances 0.000 description 13
- 238000002441 X-ray diffraction Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 239000002243 precursor Substances 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- 229910052761 rare earth metal Inorganic materials 0.000 description 7
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 150000004703 alkoxides Chemical class 0.000 description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- 239000010948 rhodium Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 3
- 125000004429 atom Chemical group 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003472 neutralizing effect Effects 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- GEIAQOFPUVMAGM-UHFFFAOYSA-N ZrO Inorganic materials [Zr]=O GEIAQOFPUVMAGM-UHFFFAOYSA-N 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- -1 cerium ions Chemical class 0.000 description 1
- XQTIWNLDFPPCIU-UHFFFAOYSA-N cerium(3+) Chemical class [Ce+3] XQTIWNLDFPPCIU-UHFFFAOYSA-N 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000001226 reprecipitation Methods 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000002411 thermogravimetry Methods 0.000 description 1
- GBNDTYKAOXLLID-UHFFFAOYSA-N zirconium(4+) ion Chemical compound [Zr+4] GBNDTYKAOXLLID-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Catalysts (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
(57)【要約】
【課題】高い比表面積と高い酸素吸蔵放出能とが両立し
た排ガス浄化用助触媒とする。
【解決手段】CeO2と、ZrO2と、CeO2及びZrO2と反応しな
い金属酸化物との複合酸化物からなり、Ce及びZrが規則
配列したパイロクロア相をもつ複合酸化物を担体とす
る。CeO2−ZrO2複合酸化物と、CeO2及びZrO2と反応しな
い金属酸化物とが互いの障壁となるために、パイロクロ
ア相生成のための還元処理時の高熱による粒成長が抑制
され、パイロクロア相生成により酸素吸蔵放出能が向上
する。(57) [Problem] To provide an exhaust gas purifying cocatalyst having both high specific surface area and high oxygen storage / release capability. The carrier comprises a composite oxide of CeO 2 , ZrO 2, and a metal oxide that does not react with CeO 2 and ZrO 2 and has a pyrochlore phase in which Ce and Zr are regularly arranged. Since the CeO 2 -ZrO 2 composite oxide and the metal oxide that does not react with CeO 2 and ZrO 2 serve as a barrier to each other, grain growth due to high heat during the reduction treatment for generating the pyrochlore phase is suppressed, and the pyrochlore Oxygen storage / release capacity is improved by the phase formation.
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、充分な比表面積を
有するとともに高い酸素吸蔵放出能（以下 OSCという）
を有する排ガス浄化用助触媒と、その排ガス浄化用助触
媒の担体として用いられる複合酸化物及びその製造方法
に関する。TECHNICAL FIELD The present invention has a sufficient specific surface area and a high oxygen storage / release capacity (hereinafter referred to as OSC).
And a composite oxide used as a carrier for the exhaust gas-purifying promoter, and a method for producing the same.
【０００２】[0002]
【従来の技術】従来より自動車の排ガス浄化用触媒とし
て、排ガス中のCO及びHCの酸化とNOxの還元とを同時に
行って浄化する三元触媒が用いられている。このような
三元触媒としては、例えばコーディエライトなどからな
る耐熱性ハニカム基材にγ-Al2O3からなる担体層を形成
し、その担体層に白金（Pt）やロジウム（Rh)などの触
媒金属を担持させたものが広く知られている。2. Description of the Related Art Conventionally, as a catalyst for purifying exhaust gas of automobiles, a three-way catalyst has been used which purifies the exhaust gas by simultaneously oxidizing CO and HC and reducing NO x . As such a three-way catalyst, for example, a carrier layer made of γ-Al 2 O 3 is formed on a heat-resistant honeycomb substrate made of cordierite or the like, and platinum (Pt) or rhodium (Rh) is formed on the carrier layer. It is widely known that the above catalyst metal is supported.
【０００３】ところで排ガス浄化用触媒に用いられる担
体の条件としては、比表面積が大きく耐熱性が高いこと
が挙げられ、一般には Al2O3、SiO2、ZrO2、TiO2などが
用いられることが多い。また OSCをもつCeO2を助触媒と
して併用することで、排ガスの雰囲気変動を緩和するこ
とも行われている。The condition of the carrier used for the exhaust gas purifying catalyst is that it has a large specific surface area and high heat resistance. Generally, Al 2 O 3 , SiO 2 , ZrO 2 , TiO 2 and the like are used. There are many. Also, by using CeO 2 with OSC as a co-catalyst together, it is possible to mitigate the atmospheric fluctuation of exhaust gas.
【０００４】ところが従来の排ガス浄化用触媒では、 8
00℃を超えるような高温にさらされると、シンタリング
による担体の比表面積の低下、触媒金属の粒成長が生
じ、さらにはCeO2のもつ OSCも低下するために、浄化性
能が著しく低下するという不具合があった。However, in the conventional exhaust gas purifying catalyst,
When exposed to a high temperature of more than 00 ° C, the specific surface area of the carrier decreases due to sintering, the grain growth of the catalytic metal occurs, and the OSC of CeO 2 also decreases, resulting in a marked decrease in purification performance. There was a problem.
【０００５】また近年の排ガス規制の強化により、エン
ジン始動からごく短い時間にも排ガスを浄化する必要性
がきわめて高くなっている。そのためには、より低温で
触媒を活性化し、排出規制成分を浄化しなければならな
い。中でもPtをCeO2に担持した助触媒は、低温からCOを
浄化する性能に長けている。このような助触媒を用いれ
ば、COが低温で着火されることによってPtのCO吸着被毒
が緩和され、HCの着火性が向上する。また、これによっ
て触媒表面の暖機が促進されるため、低温域からHCを浄
化することができる。さらに、この助触媒では、水性ガ
スシフト反応によって低温域でH2が生成されるため、そ
のH2とNOx との反応により低温域からNO x を還元浄化す
ることができる。In addition, due to the recent tightening of exhaust gas regulations,
Need to purify exhaust gas in a very short time after starting gin
Is extremely high. For that, at lower temperatures
It is necessary to activate the catalyst and purify emission control components.
Yes. Above all, Pt is CeO2The co-catalyst supported on carbon dioxide can emit CO from a low temperature.
Good at purifying performance. Use such a promoter
For example, when CO is ignited at a low temperature, CO adsorption poisoning of Pt
Is alleviated, and the ignitability of HC is improved. Also, with this
As the catalyst surface is warmed up, the HC is cleaned from the low temperature range.
