JP2001009279A - Catalyst for purification of exhaust gas, its production and method for purifying exhaust gas - Google Patents
Catalyst for purification of exhaust gas, its production and method for purifying exhaust gasInfo
- Publication number
- JP2001009279A JP2001009279A JP11183155A JP18315599A JP2001009279A JP 2001009279 A JP2001009279 A JP 2001009279A JP 11183155 A JP11183155 A JP 11183155A JP 18315599 A JP18315599 A JP 18315599A JP 2001009279 A JP2001009279 A JP 2001009279A
- Authority
- JP
- Japan
- Prior art keywords
- exhaust gas
- catalyst
- titania
- alumina
- storage material
- 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
- 239000003054 catalyst Substances 0.000 title claims abstract description 76
- 238000000746 purification Methods 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims description 17
- 238000004519 manufacturing process Methods 0.000 title claims description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 127
- 239000002245 particle Substances 0.000 claims abstract description 63
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 56
- 239000011232 storage material Substances 0.000 claims abstract description 29
- 239000007789 gas Substances 0.000 claims description 58
- 239000000843 powder Substances 0.000 claims description 45
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 40
- 229910010413 TiO 2 Inorganic materials 0.000 claims description 34
- 239000000446 fuel Substances 0.000 claims description 17
- 239000002002 slurry Substances 0.000 claims description 14
- 239000010419 fine particle Substances 0.000 claims description 13
- 229910000510 noble metal Inorganic materials 0.000 claims description 13
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 8
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 8
- 239000000758 substrate Substances 0.000 claims description 8
- 229910052783 alkali metal Inorganic materials 0.000 claims description 7
- 150000001340 alkali metals Chemical class 0.000 claims description 7
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 239000003513 alkali Substances 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 claims description 2
- 238000002485 combustion reaction Methods 0.000 claims 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract description 13
- 229910052717 sulfur Inorganic materials 0.000 abstract description 13
- 239000011593 sulfur Substances 0.000 abstract description 13
- 231100000572 poisoning Toxicity 0.000 abstract description 9
- 230000000607 poisoning effect Effects 0.000 abstract description 9
- 239000011248 coating agent Substances 0.000 abstract description 5
- 238000000576 coating method Methods 0.000 abstract description 5
- 238000003795 desorption Methods 0.000 abstract description 5
- 239000002243 precursor Substances 0.000 abstract description 3
- 230000007774 longterm Effects 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 14
- 238000003860 storage Methods 0.000 description 12
- 238000012937 correction Methods 0.000 description 9
- 239000008188 pellet Substances 0.000 description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 239000002131 composite material Substances 0.000 description 6
- 238000000635 electron micrograph Methods 0.000 description 5
- 229910052697 platinum Inorganic materials 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 230000002776 aggregation Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000010948 rhodium Substances 0.000 description 4
- 229920006395 saturated elastomer Polymers 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- 238000004220 aggregation Methods 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000002585 base Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 238000010907 mechanical stirring Methods 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical class [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 2
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 102100033041 Carbonic anhydrase 13 Human genes 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910052692 Dysprosium Inorganic materials 0.000 description 1
- 101000867860 Homo sapiens Carbonic anhydrase 13 Proteins 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
- 229910052769 Ytterbium Inorganic materials 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- IXSUHTFXKKBBJP-UHFFFAOYSA-L azanide;platinum(2+);dinitrite Chemical compound [NH2-].[NH2-].[Pt+2].[O-]N=O.[O-]N=O IXSUHTFXKKBBJP-UHFFFAOYSA-L 0.000 description 1
- ITHZDDVSAWDQPZ-UHFFFAOYSA-L barium acetate Chemical compound [Ba+2].CC([O-])=O.CC([O-])=O ITHZDDVSAWDQPZ-UHFFFAOYSA-L 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- -1 nitrate ions Chemical class 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000002574 poison Substances 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は自動車の排気系など
に装着されて用いられるNOx 吸蔵還元型の排ガス浄化用
触媒とその製造方法、及びその排ガス浄化用触媒を用い
た排ガス浄化方法に関する。The present invention relates to the NO x storage-and-reduction type method the exhaust gas purifying catalyst and its preparation for use is mounted such in the exhaust system of an automobile, and an exhaust gas purifying method using the exhaust gas purifying catalyst.
【０００２】[0002]
【従来の技術】リーンバーンエンジンにおいて、常時は
酸素過剰の燃料リーン条件で燃焼させ、間欠的に燃料ス
トイキ〜リッチ条件とすることにより排ガスを還元雰囲
気としてNOx を還元浄化するシステムが開発され、実用
化されている。そしてこのシステムに最適な排ガス浄化
用触媒として、リーン雰囲気でNOx を吸蔵し、ストイキ
〜リッチ雰囲気で吸蔵されたNOx を放出するNOx 吸蔵材
を用いたNOx 吸蔵還元型の排ガス浄化用触媒が開発され
ている。BACKGROUND ART In a lean-burn engine, normally is burned with oxygen excess fuel lean condition, the system reduces and purifies NO x exhaust gas as a reducing atmosphere is developed by the intermittent fuel stoichiometric-rich condition, Has been put to practical use. And as the best catalyst for purification of exhaust gas in the system, occludes NO x in lean atmosphere, an exhaust gas purification of the NO x storage reduction using the NO x storage material that releases NO x occluded in the stoichiometric-rich atmosphere Catalysts are being developed.
【０００３】例えば特開平5-317652号公報には、Baなど
のアルカリ土類金属とPtをアルミナなどの多孔質酸化物
担体に担持した排ガス浄化用触媒が提案されている。ま
た特開平 6-31139号公報には、Ｋなどのアルカリ金属と
Ptをアルミナなどの多孔質酸化物担体に担持した排ガス
浄化用触媒が提案されている。さらに特開平5-168860号
公報には、Laなどの希土類元素とPtをアルミナなどの多
孔質酸化物担体に担持した排ガス浄化用触媒が提案され
ている。For example, Japanese Patent Application Laid-Open No. 5-317652 proposes an exhaust gas purifying catalyst in which an alkaline earth metal such as Ba and Pt are supported on a porous oxide carrier such as alumina. Also, JP-A-6-31139 discloses that an alkali metal such as K is used.
An exhaust gas purifying catalyst in which Pt is supported on a porous oxide carrier such as alumina has been proposed. Further, Japanese Patent Application Laid-Open No. H5-168860 proposes an exhaust gas purifying catalyst in which a rare earth element such as La and Pt are supported on a porous oxide carrier such as alumina.
【０００４】空燃比を燃料リーン側からパルス状に燃料
ストイキ〜リッチ側となるように制御することにより、
排ガスもリーン雰囲気からパルス状にストイキ〜リッチ
雰囲気となるので、このNOx 吸蔵還元型触媒を用いれ
ば、リーン側ではNOx がNOx 吸蔵材に吸蔵され、それが
ストイキ又はリッチ側で放出されてHCやCOなどの還元性
成分と反応して浄化される。したがって、リーンバーン
エンジンからの排ガスであってもNOx を効率良く浄化す
ることができる。また排ガス中のHC及びCOは、貴金属に
より酸化されるとともにNOx の還元に消費されるので、
HC及びCOも効率よく浄化される。By controlling the air-fuel ratio from the fuel lean side to the fuel stoichiometric to rich side in a pulsed manner,
Since the exhaust gas becomes stoichiometric-rich atmosphere in pulses from a lean atmosphere, the use of this NO x storage-and-reduction type catalyst, NO x is occluded in the NO x storage material in the lean side, it is released in stoichiometric or rich side And reacts with reducing components such as HC and CO to be purified. Therefore, it is possible to efficiently purify the NO x be a exhaust gas from a lean burn engine. The HC and CO in the exhaust gas, since it is consumed in the reduction of the NO x while being oxidized by the noble metal,
HC and CO are also efficiently purified.