Can be converted. In addition, the co-catalyst has
H at low temperature due to shift reaction2Is generated,
H2And NOx NO from low temperature due to reaction with x Reduce and purify
You can
【０００６】しかし従来のCeO2にPtなどを担持した助触
媒においては、実際の排ガス中における耐久性に乏し
く、熱によってCeO2がシンタリングしてしまい実用的で
はない。実際の排ガス中で使用するためには、CeO2の性
質を失うことなく耐熱性を向上させる必要性がある。ま
たCeO2のシンタリングに伴ってPtに粒成長が生じ活性が
低下するため、担体上のPtの安定化が求められている。[0006] However, in the co-catalyst carrying and Pt to the conventional CeO 2, poor durability in actual in the exhaust gas, CeO 2 is not practical would be sintered by heat. For use in actual exhaust gas, it is necessary to improve the heat resistance without losing the properties of CeO 2 . In addition, Pt on the carrier is required to be stabilized because grain growth occurs in Pt due to sintering of CeO 2 and the activity decreases.
【０００７】また担体にCeO2を含む三元触媒でも、高温
にさらされるとCeO2によって発現される OSCが低下す
る。これはCeO2のシンタリング及び担持されている貴金
属の粒成長と、貴金属の酸化、RhのCeO2への固溶などが
原因である。そして OSCが低い（CeO2量が少ない）触媒
においては、変動する雰囲気に貴金属がさらされやす
く、貴金属の劣化（凝集や固溶）がさらに促進されてし
まう。Even with a three-way catalyst containing CeO 2 as a carrier, the OSC expressed by CeO 2 decreases when exposed to high temperatures. This is due to sintering of CeO 2 and grain growth of the precious metal supported, oxidation of the precious metal, and solid solution of Rh in CeO 2 . And in a catalyst with a low OSC (a small amount of CeO 2 ), the noble metal is easily exposed to the changing atmosphere, and the deterioration (aggregation or solid solution) of the noble metal is further promoted.
【０００８】そこで特開平8-215569号公報には、金属ア
ルコキシドから調製されたCeO2−ZrO2複合酸化物を用い
る技術が開示されている。金属アルコキシドからゾルゲ
ル法により調製されたCeO2−ZrO2複合酸化物は、CeとZr
とが原子又は分子レベルで複合化されて固溶体となって
いるため、耐熱性が向上し初期から耐久後まで高い OSC
が確保される。Japanese Unexamined Patent Publication (Kokai) No. 8-215569 discloses a technique using a CeO 2 --ZrO 2 composite oxide prepared from a metal alkoxide. CeO 2 -ZrO 2 composite oxide prepared by sol-gel method from metal alkoxide is Ce and Zr
Since and are compounded at the atomic or molecular level to form a solid solution, the heat resistance improves and the OSC is high from the beginning to the end of durability.
Is secured.
【０００９】このような複合酸化物は、アルコキシド
法、共沈法などにより複数の金属元素を含む酸化物前駆
体を調製し、それを焼成することで製造することができ
る。中でも共沈法は、アルコキシド法などに比べて原料
コストが安価であるため、得られる複合酸化物も安価と
なる利点があり、複合酸化物の製造に広く用いられてい
る。Such a complex oxide can be produced by preparing an oxide precursor containing a plurality of metal elements by an alkoxide method, a coprecipitation method or the like, and firing it. Among them, the coprecipitation method has a merit that the raw material cost is lower than that of the alkoxide method and the like, and thus the obtained composite oxide is also inexpensive, and is widely used in the production of the composite oxide.
【００１０】ところが上記した特開平8-215569号公報に
記載の複合酸化物では、 OSCがまだ不充分であり、さら
なる OSCの向上が求められている。そこで特開平11−16
5067号公報には、セリウム（III）塩とジルコニウム（I
V）塩を含む溶液から共沈法によって沈殿を形成し、そ
の沈殿を不活性雰囲気又は非酸化性雰囲気下で 800〜10
00℃に加熱保持する方法が記載されている。この方法に
よれば、得られる複合酸化物はパイロクロア相に帰属す
るＸ線回折ピークを有し、高い OSCを示す。However, the composite oxide described in Japanese Patent Application Laid-Open No. 8-215569 mentioned above is still insufficient in OSC, and further improvement in OSC is required. Therefore, JP 11-16
No. 5067 discloses cerium (III) salt and zirconium (I
V) A precipitate is formed from a salt-containing solution by a coprecipitation method, and the precipitate is formed under an inert atmosphere or a non-oxidizing atmosphere at a ratio of 801 to 10
A method of heating and holding at 00 ° C is described. According to this method, the obtained composite oxide has an X-ray diffraction peak attributed to the pyrochlore phase and exhibits a high OSC.
【００１１】[0011]
【発明が解決しようとする課題】特開平11−165067号公
報に記載の方法によれば、確かに高い OSCを有するCeO2
−ZrO2複合酸化物が得られる。しかしながらこの方法で
は、 800〜1000℃に加熱保持しているためにCeO2−ZrO2
複合酸化物の比表面積の低下が避けられず、排ガス浄化
用助触媒として用いた場合には実用的な高い浄化活性を
得ることは困難である。According to the method described in Japanese Patent Laid-Open No. 11-165067, it is possible to obtain CeO 2 having a high OSC.
A -ZrO 2 composite oxide is obtained. However, in this method, since it is heated and held at 800 to 1000 ° C, CeO 2 -ZrO 2
It is unavoidable that the specific surface area of the composite oxide decreases, and it is difficult to obtain a practical high purification activity when used as an exhaust gas purification promoter.
【００１２】本発明はこのような事情に鑑みてなされた
ものであり、高い比表面積と高い OSCとが両立した排ガ
ス浄化用助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 circumstances, and an object thereof is to provide an exhaust gas purifying cocatalyst having both a high specific surface area and a high OSC.
【００１３】[0013]
【課題を解決するための手段】上記課題を解決できる本
発明の複合酸化物の特徴は、CeO2と、ZrO2と、CeO2及び
ZrO2と反応しない金属酸化物との複合酸化物からなり、
Ce及びZrが規則配列したパイロクロア相をもつことにあ
る。The features of the composite oxide of the present invention which can solve the above-mentioned problems are that CeO 2 , ZrO 2 , CeO 2 and
Consisting of a composite oxide with a metal oxide that does not react with ZrO 2 ,
Ce and Zr have an ordered pyrochlore phase.
【００１４】CeO2とZrO2は少なくとも一部が互いに固溶
した固溶体を形成していることが望ましく、CeO2及びZr
O2と反応しない金属酸化物は Al2O3であることが望まし
い。[0014] CeO 2 and ZrO 2 is desirably forms at least a part of a solid solution with each other a solid solution, CeO 2 and Zr
The metal oxide that does not react with O 2 is preferably Al 2 O 3 .
【００１５】また本発明の複合酸化物を製造できる本発
明の複合酸化物の製造方法の特徴は、セリウム化合物
と、ジルコニウム化合物と、酸化物がCeO2及びZrO2と反
応しない金属の化合物の溶液に沈殿剤を添加して共沈法
により沈殿物を生成し、沈殿物を焼成した後、還元性雰
囲気中にて 800〜1200℃で加熱保持する還元処理を行う
ことにある。The characteristic feature of the method for producing a composite oxide of the present invention that can produce the composite oxide of the present invention is that a solution of a cerium compound, a zirconium compound, and a compound of a metal whose oxide does not react with CeO 2 and ZrO 2. A precipitant is added to the above to generate a precipitate by the coprecipitation method, and after the precipitate is baked, a reduction treatment is performed by heating and holding at 800 to 1200 ° C in a reducing atmosphere.
【００１６】本発明の製造方法において、沈殿物の焼成
前に、水又は水を含む溶液を分散媒とした懸濁状態また
は系内に水が充分に存在する状態で沈殿物の熟成処理を
行うことが望ましい。この熟成処理は、0.11〜 0.2MPa
の圧力及び 100〜 200℃の温度で処理する水熱処理であ
ることが特に望ましい。In the production method of the present invention, before calcination of the precipitate, aging treatment of the precipitate is carried out in a suspended state using water or a solution containing water as a dispersion medium or in a state where water is sufficiently present in the system. Is desirable. This aging process is 0.11-0.2MPa
It is particularly preferable that the hydrothermal treatment is carried out at a pressure of 100 to 200 ° C.
【００１７】そして本発明の排ガス浄化用助触媒の特徴
は、本発明の複合酸化物に貴金属を担持してなることに
ある。A feature of the exhaust gas purifying promoter of the present invention is that the complex oxide of the present invention carries a noble metal.
【００１８】[0018]
【発明の実施の形態】本発明の複合酸化物の製造方法で
は、共沈後に焼成すると、少なくともCeO2−ZrO2複合酸
化物と、CeO2及びZrO2と反応しない金属酸化物とが生成
する。そしてCeO2及びZrO2と反応しない金属酸化物がCe
O2−ZrO2複合酸化物の間に介在している。したがって、
還元性雰囲気中にて 800〜1200℃で加熱保持する後述の
還元処理の際には、CeO2−ZrO2複合酸化物とその反応し
ない金属酸化物が互いに障壁となるために粒成長が抑制
され、得られたパイロクロア相をもつ本発明の複合酸化
物は高い比表面積を有する。BEST MODE FOR CARRYING OUT THE INVENTION According to the method for producing a composite oxide of the present invention, at least a CeO 2 --ZrO 2 composite oxide and a metal oxide that does not react with CeO 2 and ZrO 2 are formed by firing after coprecipitation. . And the metal oxide that does not react with CeO 2 and ZrO 2 is Ce
It is present between O 2 —ZrO 2 composite oxides. Therefore,
During the reduction treatment described below, in which the material is heated and held at 800 to 1200 ° C in a reducing atmosphere, grain growth is suppressed because the CeO 2 -ZrO 2 composite oxide and the unreacted metal oxide act as barriers to each other. The obtained composite oxide of the present invention having a pyrochlore phase has a high specific surface area.
【００１９】そして本発明の複合酸化物は、Ce及びZrが
規則配列したパイロクロア相を有しているため、特開平
11−165067号公報に記載の複合酸化物と同様に高い OSC
が発現される。したがって本発明の複合酸化物に貴金属
を担持してなる本発明の排ガス浄化用助触媒によれば、
高い比表面積と高い OSCとを併せ持ち、実用的な高い浄
化活性が発現される。The composite oxide of the present invention has a pyrochlore phase in which Ce and Zr are regularly arranged.
High OSC similar to the composite oxide described in 11-165067
Is expressed. Therefore, according to the exhaust gas purifying promoter of the present invention in which a noble metal is supported on the composite oxide of the present invention,
It has a high specific surface area and a high OSC, and exhibits a high practical purifying activity.
【００２０】CeO2及びZrO2と反応しない金属酸化物とし
ては、 Al2O3、SiO2、TiO2などが例示される。中でも耐
熱性に優れた Al2O3が特に望ましく、その複合酸化物は
耐熱性にきわめて優れている。Examples of the metal oxide that does not react with CeO 2 and ZrO 2 include Al 2 O 3 , SiO 2 and TiO 2 . Among them, Al 2 O 3 having excellent heat resistance is particularly desirable, and the composite oxide thereof has extremely excellent heat resistance.
【００２１】本発明の複合酸化物における各金属の構成
比率は、Ce／Zr原子比が１／９〜９／１とすることが好
ましく、３／７〜７／３とするのが特に好ましい。Ceが
この範囲より少ないと OSCが不足し、Zrがこの範囲より
少ないとCeO2−ZrO2複合酸化物の安定性が低下するため
比表面積が低くなってしまう。The composition ratio of each metal in the composite oxide of the present invention is preferably Ce / Zr atomic ratio of 1/9 to 9/1, and particularly preferably 3/7 to 7/3. If Ce is less than this range, the OSC will be insufficient, and if Zr is less than this range, the stability of the CeO 2 —ZrO 2 composite oxide will decrease and the specific surface area will decrease.
【００２２】CeO2−ZrO2複合酸化物は、CeO2とZrO2とは
少なくとも一部が互いに固溶していることが望ましい。
これにより耐熱性がさらに向上し、比表面積の低下をさ
らに抑制できるとともにさらに高い OSCが発現される。In the CeO 2 -ZrO 2 composite oxide, it is desirable that CeO 2 and ZrO 2 are at least partially in solid solution with each other.
As a result, the heat resistance is further improved, the decrease in specific surface area can be further suppressed, and a higher OSC can be expressed.