【０００５】ところが排ガス中には、燃料中に含まれる
硫黄（Ｓ）が燃焼して生成したSO2が含まれ、それがリ
ーン雰囲気の排ガス中で貴金属により酸化されてSO3 と
なる。そしてそれがやはり排ガス中に含まれる水蒸気に
より容易に硫酸となり、これらがNOx 吸蔵材と反応して
亜硫酸塩や硫酸塩が生成し、これによりNOx 吸蔵材が被
毒劣化することが明らかとなった。また、アルミナなど
の多孔質酸化物担体はSOx を吸着しやすいという性質が
あることから、上記硫黄被毒が促進されるという問題が
ある。However, the exhaust gas contains SO 2 generated by burning sulfur (S) contained in the fuel, which is oxidized by a noble metal into SO 3 in the exhaust gas in a lean atmosphere. And it will be readily sulfate by water vapor also contained in the exhaust gas, these sulfites and sulfates are produced by the reaction with the NO x storage material, thereby the NO x storage material it would degrade poisoned became. The porous oxide support such as alumina from the the property that easily adsorbs SO x, there is a problem that the sulfur poisoning is facilitated.
【０００６】そして、このようにNOx 吸蔵材が亜硫酸塩
や硫酸塩となって被毒劣化すると、もはやNOx を吸蔵す
ることができなくなり、その結果上記触媒では、耐久試
験後（以下、耐久後という）のNOx の浄化性能が低下す
るという不具合があった。[0006] When thus the NO x storage material is deteriorated poisoning become sulfites and sulfates, it becomes impossible to occlude NO x longer, with the result the catalyst after the durability test (hereinafter, durable purification performance of the NO x in) that after there has been a problem of a decrease.
【０００７】また、チタニア担体を用いることが想起さ
れ実験が行われた。その結果、SOxはチタニアには吸着
されずそのまま下流に流れ、また貴金属と直接接触した
SO2のみが酸化されるので、硫黄被毒の程度は少ないこ
とが明らかとなった。ところがチタニア担体では初期活
性が低く、耐久後のNOx の浄化性能も低いままであると
いう不具合があることも明らかとなった。[0007] Further, an experiment was conducted in which the use of a titania carrier was recalled. As a result, SO x flowed downstream as it was without being adsorbed by titania, and came in direct contact with precious metals
Since only SO 2 was oxidized, it was revealed that the degree of sulfur poisoning was small. However, it has also been found that the titania carrier has a problem that the initial activity is low and the NO x purification performance after durability remains low.
【０００８】そこで特開平8-099034号公報には、TiO2-A
l2O3よりなる複合担体を用いることが提案されている。
また本願出願人は、特願平9-359690において、ルチル型
のチタニアをアルミナに添加した担体を用いることを提
案している。Therefore, Japanese Patent Application Laid-Open No. Hei 8-099034 discloses that TiO 2 -A
It has been proposed to use a composite carrier consisting of l 2 O 3 .
In addition, the applicant of the present application has proposed in Japanese Patent Application No. 9-359690 that a carrier obtained by adding rutile-type titania to alumina is used.
【０００９】このようにアルミナとチタニアとを混合あ
るいは複合酸化物とした複合担体を用いることで、アル
ミナの長所により初期のNOx 浄化率を高く維持すること
ができる。またチタニアは、アルミナに比べてSOx を吸
着しにくく、かつチタニアに吸着されたSOx はアルミナ
に吸着された場合に比べて低温で脱離しやすいので、NO
x 吸蔵材とSOx との接触確率が低くなる。したがって上
記複合担体を用いると、初期においても高いNOx 浄化率
が確保され、硫黄被毒が抑制されるため耐久後のNOx 浄
化率が向上する。[0009] may be maintained in this way by using the composite support was alumina and titania and mixtures or complex oxides, high initial of the NO x purification rate by virtue of the alumina. The titania difficult to adsorb SO x in comparison with the alumina, and so easily desorbed at a lower temperature than in the case SO x adsorbed on the titania adsorbed on alumina, NO
The probability of contact between the x storage material and SO x is reduced. Therefore, when the composite carrier is used, a high NO x purification rate is secured even at the initial stage, and sulfur poisoning is suppressed, so that the NO x purification rate after durability is improved.
【００１０】[0010]
【発明が解決しようとする課題】ところが、上記特開平
8-099034号公報などに開示されているような担体にチタ
ニアを含む排ガス浄化用触媒であっても、高温耐久後の
硫黄被毒の抑制効果は十分とはいえず、さらなる硫黄被
毒の抑制とNOx 浄化率の向上が求められている。本発明
はこのような事情に鑑みてなされたものであり、担体に
チタニアを含むNO x 吸蔵還元型の排ガス浄化用触媒の硫
黄被毒をさらに抑制して高温耐久後のNOx浄化率を一層
向上させることを目的とする。However, the above-mentioned Japanese Patent Application Laid-Open
A carrier such as disclosed in JP-A-8-099034
Even exhaust gas purifying catalysts containing near
The effect of suppressing sulfur poisoning is not sufficient.
Poison control and NOxImprovement of the purification rate is required. The present invention
Is made in view of such circumstances,
NO containing titania xOxidation-reduction type exhaust gas purification catalyst sulfur
NO after high-temperature durability by further suppressing yellow poisoningxFurther purification rate
The purpose is to improve.
【００１１】[0011]
【課題を解決するための手段】上記課題を解決する本発
明の排ガス浄化用触媒の特徴は、担体基材と、担体基材
上に形成された多孔質酸化物よりなる触媒担持層と、触
媒担持層に担持された貴金属と、触媒担持層に担持され
たアルカリ金属，アルカリ土類金属及び希土類元素から
選ばれる少なくとも一種のNOx 吸蔵材と、からなるNOx
吸蔵還元型の排ガス浄化用触媒において、触媒担持層に
は、アルミナ粒子の表面を粒子径が10nm以下のそれぞれ
独立したチタニア微粒子で被覆してなるAl2O3-TiO2担体
粉末を含むことにある。The exhaust gas purifying catalyst of the present invention which solves the above-mentioned problems is characterized by a carrier substrate, a catalyst supporting layer formed of a porous oxide formed on the carrier substrate, and a catalyst. a noble metal supported on carrier layer, an alkali metal supported on the catalyst supporting layer, and at least one NO x storage material selected from alkaline earth metals and rare earth elements, made from the NO x
In the storage reduction type exhaust gas purifying catalyst, the catalyst supporting layer contains Al 2 O 3 -TiO 2 carrier powder in which the surface of alumina particles is coated with independent titania fine particles having a particle diameter of 10 nm or less. is there.