【００２３】またCeO2及びZrO2と反応しない金属酸化物
の金属をＭとすれば、原子比でＭ／（Ce＋Zr）＝１／５
〜５／１の範囲が好ましく、１／３〜３／１の範囲が特
に好ましい。金属Ｍがこの範囲より少ないと比表面積が
低くなり、金属Ｍがこの範囲より多くなるとCeO2量が相
対的に減少する結果 OSCが低くなってしまう。When the metal of the metal oxide that does not react with CeO 2 and ZrO 2 is M, the atomic ratio is M / (Ce + Zr) = 1/5.
The range of ˜5 / 1 is preferable, and the range of ⅓ to 3/1 is particularly preferable. When the amount of the metal M is less than this range, the specific surface area is low, and when the amount of the metal M is more than this range, the amount of CeO 2 is relatively reduced, resulting in a lower OSC.
【００２４】本発明の複合酸化物においてCeO2及びZrO2
と反応しない金属酸化物が Al2O3である場合には、さら
に希土類元素酸化物を含み、希土類元素酸化物の70mol%
以上が Al2O3中に固溶していることが望ましい。これに
より Al2O3の耐熱性が向上するとともに、希土類元素酸
化物の固溶によるCeO2の OSCの低下を抑制することがで
きる。希土類元素酸化物の90mol%以上が Al2O3中に固溶
していることがさらに望ましい。この希土類元素酸化物
としては、La，Nd，Sm，Prなどの酸化物が例示される
が、 La2O3が最も好ましい。In the composite oxide of the present invention, CeO 2 and ZrO 2
When the metal oxide that does not react with Al 2 O 3 further contains a rare earth element oxide, 70 mol% of the rare earth element oxide
It is desirable that the above is a solid solution in Al 2 O 3 . As a result, the heat resistance of Al 2 O 3 is improved, and the decrease in OSC of CeO 2 due to the solid solution of the rare earth element oxide can be suppressed. It is more desirable that 90 mol% or more of the rare earth element oxide be in solid solution in Al 2 O 3 . Examples of the rare earth element oxide include oxides of La, Nd, Sm, Pr and the like, but La 2 O 3 is most preferable.
【００２５】なお希土類元素酸化物を含む場合には、希
土類元素原子数とAl原子数の合計を前記金属Ｍの原子数
とし、CeO2−ZrO2複合酸化物との組成比を上述の原子比
範囲とすればよい。When a rare earth element oxide is included, the total number of rare earth element atoms and Al atoms is the number of atoms of the metal M, and the composition ratio with the CeO 2 —ZrO 2 composite oxide is the above atomic ratio. It should be a range.
【００２６】そして本発明の複合酸化物は、上記の特有
の構成を有しているために後述の還元処理後あるいは高
温耐久後にも、10〜60m2／ｇと従来の（Ce，Zr）O2系助
触媒に比べ大きな比表面積を有している。Since the composite oxide of the present invention has the above-mentioned specific structure, it is 10 to 60 m 2 / g even after the reduction treatment described later or after the high temperature durability, and the conventional (Ce, Zr) 2 O 3 It has a larger specific surface area than the two- system promoter.
【００２７】本発明の複合酸化物を製造できる本発明の
複合酸化物の製造方法では、セリウム化合物と、ジルコ
ニウム化合物と、酸化物がCeO2及びZrO2と反応しない金
属の化合物の溶液に沈殿剤を添加して共沈法により沈殿
物を生成し、得られた沈殿物を焼成した後、還元性雰囲
気中にて 800〜1200℃で加熱保持する還元処理を行って
いる。In the method for producing a composite oxide of the present invention capable of producing the composite oxide of the present invention, a cerium compound, a zirconium compound and a compound of a metal compound whose oxide does not react with CeO 2 and ZrO 2 are added as a precipitant. Is added to produce a precipitate by a coprecipitation method, the obtained precipitate is baked, and then a reduction treatment is performed by heating and holding at 800 to 1200 ° C in a reducing atmosphere.
【００２８】セリウム化合物及びジルコニウム化合物と
しては、硝酸塩、硫酸塩、塩化物などの水溶性化合物を
用いることができる。また沈殿剤は、アンモニア、アル
カリ金属の水酸化物、アルカリ金属の炭酸塩などを用い
ることができる。セリウム化合物及びジルコニウム化合
物が共存する混合水溶液から共沈させた後に焼成してCe
O2及びZrO2を生成してもよいし、CeO2前駆体の沈殿とZr
O2前駆体の沈殿をそれぞれ形成しこの２種類の沈殿を混
合してから焼成することもできる。As the cerium compound and zirconium compound, water-soluble compounds such as nitrates, sulfates and chlorides can be used. As the precipitant, ammonia, hydroxide of alkali metal, carbonate of alkali metal, or the like can be used. Ce was co-precipitated from a mixed aqueous solution in which a cerium compound and a zirconium compound coexisted and then baked to obtain Ce.
O 2 and ZrO 2 may be produced, or precipitation of CeO 2 precursor and ZrO 2
It is also possible to form precipitates of O 2 precursors respectively, and to mix these two kinds of precipitates and then to bake.
【００２９】沈殿の析出方法には様々な調節方法があ
り、アンモニア水などを瞬時に添加し強撹拌する方法
や、過酸化水素などを加えることで酸化物前駆体の沈殿
し始めるpHを調節した後、アンモニア水などで沈殿を析
出させる方法などがある。またアンモニア水などで中和
させる際にかかる時間を充分に長くし、好ましくは10分
以上で中和させる方法や、pHをモニターしながら段階的
に中和する又は所定のpHに保つような緩衝溶液を添加す
る方法などがある。There are various methods for controlling the precipitation, such as a method of instantaneously adding ammonia water or the like and vigorous stirring, or a method of adjusting the pH at which the oxide precursor starts to precipitate by adding hydrogen peroxide or the like. After that, there is a method of depositing a precipitate with aqueous ammonia. Also, the time required for neutralization with ammonia water, etc. should be sufficiently long, preferably 10 minutes or more, or a buffer that neutralizes stepwise while monitoring the pH or maintains a predetermined pH. There is a method of adding a solution.
【００３０】沈殿を生成する過程において、常に1000／
秒以上のせん断速度で撹拌することが望ましい。これに
より生成する酸化物前駆体の粒径を微細化することがで
き、複合酸化物の粒径をより小さくすることができる。
なお酸化物前駆体の粒径は３μｍ以下とすることが望ま
しい。粒径がこれより大きくなると、生成する複合酸化
物の粒径が大きくなりすぎて比表面積の低下により活性
が低下してしまう。In the process of producing a precipitate, 1000 /
It is desirable to stir at a shear rate of at least seconds. As a result, the particle size of the produced oxide precursor can be made finer, and the particle size of the composite oxide can be made smaller.
The particle size of the oxide precursor is preferably 3 μm or less. If the particle size is larger than this, the particle size of the produced composite oxide becomes too large and the specific surface area decreases, resulting in a decrease in activity.
【００３１】この製造方法で得られた複合酸化物は、一
般に平均直径50nm以下の微粒子状をなすCeO2及びZrO2が
凝集した平均粒径が20μｍ以下の凝集粒子からなり、Ce
O2とZrO2は少なくとも一部が固溶体を形成している。The composite oxide obtained by this production method is generally composed of agglomerated particles having an average diameter of 20 μm or less in which fine particles of CeO 2 and ZrO 2 having an average diameter of 50 nm or less are aggregated.
At least a part of O 2 and ZrO 2 forms a solid solution.
【００３２】本発明の製造方法において、沈殿物の焼成
前に、水又は水を含む溶液を分散媒とした懸濁状態また
は系内に水が充分に存在する状態で、沈殿物の熟成処理
を行うことが望ましい。この熟成処理を行うことによっ
て、得られる複合酸化物の粒径が揃えられるため、粒成
長の駆動力の一つである表面分圧が揃い、還元処理時の
粒成長をさらに抑制することができる。In the production method of the present invention, before calcination of the precipitate, aging treatment of the precipitate is carried out in a suspension state using water or a solution containing water as a dispersion medium or in a state where water is sufficiently present in the system. It is desirable to do. By performing this aging treatment, the grain sizes of the obtained composite oxide are made uniform, so that the surface partial pressure, which is one of the driving forces for grain growth, is made uniform and the grain growth during the reduction treatment can be further suppressed. .
【００３３】熟成処理は、系内に水分が充分に存在して
いる状態で、沈殿を含む溶液ごとオートクレーブなどの
耐圧、耐熱容器中で加熱して行い、その後溶媒を蒸発さ
せ、焼成することで行うことができる。あるいは濾別さ
れた沈殿物を水蒸気の存在下で焼成してもよい。この場
合は、飽和水蒸気雰囲気で焼成することが好ましく、10
0〜 200℃で、さらに好ましくは 100〜 150℃で行う水
熱処理が特に望ましい。 100℃未満の加温では熟成の促
進効果が小さく、熟成に要する時間が長大となる。また
200℃より高い温度では、10気圧以上に耐えうる合成装
置が必要となり、設備コストが高くなる。The aging treatment is carried out by heating the whole solution containing the precipitate in a pressure-resistant and heat-resistant container such as an autoclave in a state where water is sufficiently present in the system, and then evaporating the solvent and baking it. It can be carried out. Alternatively, the filtered precipitate may be calcined in the presence of steam. In this case, it is preferable to fire in a saturated steam atmosphere,
A hydrothermal treatment carried out at 0 to 200 ° C, more preferably 100 to 150 ° C is particularly desirable. If the heating temperature is lower than 100 ° C, the aging-promoting effect is small and the aging time becomes long. Also
At temperatures higher than 200 ° C, a synthesizing device capable of withstanding 10 atm or more is required, resulting in high facility cost.
【００３４】上記した熟成処理を行った場合には、加温
の熱によって溶解・再析出が促進されるとともに粒子の
成長が生じる。この場合は、酸塩の全てを中和できる当
量以上の塩基で中和することが望ましい。これにより酸
化物前駆体がより均一に熟成され、細孔が効果的に形成
されるとともに、CeO2−ZrO2固溶体の生成がさらに促進
される。When the above-mentioned aging treatment is carried out, the heat of heating promotes the dissolution and reprecipitation and the growth of particles. In this case, it is desirable to neutralize all of the acid salt with an equivalent amount or more of a base capable of neutralizing the acid salt. As a result, the oxide precursor is aged more uniformly, the pores are effectively formed, and the production of the CeO 2 —ZrO 2 solid solution is further promoted.
【００３５】本発明の特色をなす還元処理は、上記で得
られた複合酸化物を還元性雰囲気中にて 800〜1200℃で
加熱保持することで行う。加熱保持温度が 800℃より低
いとパイロクロア相の生成が困難となり OSCが低下す
る。また1200℃より高くなると比表面積の低下が著しい
ため好ましくない。加熱保持温度を 800〜1200℃とする
ことで、CeとZrが規則配列したパイロクロア相をもち高
い比表面積をもつ本発明の複合酸化物が得られる。The reduction treatment, which is a feature of the present invention, is carried out by heating and holding the composite oxide obtained above in a reducing atmosphere at 800 to 1200 ° C. If the heating and holding temperature is lower than 800 ℃, it becomes difficult to form the pyrochlore phase and the OSC decreases. On the other hand, when the temperature is higher than 1200 ° C, the specific surface area is significantly decreased, which is not preferable. By setting the heating and holding temperature to 800 to 1200 ° C., the composite oxide of the present invention having a pyrochlore phase in which Ce and Zr are regularly arranged and having a high specific surface area can be obtained.
【００３６】そして還元処理される複合酸化物は、CeO2
及びZrO2と反応しない金属酸化物がCeO2−ZrO2複合酸化
物の間に介在しているので、 800〜1200℃という高温で
還元処理を行っても還元処理の間の粒成長が抑制され
る。そのため得られた複合酸化物は、高い比表面積を有
するとともに、CeとZrが規則配列したパイロクロア相を
有している。The composite oxide to be reduced is CeO 2
In addition, since a metal oxide that does not react with ZrO 2 is present between the CeO 2 -ZrO 2 composite oxides, grain growth during the reduction treatment is suppressed even when the reduction treatment is performed at a high temperature of 800 to 1200 ° C. It Therefore, the obtained composite oxide has a high specific surface area and a pyrochlore phase in which Ce and Zr are regularly arranged.
【００３７】還元性雰囲気は、不活性ガス雰囲気又は非
酸化性雰囲気とすることもできるが、H2，COなどの還元
性ガスを積極的に含む雰囲気とすることが望ましい。還
元性ガスを含まないと、結晶格子からの酸素原子の脱離
が充分に速く進行しないためパイロクロア相が充分に生
成できず、高い OSCが得られない場合がある。The reducing atmosphere may be an inert gas atmosphere or a non-oxidizing atmosphere, but it is desirable that the reducing atmosphere be positively containing a reducing gas such as H 2 or CO. If the reducing gas is not included, the desorption of oxygen atoms from the crystal lattice does not proceed sufficiently fast, so the pyrochlore phase cannot be sufficiently generated, and high OSC may not be obtained.