【００１２】また上記排ガス浄化用触媒を製造するに最
適な本発明の製造方法の特徴は、アルミナ粒子と粒子径
が10nm以下のチタニアゾルとからなるスラリーのpHを５
未満とする第１工程と、pHが５未満とされたスラリーの
pHを５〜８とすることでアルミナ粒子の表面が粒子径が
10nm以下のそれぞれ独立したチタニア微粒子で被覆され
たAl2O3-TiO2担体粉末を得る第２工程と、Al2O3-TiO2担
体粉末にアルカリ金属，アルカリ土類金属及び希土類元
素から選ばれる少なくとも一種のNOx 吸蔵材と貴金属と
を担持する第３工程と、よりなることにある。A feature of the production method of the present invention, which is most suitable for producing the exhaust gas purifying catalyst, is that the pH of a slurry comprising alumina particles and a titania sol having a particle diameter of 10 nm or less is adjusted to 5 or less.
And the first step of making the pH less than 5
By adjusting the pH to 5 to 8, the surface of the alumina particles has a particle diameter of
A second step of obtaining an Al 2 O 3 -TiO 2 carrier powder coated with independent titania fine particles of 10 nm or less, and selecting the Al 2 O 3 -TiO 2 carrier powder from alkali metals, alkaline earth metals and rare earth elements. a third step of carrying at least one NO x storage material and the noble metal is more becomes possible.
【００１３】そして本発明の排ガス浄化方法の特徴は、
請求項１に記載の排ガス浄化用触媒あるいは請求項２に
記載の製造方法にて製造された排ガス浄化用触媒を、空
燃比（Ａ／Ｆ）が18以上で燃焼された酸素過剰雰囲気の
排ガスと接触させて排ガス中に含まれるNOx をNOx 吸蔵
材に吸蔵し、空燃比を定期的にストイキ〜燃料過剰に変
動させてNOx 吸蔵材から放出されたNOx を還元浄化する
ことにある。The features of the exhaust gas purifying method of the present invention are as follows.
The exhaust gas purifying catalyst according to claim 1 or the exhaust gas purifying catalyst produced by the production method according to claim 2 is combined with an exhaust gas in an oxygen-excess atmosphere burned at an air-fuel ratio (A / F) of 18 or more. the contacted by occluding NO x contained in the exhaust gas to the NO x storage material, regularly in the stoichiometric-fuel excessively varied by reduction purify the released NO x from the NO x storage material of the air-fuel ratio .
【００１４】[0014]
【発明の実施の形態】ルチル型のチタニアをアルミナに
添加した担体を用いたNOx 吸蔵還元型の排ガス浄化用触
媒において、耐久後のNOx 浄化率が期待されたほど向上
しない原因は、アルミナ中へのチタニアの分散性が低い
ためにアルミナにSOx が吸着される確率が高くなり、NO
x 吸蔵材とSOx との反応によって硫酸塩がある程度生成
するため、と考えられた。In the NO x storage-reduction type exhaust gas purifying catalyst of titania PREFERRED EMBODIMENTS rutile with carrier added to the alumina, the cause does not improve as the NO x purification ratio after durability is expected, alumina probability of alumina SO x is adsorbed due to low dispersibility of titania to the medium becomes high, NO
It is considered that the reaction between the x storage material and SO x generates sulfate to some extent.
【００１５】そこで本発明の排ガス浄化用触媒では、ア
ルミナ粒子の表面を粒子径が10nm以下のチタニア微粒子
で被覆してなるAl2O3-TiO2担体粉末を含む触媒担持層を
有している。このような構成とすることにより、耐久後
のNOx 浄化率が向上する。Therefore, the exhaust gas purifying catalyst of the present invention has a catalyst supporting layer containing an Al 2 O 3 —TiO 2 carrier powder obtained by coating the surface of alumina particles with titania fine particles having a particle diameter of 10 nm or less. . With such a structure, thereby improving the NO x purification ratio after the durability test.
【００１６】このようになる原因は明らかではないが、
チタニアは凝集して二次粒子となることなく微細な一次
粒子状態でアルミナ粒子表面を均一に高分散した状態で
被覆しているから、チタニアはアルミナに比べて塩基点
が少なくSOx が吸着し難い、あるいは吸着したSOx が脱
離しやすいので、全体としてSOx の吸着量が低減される
ためと考えられる。さらにはNOx 吸蔵材とアルミナとの
接触が抑制されてチタニアとNOx 吸蔵材との界面が増加
し、これにより分解し易い複合酸化物前駆体が形成され
ること、などの理由により吸着したSOx の脱離が容易と
なるためと考えられる。Although the cause of this is not clear,
Since titania covers the alumina particle surface in a state of fine primary particles without agglomeration into secondary particles in a highly dispersed state, titania has fewer base points than SO and adsorbs SO x. It is considered that the amount of SO x adsorbed is reduced as a whole because it is difficult or the adsorbed SO x is easily desorbed. Furthermore, the contact between the NO x storage material and alumina was suppressed, and the interface between titania and the NO x storage material increased, thereby forming a composite oxide precursor that was easily decomposed, and was adsorbed. This is probably because SO x is easily desorbed.
【００１７】担体基材としては、コージェライトなどの
耐熱性セラミックスあるいは金属から形成されたものを
用いることができ、その形状はハニカム形状のモノリス
型あるいはペレット型などから選択することができる。As the carrier substrate, a substrate made of a heat-resistant ceramic such as cordierite or a metal can be used, and the shape thereof can be selected from a honeycomb monolith type or a pellet type.
【００１８】触媒担持層は、アルミナ粒子の表面を粒子
径が10nm以下のそれぞれ独立したチタニア微粒子で被覆
してなるAl2O3-TiO2担体粉末を含んでいる。アルミナ粒
子としては、耐熱性に優れ比表面積の大きなγ-Al2O3が
特に好適である。このAl2O3-TiO2担体粉末の核となるア
ルミナ粒子の粒径は、これを被覆するチタニア微粒子よ
り大きければ特に制限されない。The catalyst supporting layer contains Al 2 O 3 —TiO 2 carrier powder obtained by coating the surface of alumina particles with independent titania fine particles having a particle diameter of 10 nm or less. As the alumina particles, γ-Al 2 O 3 having excellent heat resistance and a large specific surface area is particularly suitable. The particle size of the alumina particles serving as the nucleus of the Al 2 O 3 —TiO 2 carrier powder is not particularly limited as long as it is larger than the titania particles covering the alumina particles.
【００１９】Al2O3-TiO2担体粉末において、アルミナ粒
子を被覆しているチタニア微粒子の粒径が10nmより大き
くなると、アルミナ粒子にSOx が吸着されやすくなり、
かつチタニアとNOx 吸蔵材との界面が減少して吸着した
SOx の脱離が困難となるため、耐久後のNOx 浄化率が低
下してしまう。In the Al 2 O 3 —TiO 2 carrier powder, when the particle size of the titania fine particles covering the alumina particles is larger than 10 nm, SO x is easily adsorbed on the alumina particles,
And the interface between the titania and the NO x storage material is adsorbed decreased
Since it becomes difficult to desorb SO x , the NO x purification rate after durability decreases.