【００３８】さらに本発明の排ガス浄化用助触媒は、本
発明の複合酸化物を担体とし、それに貴金属を担持して
なる。貴金属としては、Pt，Rh，Pd，Ir，Ruなどから一
種又は複数種選択して用いることができ、その担持量は
従来の排ガス浄化用助触媒と同様でよい。また担持方法
も、吸着担持法、吸水担持法など従来の担持法を利用す
ることができる。Further, the exhaust gas purifying co-catalyst of the present invention comprises the composite oxide of the present invention as a carrier, on which a noble metal is supported. As the noble metal, one or more selected from Pt, Rh, Pd, Ir, Ru, etc. can be selected and used, and the supported amount thereof may be the same as that of the conventional exhaust gas purifying promoter. As the supporting method, a conventional supporting method such as an adsorption supporting method or a water absorption supporting method can be used.
【００３９】そして本発明の排ガス浄化用助触媒では、
高温耐久後も担体の比表面積が大きく、しかもCeとZrが
規則配列したパイロクロア相を有しているので、高温耐
久後も高い OSCを有しきわめて触媒化した高い活性を示
す。Then, in the exhaust gas purifying promoter of the present invention,
Even after high-temperature durability, the carrier has a large specific surface area, and since it has a pyrochlore phase in which Ce and Zr are regularly arranged, it has a high OSC even after high-temperature durability and exhibits a high catalytic activity.
【００４０】[0040]
【実施例】以下、実施例及び比較例により本発明を具体
的に説明する。EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.
【００４１】（実施例１）所定濃度の硝酸セリウム（II
I）の水溶液と、所定濃度のオキシ硝酸ジルコニルの水
溶液及び所定濃度の硝酸アルミニウムの水溶液をそれぞ
れ調製し、この３種の水溶液とセリウムイオンの 1.1倍
モルのH2O2を含む過酸化水素水を混合して充分に撹拌し
た。(Example 1) Cerium nitrate (II
An aqueous solution of I), an aqueous solution of zirconyl oxynitrate having a predetermined concentration and an aqueous solution of aluminum nitrate having a predetermined concentration are prepared, respectively, and these three types of aqueous solutions and hydrogen peroxide solution containing 1.1 times mole H 2 O 2 of cerium ions are prepared. And mixed well.
【００４２】この混合水溶液に全ての硝酸根を中和でき
る量の 1.2倍モルの NH3を含むアンモニア水を添加し、
メカニカルスターラー及びホモジナイザで１時間撹拌し
た。ホモジナイザによれば、 1000／秒以上のせん断速
度で撹拌される。得られた共沈物（酸化物前駆体）を濾
過・洗浄し、大気中にて 300℃で３時間乾燥し、さらに
500℃で１時間焼成した。Ammonia water containing 1.2 times the molar amount of NH 3 capable of neutralizing all nitrate radicals was added to this mixed aqueous solution,
Stir for 1 hour with a mechanical stirrer and homogenizer. According to the homogenizer, stirring is performed at a shear rate of 1000 / sec or more. The obtained coprecipitate (oxide precursor) is filtered and washed, dried in air at 300 ° C. for 3 hours, and further
It was baked at 500 ° C. for 1 hour.
【００４３】得られた酸化物粉末を、H2を５％含むN2気
流中にて1000℃で５時間還元処理し、大気中にて 500℃
で１時間処理して、本発明の複合酸化物粉末を調製し
た。この複合酸化物粉末の比表面積をN2吸着を用いた B
ET法（１点法）により測定し、結果を表１に示す。The obtained oxide powder was subjected to reduction treatment in an N 2 stream containing 5% of H 2 at 1000 ° C. for 5 hours and then in the atmosphere at 500 ° C.
For 1 hour to prepare the composite oxide powder of the present invention. The specific surface area of this complex oxide powder was determined using N 2 adsorption B
The measurement was performed by the ET method (1-point method), and the results are shown in Table 1.
【００４４】次に、得られた複合酸化物粉末に所定濃度
のジニトロジアミン白金水溶液の所定量を含浸させ、蒸
発乾固後 300℃で３時間焼成してPtを担持して本発明の
助触媒粉末を調製した。Ptの担持量は１重量％である。Next, the obtained composite oxide powder is impregnated with a predetermined amount of an aqueous solution of dinitrodiamine platinum having a predetermined concentration, evaporated to dryness, and calcined at 300 ° C. for 3 hours to support Pt to carry the promoter of the present invention. A powder was prepared. The loading amount of Pt is 1% by weight.
【００４５】この助触媒粉末15mgを秤量し、H2を10％含
むN2ガスと、O2を５％含むN2ガスとを交互に流しなが
ら、 500℃における熱重量分析を行って重量の減少量と
増加量を測定した。そして両者の測定値から相当する酸
素吸放出量を算出し、結果を表１に示す。また得られた
複合酸化物粉末のＸ線回折チャートを図１に示す。[0045] Weigh the cocatalyst powder 15 mg, and N 2 gas containing H 2 10%, while flowing the N 2 gas containing O 2 5% alternatively, the weight subjected to thermal gravimetric analysis at 500 ° C. Decrease and increase were measured. Then, the corresponding oxygen storage / release amount was calculated from the measured values of both, and the results are shown in Table 1. The X-ray diffraction chart of the obtained composite oxide powder is shown in FIG.
【００４６】（実施例２）実施例１と同様にして得られ
た共沈物を、濾過する前に 0.12MPa， 110℃の条件で２
時間水熱処理したこと以外は実施例１と同様にして酸化
物粉末を得た。この酸化物粉末を用いたこと以外は実施
例１と同様に還元処理して複合酸化物粉末を調製し、同
様にPtを担持して助触媒粉末を調製した。(Example 2) The coprecipitate obtained in the same manner as in Example 1 was filtered under conditions of 0.12 MPa and 110 ° C before filtration.
An oxide powder was obtained in the same manner as in Example 1 except that the hydrothermal treatment was performed for an hour. A reduction treatment was carried out in the same manner as in Example 1 except that this oxide powder was used to prepare a composite oxide powder, and similarly Pt was carried to prepare a cocatalyst powder.