【００２０】またAl2O3-TiO2担体粉末におけるチタニア
微粒子の被覆量は、重量比で Al2O3／TiO2＝４／１〜１
／４の範囲が望ましい。アルミナがこれより少ないと浄
化性能が低くなるとともに貴金属のシンタリングが生じ
やすくなり、チタニアがこれより少ないと耐硫黄被毒性
が低下する。The coating amount of the titania fine particles in the Al 2 O 3 -TiO 2 carrier powder is such that Al 2 O 3 / TiO 2 = 4/1 to 1 by weight.
A range of / 4 is desirable. If the amount of alumina is less than this, the purification performance is lowered and sintering of the noble metal is liable to occur. If the amount of titania is less than this, the sulfur poisoning resistance is reduced.
【００２１】なお触媒担持層には、Al2O3-TiO2担体粉末
に加えてアルミナ、シリカ、チタニア、ジルコニアなど
他の酸化物粉末を含んでもよいが、Al2O3-TiO2担体粉末
のみから触媒担持層を構成することが望ましい。またCe
O2粉末を含むことも好ましい。CeO2の酸素吸蔵放出能に
より、浄化性能が一層向上する。またZrO2で安定化され
たCeO2（CeO2−ZrO2複合酸化物）を用いれば、その耐久
性が一層向上する。[0021] Note that the catalyst supporting layer, alumina in addition to Al 2 O 3 -TiO 2 support powder, silica, titania, or but also include other oxide powders such as zirconia, Al 2 O 3 -TiO 2 support powder It is desirable to form the catalyst supporting layer only from the catalyst supporting layer. Also Ce
It is also preferred to include O 2 powder. Purification performance is further improved by the oxygen storage / release capability of CeO 2 . If CeO 2 stabilized with ZrO 2 (CeO 2 -ZrO 2 composite oxide) is used, the durability is further improved.
【００２２】触媒担持層に担持される貴金属としては、
Pt，Rh，Pd，IrあるいはRuの１種又は複数種を用いるこ
とができる。またNOx 吸蔵材としては、アルカリ金属、
アルカリ土類金属及び希土類元素から選ばれる少なくと
も一種を用いることができる。中でもアルカリ度が高く
NOx 吸蔵能の高いアルカリ金属及びアルカリ土類金属の
少なくとも一方を用いるのが好ましい。The noble metals supported on the catalyst supporting layer include:
One or more of Pt, Rh, Pd, Ir or Ru can be used. Examples of the NO x storage material, an alkali metal,
At least one selected from alkaline earth metals and rare earth elements can be used. Above all, alkalinity is high
Preferably used at least one of the NO x storage capacity high alkali metals and alkaline earth metals.
【００２３】アルカリ金属としては、Li、Na、Ｋ、Csが
例示される。アルカリ土類金属とは周期表2A族元素をい
い、Ba、Be、Mg、Ca、Srなどが例示される。また希土類
元素としては、Sc、Ｙ、La、Ce、Pr、Nd、Dy、Ybなどが
例示される。Examples of the alkali metal include Li, Na, K and Cs. The alkaline earth metal refers to an element in Group 2A of the periodic table, and examples include Ba, Be, Mg, Ca, and Sr. Examples of the rare earth element include Sc, Y, La, Ce, Pr, Nd, Dy, and Yb.
【００２４】触媒担持層における貴金属の担持量は、担
体基材１リットルあたりに、Pt及びPdの場合は 0.1〜10
ｇが好ましく、 0.5〜10ｇが特に好ましい。またRhの場
合は0.01〜10ｇが好ましく、0.05〜５ｇが特に好まし
い。またNOx 吸蔵材の担持量は、担体基材１リットルあ
たりに0.05〜 1.0モルの範囲が望ましい。NOx 吸蔵材の
担持量が0.05モル／Ｌより少ないとNOx 吸蔵能が低下
し、 1.0モル／Ｌより多くなると貴金属のシンタリング
を助長することになる。The amount of the noble metal supported on the catalyst supporting layer is 0.1 to 10 for Pt and Pd per liter of the support substrate.
g is preferable, and 0.5 to 10 g is particularly preferable. In the case of Rh, 0.01 to 10 g is preferable, and 0.05 to 5 g is particularly preferable. The loading amount of the NO x storage material, is preferably in the range of 0.05 to 1.0 mol per liter of the carrier base. Loading amount of the NO x storage material is lowered is small and the NO x storage capacity from 0.05 mol / L, will promote more becomes the noble metal sintering of from 1.0 mol / L.
【００２５】触媒担持層は、担体基材１リットルあたり
150〜 500ｇの範囲で形成することが好ましい。触媒担
持層の形成量がこれより少ないと浄化性能が低下し、こ
れより多く形成しても効果が飽和する。The catalyst supporting layer is formed per liter of the carrier substrate.
It is preferable to form in the range of 150 to 500 g. If the formation amount of the catalyst supporting layer is smaller than this, the purification performance is reduced, and if the formation amount is larger than this, the effect is saturated.
【００２６】本発明の排ガス浄化用触媒を製造できる本
発明の製造方法では、先ずアルミナ粒子の表面を粒子径
が10nm以下のそれぞれ独立したチタニア微粒子で被覆し
てなるAl2O3-TiO2担体粉末が製造される。このAl2O3-Ti
O2担体粉末を製造するには、先ず第１工程において、ア
ルミナ粒子と粒子径が10nm以下のチタニアゾルとからな
るスラリーのpHが５未満とされる。次いで第２工程にお
いて、pHが５未満とされたスラリーのpHを５〜８とす
る。これによりチタニアゾルは、凝集することなく高分
散状態でアルミナ粒子表面に被覆される。According to the production method of the present invention capable of producing the exhaust gas purifying catalyst of the present invention, first, an Al 2 O 3 —TiO 2 carrier obtained by coating the surface of alumina particles with independent titania fine particles having a particle diameter of 10 nm or less. A powder is produced. This Al 2 O 3 -Ti
In order to produce the O 2 carrier powder, first, in a first step, the pH of a slurry composed of alumina particles and a titania sol having a particle diameter of 10 nm or less is set to less than 5. Next, in the second step, the pH of the slurry having a pH of less than 5 is adjusted to 5 to 8. Thus, the titania sol is coated on the surface of the alumina particles in a highly dispersed state without aggregation.
【００２７】この機構は以下のように説明される。図10
にアルミナとチタニアのpHとゼータ電位との関係を示
す。図10より、pHが５未満ではアルミナ表面もチタニア
表面もプラスに帯電しており、pHが約５〜８の範囲では
アルミナ表面はプラスに、チタニア表面はマイナスに帯
電していることがわかる。This mechanism is described as follows. FIG.
Fig. 2 shows the relationship between the pH of alumina and titania and the zeta potential. From FIG. 10, it can be seen that when the pH is less than 5, both the alumina surface and the titania surface are positively charged, and when the pH is in the range of about 5 to 8, the alumina surface is positively charged and the titania surface is negatively charged.
【００２８】つまり第１工程においては、pHを５未満と
することにより、アルミナとチタニアのゼータ電位が共
にプラス側であるため、チタニアゾルどうし、アルミナ
粒子どうし及びチタニアゾルとアルミナ粒子は互いに電
気的に反撥した状態となって、スラリー中に高分散した
状態となる。そして第２工程においてpHが５〜８とされ
ると、チタニアゾル表面には負電荷が形成され、アルミ
ナ粒子表面には正電荷が形成される。その結果、チタニ
アゾルどうしは互いに反撥して凝集が抑制され、その一
方アルミナ粒子とチタニアゾルは引き合うため、チタニ
アゾルは独立した状態でアルミナ粒子の表面に付着す
る。これにより、アルミナ粒子表面に粒子径が10nm以下
のそれぞれ独立したチタニアゾルが被覆した粉末が分散
したスラリーが得られる。そしてこのスラリーを濾過・
乾燥することで、アルミナ粒子表面に粒子径が10nm以下
のそれぞれ独立したチタニア微粒子が被覆したAl2O3-Ti
O2担体粉末を製造することができる。That is, in the first step, since the zeta potential of alumina and titania are both positive by setting the pH to less than 5, the titania sol, the alumina particles, and the titania sol and the alumina particles electrically repel each other. And a state of being highly dispersed in the slurry. When the pH is adjusted to 5 to 8 in the second step, a negative charge is formed on the titania sol surface, and a positive charge is formed on the alumina particle surface. As a result, the titania sols repel each other to suppress aggregation. On the other hand, the alumina particles and the titania sol attract each other, so that the titania sol adheres to the surface of the alumina particles in an independent state. As a result, a slurry is obtained in which a powder in which the surface of the alumina particles is coated with independent titania sol having a particle diameter of 10 nm or less is dispersed. And filter this slurry
By drying, Al 2 O 3 -Ti coated on the alumina particle surface with independent titania fine particles having a particle diameter of 10 nm or less
O 2 carrier powder can be produced.
【００２９】第１工程においてpHを５未満とするには、
各種酸物質の添加により行うことができる。排ガス浄化
用触媒としたときに残留しない酸物質が望ましいので、
硝酸を用いることが好ましい。硝酸イオンが残留して
も、排ガスがストイキ〜燃料過剰雰囲気となったときに
還元されてN2となって除去されるため不具合はない。To make the pH less than 5 in the first step,
It can be carried out by adding various acid substances. Since acid substances that do not remain when used as exhaust gas purifying catalysts are desirable,
Preferably, nitric acid is used. Even nitrate ions remain, no problem because it is removed becomes a reduced N 2 when the exhaust gas becomes stoichiometric-fuel-rich atmosphere.
【００３０】また第２工程においてpHを５〜８とするに
も、各種アルカリ物質の添加により行うことができる
が、上記と同様に残留を避ける意味からアンモニアを用
いることが望ましい。In the second step, the pH can be adjusted to 5 to 8 by adding various alkali substances. However, it is preferable to use ammonia in the same manner as described above from the viewpoint of avoiding remaining.
【００３１】第１工程及び第２工程は、スラリーをよく
撹拌しながら行うことが好ましく、超音波振動を利用し
てスラリーを撹拌しながら行うことが望ましい。これに
よりチタニアゾルの凝集を確実に防止することができ、
チタニア微粒子をそれぞれ独立した状態でアルミナ粒子
に被覆することができる。なおプロペラ撹拌などの機械
的撹拌を用いる場合には、機械的撹拌後に超音波振動に
よる撹拌を行うことが望ましい。The first step and the second step are preferably performed while stirring the slurry well, and more preferably, while stirring the slurry using ultrasonic vibration. This makes it possible to reliably prevent aggregation of the titania sol,
The titania fine particles can be individually coated on the alumina particles. When mechanical stirring such as propeller stirring is used, it is desirable to perform stirring by ultrasonic vibration after the mechanical stirring.
【００３２】また第１工程において、先ずアルミナ粒子
のみをスラリー化してpHを５未満に調整しておき、そこ
へチタニアゾルを加えることが望ましい。スラリーのpH
が５を超えた状態でアルミナ粒子とチタニアゾルとが共
存すると、チタニアゾルがアルミナの塩基点に一斉に引
き付けられるため、チタニアゾルが凝集するようにな
る。Further, in the first step, it is desirable that the alumina particles alone are first slurried to adjust the pH to less than 5, and the titania sol is added thereto. Slurry pH
When alumina particles and titania sol coexist in a state in which the value exceeds 5, the titania sol is simultaneously attracted to the base points of alumina, so that the titania sol aggregates.
【００３３】第３工程は、得られたAl2O3-TiO2担体粉末
にNOx 吸蔵材と貴金属を担持する工程である。この工程
は、吸着担持法、蒸発乾固法など従来と同様の担持法を
用いて行うことができる。なお排ガス浄化用触媒は、一
般に触媒担持層をもつハニカム形状あるいはペレット形
状として用いられるが、Al2O3-TiO2担体粉末を含む担体
粉末にNOx 吸蔵材と貴金属の少なくとも一方を担持させ
てから触媒担持層を形成してもよいし、予めAl2O3-TiO2
担体粉末を含む担体粉末から触媒担持層を形成してから
NOx 吸蔵材と貴金属の少なくとも一方を担持することも
できる。The third step is a step of supporting the obtained Al 2 O 3 —TiO 2 carrier powder with a NO x occluding material and a noble metal. This step can be carried out using a conventional supporting method such as an adsorption supporting method and an evaporation to dryness method. Note the exhaust gas-purifying catalyst, generally but used as a honeycomb shape or a pellet shape having a catalyst carrying layer, is supported at least one of the NO x storage material and the noble metal in the support powder containing Al 2 O 3 -TiO 2 support powder The catalyst supporting layer may be formed from Al 2 O 3 -TiO 2
After forming the catalyst support layer from the carrier powder including the carrier powder
At least one of the NO x storage material and the noble metal can be supported.
【００３４】そして本発明の排ガス浄化方法では、上記
した本発明の排ガス浄化用触媒を用い、空燃比（Ａ／
Ｆ）が18以上で燃焼された酸素過剰雰囲気の排ガスと接
触させて排ガス中に含まれるNOx をNOx 吸蔵材に吸蔵
し、空燃比を定期的にストイキ〜燃料過剰に変動させて
NOx 吸蔵材から放出されたNOx を還元浄化する。酸素過
剰雰囲気では、排ガス中に含まれるNOが触媒上で酸化さ
れてNOx となり、それがNO x 吸蔵材に吸蔵される。そし
て定期的にストイキ〜燃料過剰雰囲気とされると、NOx
吸蔵材からNOx が放出され、それが触媒上で排ガス中の
HCやCOと反応して還元される。In the exhaust gas purifying method of the present invention,
The air-fuel ratio (A /
F) is in contact with exhaust gas in an oxygen-excess atmosphere,
NO contained in exhaust gas by touchxNOxOccluded in occlusion material
And periodically vary the air-fuel ratio from stoichiometric to excess fuel.
NOxNO released from the storage materialxTo purify. Excess oxygen
In the excess atmosphere, NO contained in the exhaust gas is oxidized on the catalyst.
NOxAnd it is NO xIt is stored in the storage material. Soshi
If the atmosphere is regularly stoichiometric or fuel-rich, NOx
NO from occlusion materialxIs released on the catalyst
It is reduced by reacting with HC and CO.