【００４７】得られた複合酸化物粉末の比表面積と助触
媒粉末の酸素吸放出量を実施例１と同様に測定し、結果
を表１に示す。また得られた複合酸化物粉末のＸ線回折
チャートを図２に示す。The specific surface area of the obtained composite oxide powder and the oxygen absorption / release amount of the promoter powder were measured in the same manner as in Example 1, and the results are shown in Table 1. The X-ray diffraction chart of the obtained composite oxide powder is shown in FIG.
【００４８】（比較例１）還元処理を行わなかったこと
以外は実施例１と同様にして複合酸化物粉末を調製し、
同様にPtを担持して助触媒粉末を調製した。(Comparative Example 1) A composite oxide powder was prepared in the same manner as in Example 1 except that no reduction treatment was carried out.
Similarly, Pt was supported to prepare a promoter powder.
【００４９】得られた複合酸化物粉末の比表面積と助触
媒粉末の酸素吸放出量を実施例１と同様に測定し、結果
を表１に示す。また得られた複合酸化物粉末のＸ線回折
チャートを図３に示す。The specific surface area of the obtained composite oxide powder and the oxygen absorption / release amount of the promoter powder were measured in the same manner as in Example 1, and the results are shown in Table 1. The X-ray diffraction chart of the obtained composite oxide powder is shown in FIG.
【００５０】（比較例２）硝酸アルミニウムを用いなか
ったこと以外は実施例１と同様にして複合酸化物粉末を
調製し、同様にPtを担持して助触媒粉末を調製した。Comparative Example 2 A composite oxide powder was prepared in the same manner as in Example 1 except that aluminum nitrate was not used, and Pt was similarly carried to prepare a cocatalyst powder.
【００５１】得られた複合酸化物粉末の比表面積と助触
媒粉末の酸素吸放出量を実施例１と同様に測定し、結果
を表１に示す。また得られた複合酸化物粉末のＸ線回折
チャートを図１に示す。The specific surface area of the obtained composite oxide powder and the oxygen absorption / release amount of the promoter powder were measured in the same manner as in Example 1, and the results are shown in Table 1. The X-ray diffraction chart of the obtained composite oxide powder is shown in FIG.
【００５２】＜評価＞<Evaluation>
【００５３】[0053]
【表１】 [Table 1]
【００５４】図１〜４から、実施例１，２及び比較例２
の複合酸化物では、比較例１には見られないパイロクロ
ア相に帰属するピーク（２θ＝37゜）が観察される。From FIGS. 1 to 4, Examples 1 and 2 and Comparative Example 2
In the composite oxide of No. 1, a peak (2θ = 37 °) attributed to the pyrochlore phase, which is not seen in Comparative Example 1, is observed.
【００５５】そして表１より、比較例１の複合酸化物及
び助触媒は、実施例１，２及び比較例２に比べて比表面
積は著しく高いものの OSCが低いことがわかる。すなわ
ち比較例１では、還元処理を行わなかったために粒成長
が生じていないものの、パイロクロア相が生成しなかっ
たために充分な OSCが発現しなかったと考えられる。From Table 1, it can be seen that the composite oxides and cocatalysts of Comparative Example 1 have a significantly higher specific surface area than those of Examples 1 and 2 and Comparative Example 2, but have a low OSC. That is, in Comparative Example 1, although no grain growth occurred because no reduction treatment was performed, it is considered that sufficient OSC was not expressed because no pyrochlore phase was generated.
【００５６】しかし実施例１，２では、比表面積は比較
例１ほど高くないものの、比較例１より高い OSCを示
し、これは還元処理に伴う比表面積の低下分を補うだけ
の活性がパイロクロア相の生成によって得られたためと
考えられる。However, in Examples 1 and 2, although the specific surface area was not as high as that of Comparative Example 1, it showed higher OSC than that of Comparative Example 1. This is because the activity to compensate for the decrease in specific surface area due to the reduction treatment is the pyrochlore phase. It is thought that this is because it was obtained by the generation of
【００５７】また比較例２の複合酸化物は、実施例１，
２及び比較例１に比べて比表面積が著しく低い。これは
Al2O3が介在しない複合酸化物を還元処理したことによ
って粒成長が生じたためと認められる。そのため比較例
２の触媒ではパイロクロア相を含むにも関わらず実施例
１，２よりも OSCが低くなっている。The composite oxide of Comparative Example 2 is the same as that of Example 1.
2 has a remarkably low specific surface area as compared with 2 and Comparative Example 1. this is
It is considered that grain growth occurred due to the reduction treatment of the composite oxide without Al 2 O 3 intervening. Therefore, the OSC of the catalyst of Comparative Example 2 was lower than that of Examples 1 and 2 even though the catalyst contained the pyrochlore phase.
【００５８】さらに実施例２は実施例１より高い比表面
積と OSCを示し、複合酸化物の製造時に水熱処理を行う
ことが望ましいこともわかる。Further, Example 2 shows a higher specific surface area and OSC than Example 1, and it is also understood that it is desirable to carry out hydrothermal treatment during the production of the composite oxide.
【００５９】[0059]
【発明の効果】すなわち本発明の複合酸化物及び助触媒
によれば、高温処理後でも高い比表面積と高い OSCを両
立させることができ、これを用いた触媒は高い浄化活性
を発現する。また本発明の製造方法によれば、本発明の
複合酸化物を容易かつ確実に製造することができる。[Effects of the Invention] That is, according to the composite oxide and co-catalyst of the present invention, both a high specific surface area and a high OSC can be achieved even after high-temperature treatment, and a catalyst using this exhibits high purification activity. Further, according to the production method of the present invention, the composite oxide of the present invention can be easily and reliably produced.
【図面の簡単な説明】[Brief description of drawings]
【図１】実施例１の複合酸化物のＸ線回折チャートであ
る。FIG. 1 is an X-ray diffraction chart of the composite oxide of Example 1.
【図２】実施例２の複合酸化物のＸ線回折チャートであ
る。FIG. 2 is an X-ray diffraction chart of the composite oxide of Example 2.
【図３】比較例１の複合酸化物のＸ線回折チャートであ
る。FIG. 3 is an X-ray diffraction chart of the composite oxide of Comparative Example 1.