【００３５】そして触媒担持層においては、アルミナ粒
子をチタニア微粒子が被覆しているためアルミナにSOx
が吸着しにくく、NOx 吸蔵材とSOx との反応が抑制され
る。またチタニアとNOx 吸蔵材との界面が増加するこ
と、これにより分解し易い複合酸化物前駆体が形成され
ること、などの理由により吸着したSOx の脱離が容易と
なると考えられ、高温耐久後にも硫黄被毒を十分に抑制
することができ、NOx 浄化能の低下を十分に抑制するこ
とができる。In the catalyst supporting layer, since alumina particles are covered with titania fine particles, SO x is added to alumina.
Are not easily adsorbed, and the reaction between the NO x storage material and SO x is suppressed. Also, it is considered that the desorption of the adsorbed SO x becomes easy due to an increase in the interface between titania and the NO x storage material, thereby forming a decomposable composite oxide precursor, and the like. Even after durability, sulfur poisoning can be sufficiently suppressed, and a decrease in NO x purification ability can be sufficiently suppressed.
【００３６】[0036]
【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。The present invention will be specifically described below with reference to examples and comparative examples.
【００３７】（実施例１）硝酸でpH２に調整したイオン
交換水 500ccに、プロペラ撹拌器を用いて撹拌しなが
ら、粒子径 200〜 500nmのγ-Al2O3粉末25ｇと、チタニ
アゾル（粒子径７nm、pH 1.5、固形分30重量％）83.3ｇ
を２リットルガラスビーカー中で混合した。さらに硝酸
を添加してpH２に調整し、次いでビーカーを超音波洗浄
機に入れて20分間超音波処理を行った。Example 1 25 g of γ-Al 2 O 3 powder having a particle size of 200 to 500 nm and titania sol (particle size) were stirred in 500 cc of ion-exchanged water adjusted to pH 2 with nitric acid using a propeller stirrer while stirring. 7nm, pH 1.5, solid content 30% by weight) 83.3g
Was mixed in a 2 liter glass beaker. Further, the pH was adjusted to 2 by adding nitric acid, and then the beaker was placed in an ultrasonic cleaner and subjected to ultrasonic treatment for 20 minutes.
【００３８】次にプロペラ撹拌器を用いて上記スラリー
を撹拌しながら、スラリー中にアンモニア水を徐々に滴
下してpH７とした。その後濾過し、80℃で乾燥後、大気
中にて 300℃で５時間焼成してAl2O3-TiO2担体粉末を得
た。このAl2O3-TiO2担体粉末の電子顕微鏡写真を図１及
び図２に、またAl2O3-TiO2担体粉末の模式図を図３に示
す。Next, while stirring the slurry using a propeller stirrer, ammonia water was gradually dropped into the slurry to adjust the pH to 7. Thereafter, the mixture was filtered, dried at 80 ° C., and calcined in the air at 300 ° C. for 5 hours to obtain an Al 2 O 3 —TiO 2 carrier powder. The electron micrograph of the Al 2 O 3 -TiO 2 support powder in Figures 1 and 2, also shows a schematic diagram of the Al 2 O 3 -TiO 2 support powder in FIG.
【００３９】図１及び図２より、アルミナ粒子の表面の
ほぼ全面をチタニア微粒子が被覆している様子が観察さ
れ、Al2O3-TiO2担体粉末の粒子は図３のような構造と考
えられる。なおチタニアは、アナターゼ型となってい
る。From FIGS. 1 and 2, it is observed that titania particles cover almost the entire surface of the alumina particles, and the particles of the Al 2 O 3 —TiO 2 carrier powder are considered to have a structure as shown in FIG. Can be Note that titania is of an anatase type.
【００４０】得られたAl2O3-TiO2担体粉末の所定量に、
所定濃度のジニトロジアンミン白金錯体水溶液の所定量
を含浸し、蒸発乾固してAl2O3-TiO2担体粉末 120ｇあた
り２ｇのPtを担持した。次いで所定濃度の硝酸ロジウム
水溶液の所定量を含浸し、蒸発乾固してAl2O3-TiO2担体
粉末 120ｇあたり 0.1ｇのRhを担持した。これを大気中
にて 250℃で３時間焼成した。A predetermined amount of the obtained Al 2 O 3 —TiO 2 carrier powder was
A predetermined amount of an aqueous solution of a dinitrodiammine platinum complex having a predetermined concentration was impregnated and evaporated to dryness to carry 2 g of Pt per 120 g of Al 2 O 3 —TiO 2 carrier powder. Next, a predetermined amount of an aqueous solution of rhodium nitrate having a predetermined concentration was impregnated and evaporated to dryness to carry 0.1 g of Rh per 120 g of Al 2 O 3 —TiO 2 carrier powder. This was fired in the air at 250 ° C. for 3 hours.
【００４１】次にPtとRhを担持したAl2O3-TiO2担体粉末
の所定量に、所定濃度の酢酸バリウム水溶液の所定量を
含浸し、蒸発乾固後 500℃で３時間焼成して、Al2O3-Ti
O2担体粉末 120ｇあたり 0.2モルのBaを担持した。Next, a predetermined amount of an Al 2 O 3 —TiO 2 carrier powder supporting Pt and Rh is impregnated with a predetermined amount of a barium acetate aqueous solution having a predetermined concentration, and evaporated to dryness, and then calcined at 500 ° C. for 3 hours. , Al 2 O 3 -Ti
0.2 mol of Ba was supported per 120 g of the O 2 carrier powder.
【００４２】得られた触媒粉末を用い、定法により粒子
径が 300〜 700μｍのペレット形状に成形してペレット
触媒を調製した。Using the obtained catalyst powder, a pellet catalyst was prepared by a conventional method into a pellet having a particle diameter of 300 to 700 μm.
【００４３】（比較例１）イオン交換水 500ccに、プロ
ペラ撹拌器を用いて撹拌しながら、粒子径 200〜500nm
のγ-Al2O3粉末25ｇと、チタニアゾル（粒子径７nm、pH
1.5、固形分30重量％）83.3ｇを２リットルガラスビー
カー中で混合した。プロペラ撹拌器で20分間撹拌した後
濾過し、80℃で乾燥後、大気中にて 300℃で５時間焼成
してAl2O3-TiO2担体粉末を得た。Comparative Example 1 A particle diameter of 200 to 500 nm was stirred in 500 cc of ion-exchanged water using a propeller stirrer.
25 g of γ-Al 2 O 3 powder and titania sol (particle diameter 7 nm, pH
83.3 g was mixed in a 2 liter glass beaker. After stirring for 20 minutes with a propeller stirrer, the mixture was filtered, dried at 80 ° C., and calcined at 300 ° C. for 5 hours in the atmosphere to obtain an Al 2 O 3 —TiO 2 carrier powder.
【００４４】このAl2O3-TiO2担体粉末を用い、実施例１
と同様にして比較例１のペレット触媒を調製した。Example 1 using this Al 2 O 3 —TiO 2 carrier powder
In the same manner as in Example 1, a pellet catalyst of Comparative Example 1 was prepared.