【図４】比較例２の複合酸化物のＸ線回折チャートであ
る。FIG. 4 is an X-ray diffraction chart of the composite oxide of Comparative Example 2.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ テーマコート゛(参考） Ｂ０１Ｊ 37/03 Ｂ０１Ｊ 37/16 37/10 Ｃ０１Ｇ 1/02 37/16 Ｆ０１Ｎ 3/10 Ａ Ｃ０１Ｇ 1/02 3/28 ３０１Ａ Ｆ０１Ｎ 3/10 ３０１Ｐ 3/28 ３０１ Ｂ０１Ｄ 53/36 ＺＡＢＣ Ｂ０１Ｊ 23/56 ３０１Ａ (72)発明者 田辺 稔貴 愛知県愛知郡長久手町大字長湫字横道41番 地の１株式会社豊田中央研究所内 (72)発明者 鈴木 正 愛知県愛知郡長久手町大字長湫字横道41番 地の１株式会社豊田中央研究所内 (72)発明者 須田 明彦 愛知県愛知郡長久手町大字長湫字横道41番 地の１株式会社豊田中央研究所内 Ｆターム(参考） 3G091 AA02 AB03 BA07 BA39 GB01X GB04X GB05W GB06W GB07W GB10X GB17X 4D048 AA06 AA13 AA18 AB05 BA03X BA06Y BA07Y BA08X BA18Y BA19X BA30X BA31Y BA32Y BA33Y BA42X BB01 EA04 4G048 AA03 AB02 AB05 AC08 AD06 AE05 4G069 AA01 AA03 AA08 BA01A BA01B BA02A BA04A BA05A BA05B BB02A BB06A BB06B BC16A BC38A BC42A BC43A BC43B BC51A BC69A BC75B CA03 CA09 EA01Y EC02Y EC22X EC22Y EC25 FA01 FB10 FB30 FB44 FC07 ─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. 7 Identification code FI theme code (reference) B01J 37/03 B01J 37/16 37/10 C01G 1/02 37/16 F01N 3/10 A C01G 1/02 3/28 301A F01N 3/10 301P 3/28 301 B01D 53/36 ZABC B01J 23/56 301A (72) Inventor Minoru Tanabe 1 Toyota 41 Chuo, Nagakute-cho, Aichi-gun, Aichi Inside the research institute (72) Inventor Masa Tadashi, Nagachite-cho, Aichi-gun, Aichi Prefecture 1 41, Yokoshiro, Yokota Central Research Institute Co., Ltd. (72) Inventor, Akihiko Suda, Aichi-gun, Nagakute, Aichi-gun, 41 No.1 F-term in Toyota Central Research Institute Co., Ltd. (reference) 3G091 AA02 AB03 BA07 BA39 GB01X GB04X GB05W GB06W GB07W GB10X GB17X 4D048 AA06 AA13 AA18 AB05 BA03 X BA06Y BA07Y BA08X BA18Y BA19X BA30X BA31Y BA32Y BA33Y BA42X BB01 EA04 4G048 AA03 AB02 AB05 AC08 AD06 AE05 4G0BC ABCBA25ABC BC02 BC01 CA01 BC01BC01 BC22 BC02 BC02 BC01 BC02 BC02 BC02 BC01 BC22 BC02 BC02 BC01 BC01 BC22 BC02 BC01 BC25 BC02 BC01 BC25 BC02 BC01 BC01 BC01 BC25 BC02 BC01 BC01 BC01 BC25 BC02 BC01 BC01 BC01 BC25 BC02 BC01 BC01 BC01 BC01 BC25 BC02 BC01 BC01 BC01 BC25 BC02 BC01 FB30 FB44 FC07
Claims (7)
ない金属酸化物との複合酸化物からなり、Ce及びZrが規
則配列したパイロクロア相をもつことを特徴とする複合
酸化物。1. A complex oxidation comprising a complex oxide of CeO 2 , ZrO 2, and a metal oxide that does not react with CeO 2 and ZrO 2, and having a pyrochlore phase in which Ce and Zr are regularly arranged. object.
溶した固溶体を形成している請求項１に記載の複合酸化
物。2. The complex oxide according to claim 1, wherein CeO 2 and ZrO 2 at least partially form a solid solution with each other.
物は Al2O3である請求項１に記載の複合酸化物。3. The composite oxide according to claim 1, wherein the metal oxide that does not react with CeO 2 and ZrO 2 is Al 2 O 3 .
と、酸化物がCeO2及びZrO2と反応しない金属の化合物の
溶液に沈殿剤を添加して共沈法により沈殿物を生成し、
該沈殿物を焼成した後、還元性雰囲気中にて 800〜1200
℃で加熱保持する還元処理を行うことを特徴とする複合
酸化物の製造方法。4. A precipitation agent is added to a solution of a cerium compound, a zirconium compound, and a compound of a metal whose oxide does not react with CeO 2 and ZrO 2 to form a precipitate by a coprecipitation method,
800 ~ 1200 in reducing atmosphere after baking the precipitate
A method for producing a composite oxide, which comprises performing a reduction treatment of heating and holding at ℃.
溶液を分散媒とした懸濁状態または系内に水が充分に存
在する状態で沈殿物の熟成処理を行う請求項４に記載の
複合酸化物の製造方法。5. The aging treatment of the precipitate is carried out before the precipitation is calcined in a suspension state using water or a solution containing water as a dispersion medium or in a state where water is sufficiently present in the system. A method for producing the composite oxide described.
び 100〜 200℃の温度で処理する水熱処理である請求項
５に記載の複合酸化物の製造方法。6. The method for producing a composite oxide according to claim 5, wherein the aging treatment is a hydrothermal treatment performed at a pressure of 0.11 to 0.2 MPa and a temperature of 100 to 200 ° C.
複合酸化物に貴金属を担持してなることを特徴とする排
ガス浄化用助触媒。7. An exhaust gas purifying co-catalyst, comprising a noble metal supported on the composite oxide according to claim 1.
Priority Applications (4)
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|---|---|---|---|
| JP2001261260A JP4352300B2 (en) | 2001-08-30 | 2001-08-30 | Composite oxide, method for producing the same, and co-catalyst for exhaust gas purification |
| EP02018807A EP1287876B1 (en) | 2001-08-30 | 2002-08-22 | Composite oxide, process for producing the same, and exhaust gas reducing co-catalyst |
| DE60211260T DE60211260T2 (en) | 2001-08-30 | 2002-08-22 | Mixed oxide, process for its preparation and exhaust gas reduction CO catalyst |
| US10/225,186 US7247597B2 (en) | 2001-08-30 | 2002-08-22 | Composite oxide, process for producing the same, and exhaust gas reducing co-catalyst |
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| JP2001261260A JP4352300B2 (en) | 2001-08-30 | 2001-08-30 | Composite oxide, method for producing the same, and co-catalyst for exhaust gas purification |
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