【００４５】（比較例２）平均粒子径が20nmの微粒子チ
タニア粉末と、実施例１で用いたγ-Al2O3粉末を重量比
で１対１となるように混合し、ボールミルにて24時間ミ
リングして十分に混合した。このAl2O3-TiO2担体粉末の
電子顕微鏡写真を図４に、またこのAl2O3-TiO2担体粉末
の模式図を図５に示す。Comparative Example 2 The fine titania powder having an average particle diameter of 20 nm and the γ-Al 2 O 3 powder used in Example 1 were mixed at a weight ratio of 1: 1. Milled for hours and mixed well. The electron micrograph of the Al 2 O 3 -TiO 2 support powder 4, also shows a schematic diagram of the Al 2 O 3 -TiO 2 support powder in FIG.
【００４６】図４より、凝集したチタニア粒子がアルミ
ナ粒子表面に付着している様子が観察され、このAl2O3-
TiO2担体粉末は図５のような構成であると考えられる。[0046] From FIG. 4, how the aggregated titania particles are attached to the alumina particle surface is observed, the Al 2 O 3 -
It is considered that the TiO 2 carrier powder has a configuration as shown in FIG.
【００４７】このAl2O3-TiO2担体粉末を用い、実施例１
と同様にして比較例２のペレット触媒を調製した。Example 1 using this Al 2 O 3 —TiO 2 carrier powder
In the same manner as in the above, a pellet catalyst of Comparative Example 2 was prepared.
【００４８】＜試験・評価＞実施例１及び比較例１〜２
のペレット触媒をそれぞれ１ｇ採取し、それぞれ内径10
mmの石英管にプラグ状に充填した。これに、表１に示す
ようにSO2 を含む酸素過剰雰囲気（リーン）と燃料過剰
雰囲気（リッチ）のモデルガスを、30秒間隔で切り替え
てそれぞれ流速 500ml／分で流通させる耐久試験を行っ
た。なお触媒床温度を図６に示すパターンで変化させ、
モデルガス中のSO2 はステップ１とステップ２の間のみ
含ませた。<Test / Evaluation> Example 1 and Comparative Examples 1-2
1 g of each pellet catalyst was collected,
The plug was filled into a mm quartz tube. As shown in Table 1, a durability test was conducted in which model gases in an oxygen-excess atmosphere (lean) and a fuel-excess atmosphere (rich) containing SO 2 were switched at intervals of 30 seconds and flowed at a flow rate of 500 ml / min. . The catalyst bed temperature was changed in the pattern shown in FIG.
SO 2 in the model gas was included only between Step 1 and Step 2.
【００４９】[0049]
【表１】 [Table 1]
【００５０】上記した耐久試験後の各触媒を、１％のH2
を含む窒素ガス中にて 100℃から 800℃まで20℃／分の
昇温速度で加熱したときに、質量分析計で測定した硫黄
の脱離挙動を図７に示す。図７より、実施例１の触媒は
比較例１〜２の触媒に比べて低温から硫黄が脱離し始
め、脱離量も多いことがわかる。After the above-mentioned endurance test, each catalyst was replaced with 1% H 2
FIG. 7 shows the desorption behavior of sulfur measured by a mass spectrometer when heated at a heating rate of 20 ° C./min from 100 ° C. to 800 ° C. in a nitrogen gas containing. FIG. 7 shows that the catalyst of Example 1 began to desorb sulfur at a lower temperature than the catalysts of Comparative Examples 1 and 2, and the amount of desorption was large.
【００５１】次に、耐久試験後の各ペレット触媒をそれ
ぞれ 0.5ｇ採取し、内径10mmの石英管にプラグ状にそれ
ぞれ充填した。前処理は行わないで、 200〜 400℃の範
囲で50℃毎に飽和NOx 吸蔵量とリッチスパイクNOx 吸蔵
量をそれぞれ測定した。それぞれの結果を図８及び図９
に示す。Next, 0.5 g of each pellet catalyst after the endurance test was sampled and filled into a quartz tube having an inner diameter of 10 mm in a plug shape. Without the pretreatment, the saturated NO x storage amount and the rich spike NO x storage amount were measured at every 50 ° C. in the range of 200 to 400 ° C. 8 and 9 show the results.
Shown in
【００５２】測定には表２に示すモデルガスを用い、ガ
ス流速は３Ｌ／分とした。そして各温度においてリッチ
ガスを流通させ、触媒上に吸蔵されているNOx が無い状
態を作る。次にリーンガスを供給し、10分間に触媒に吸
蔵されたNOx 量を測定して飽和NOx 吸蔵量とした。その
後リッチガスを３秒間供給し、再びリーンガスを供給す
る。このリーンガス供給開始から５分間に吸蔵されたNO
x 量を測定し、リッチスパイクNOx 吸蔵量とした。For the measurement, model gases shown in Table 2 were used, and the gas flow rate was 3 L / min. And allowed to flow rich gas at each temperature, making NO x is no state of being occluded in the catalyst. Then supplying the lean gas, by measuring the amount of NO x occluded in the catalyst was saturated the NO x storage amount in 10 min. Thereafter, rich gas is supplied for 3 seconds, and lean gas is supplied again. NO stored for 5 minutes from the start of this lean gas supply
The x amount was measured and defined as a rich spike NO x storage amount.
【００５３】[0053]
【表２】 [Table 2]
【００５４】図８及び図９より、実施例１の触媒は各比
較例の触媒に比べてNOx 吸蔵量が多く、耐久後のNOx 吸
蔵能に優れていることがわかる。これは、アルミナ粒子
の表面のほぼ全面をそれぞれ独立したチタニア微粒子が
被覆しているAl2O3-TiO2担体粉末を用いた効果であるこ
とが明らかである。[0054] 8 and 9, the catalyst of Example 1 is often the NO x storage amount in comparison with the catalysts of Comparative Examples are excellent in the NO x storage ability after endurance. This is apparently due to the effect of using the Al 2 O 3 —TiO 2 carrier powder in which almost all the surfaces of the alumina particles are coated with independent titania fine particles.
【００５５】[0055]
【発明の効果】すなわち本発明の排ガス浄化用触媒及び
排ガス浄化方法によれば、硫黄被毒を効果的に抑制する
ことができ、高温耐久後のNOx 浄化能がさらに向上す
る。Effects of the Invention] That is, according to the catalyst and the exhaust gas purifying method for purifying an exhaust gas of the present invention, it is possible to effectively suppress the sulfur poisoning, further improves the NO x purification performance after the high-temperature durability.
【図１】本発明の一実施例の排ガス浄化用触媒に用いた
担体の粒子構造を示す電子顕微鏡写真である。FIG. 1 is an electron micrograph showing the particle structure of a carrier used in an exhaust gas purifying catalyst according to one embodiment of the present invention.
【図２】本発明の一実施例の排ガス浄化用触媒に用いた
担体の粒子構造を示す電子顕微鏡写真である。FIG. 2 is an electron micrograph showing the particle structure of a carrier used in an exhaust gas purifying catalyst according to one embodiment of the present invention.
【図３】本発明の一実施例の排ガス浄化用触媒に用いた
担体の粒子構造を示す模式的説明図である。FIG. 3 is a schematic explanatory view showing a particle structure of a carrier used in an exhaust gas purifying catalyst according to one embodiment of the present invention.
【図４】本発明の比較例２の排ガス浄化用触媒に用いた
担体の粒子構造を示す電子顕微鏡写真である。FIG. 4 is an electron micrograph showing the particle structure of a carrier used for an exhaust gas purifying catalyst of Comparative Example 2 of the present invention.
【図５】本発明の比較例２の排ガス浄化用触媒に用いた
担体の粒子構造を示す模式的説明図である。FIG. 5 is a schematic explanatory view showing a particle structure of a carrier used for an exhaust gas purifying catalyst of Comparative Example 2 of the present invention.
【図６】実施例及び比較例における耐久試験の温度パタ
ーンを示すグラフである。FIG. 6 is a graph showing a temperature pattern of an endurance test in Examples and Comparative Examples.
【図７】実施例及び比較例の触媒の硫黄脱離量と温度と
の関係を示すグラフである。FIG. 7 is a graph showing the relationship between the sulfur desorption amount and the temperature of the catalysts of Examples and Comparative Examples.
【図８】実施例及び比較例の触媒の飽和NOx 吸蔵量と温
度との関係を示すグラフである。FIG. 8 is a graph showing the relationship between the saturated NO x storage amount and the temperature of the catalysts of Examples and Comparative Examples.
【図９】実施例及び比較例の触媒のリッチスパイクNOx
吸蔵量と温度との関係を示すグラフである。FIG. 9 shows rich spike NO x of the catalysts of Examples and Comparative Examples.
It is a graph which shows the relationship between the amount of occlusion and temperature.
【図10】アルミナとチタニアのゼータ電位とpHとの関係
を示すグラフである。FIG. 10 is a graph showing the relationship between the zeta potential of alumina and titania and pH.
─────────────────────────────────────────────────────
────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成１１年７月１４日（１９９９．７．１
４）[Submission date] July 14, 1999 (1999.7.1)
4)
【手続補正１】[Procedure amendment 1]
【補正対象書類名】図面[Document name to be amended] Drawing
【補正対象項目名】図１[Correction target item name] Fig. 1
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【図１】 FIG.
【手続補正２】[Procedure amendment 2]
【補正対象書類名】図面[Document name to be amended] Drawing
【補正対象項目名】図２[Correction target item name] Figure 2
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【図２】 FIG. 2
【手続補正３】[Procedure amendment 3]
【補正対象書類名】図面[Document name to be amended] Drawing
【補正対象項目名】図４[Correction target item name] Fig. 4
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【図４】 FIG. 4
───────────────────────────────────────────────────── 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） Ｆ０１Ｎ 3/08 Ｆ０１Ｎ 3/28 ３０１Ｃ 3/28 ３０１ ３０１Ｐ Ｂ０１Ｄ 53/36 １０２Ｂ (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 (72)発明者 長谷川 世里子 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 AA12 AB06 BA11 BA14 BA39 FB10 FB11 FB12 GA01 GA06 GB01X GB02W GB03W GB04W GB05W GB06W GB07W GB10X GB16X GB17X 4D048 AA06 AB02 BA01Y BA02Y BA03X BA07X BA13Y BA14Y BA15X BA30X BA33X BA41X BA42X BB01 4G069 AA01 AA03 AA04 AA08 AA09 BA01A BA01B BA01C BA04A BA04B BA04C BB04A BB04B BB04C BB06A BB06B BB06C BC01A BC08A BC08B BC08C BC13B BC13C BC69A BC69B BC69C BC71A BC71B BC71C BC75A BC75B BC75C BD02A BD02B BD02C CA03 CA08 CA13 DA06 EA02Y EB18X EB18Y EB19 EC14X EC17Y ED07 FB14 FB15 ──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. 7 Identification symbol FI Theme coat ゛ (Reference) F01N 3/08 F01N 3/28 301C 3/28 301 301P B01D 53/36 102B (72) Inventor Akihiko Suda Aichi 41 Toyota Chuo R & D Co., Ltd., No. 41, Nagachute-cho, Nagakute-machi, Aichi-gun, Japan. Terms (reference) 3G091 AA02 AA12 AB06 BA11 BA14 BA39 FB10 FB11 FB12 GA01 GA06 GB01X GB02W GB03W GB04W GB05W GB06W GB07W GB10X GB16X GB17X 4D048 AA06 AB02 BA01Y BA02Y BA03X BA07X BA13A BAA ABAAA BAXAA BAXA BA04A BA04B BA04C BB04A BB04B BB04C BB06A BB06B BB06C BC01A BC08A BC08B BC08C BC13B BC1 3C BC69A BC69B BC69C BC71A BC71B BC71C BC75A BC75B BC75C BD02A BD02B BD02C CA03 CA08 CA13 DA06 EA02Y EB18X EB18Y EB19 EC14X EC17Y ED07 FB14 FB15
Claims (4)
多孔質酸化物よりなる触媒担持層と、該触媒担持層に担
持された貴金属と、該触媒担持層に担持されたアルカリ
金属，アルカリ土類金属及び希土類元素から選ばれる少
なくとも一種のNOx 吸蔵材と、からなるNOx 吸蔵還元型
の排ガス浄化用触媒において、 該触媒担持層には、アルミナ粒子の表面を粒子径が10nm
以下のそれぞれ独立したチタニア微粒子で被覆してなる
Al2O3-TiO2担体粉末を含むことを特徴とする排ガス浄化
用触媒。1. A carrier substrate, a catalyst supporting layer made of a porous oxide formed on the carrier substrate, a noble metal supported on the catalyst supporting layer, and an alkali supported on the catalyst supporting layer. metal, and at least one NO x storage material selected from alkaline earth metals and rare earth elements, in the NO x storage-reduction type exhaust gas purifying catalyst comprising, in the catalyst supporting layer, the particle diameter of the surface of the alumina particles 10nm
Coated with the following independent titania fine particles
An exhaust gas purifying catalyst comprising an Al 2 O 3 —TiO 2 carrier powder.
ニアゾルとからなるスラリーのpHを５未満とする第１工
程と、 pHが５未満とされた該スラリーのpHを５〜８とすること
で該アルミナ粒子の表面が粒子径が10nm以下のそれぞれ
独立したチタニア微粒子で被覆されたAl2O3-TiO2担体粉
末を得る第２工程と、 該Al2O3-TiO2担体粉末にアルカリ金属，アルカリ土類金
属及び希土類元素から選ばれる少なくとも一種のNOx 吸
蔵材と貴金属とを担持する第３工程と、よりなることを
特徴とする排ガス浄化用触媒の製造方法。2. A first step in which the pH of a slurry comprising alumina particles and a titania sol having a particle diameter of 10 nm or less is less than 5, and a step in which the pH of the slurry whose pH is less than 5 is 5 to 8 A second step of obtaining an Al 2 O 3 -TiO 2 carrier powder in which the surface of the alumina particles is coated with independent titania fine particles having a particle diameter of 10 nm or less, and adding an alkali metal to the Al 2 O 3 -TiO 2 carrier powder. , third step and, method of manufacturing the exhaust gas purifying catalyst characterized by comprising more bearing and at least one NO x storage material and a noble metal selected from alkaline earth metals and rare earth elements.
波振動により前記スラリーを撹拌しながら行うことを特
徴とする請求項２に記載の排ガス浄化用触媒の製造方
法。3. The method for producing an exhaust gas purifying catalyst according to claim 2, wherein the first step and the second step are performed while stirring the slurry by ultrasonic vibration.
空燃比（Ａ／Ｆ）が18以上で燃焼された酸素過剰雰囲気
の排ガスと接触させて該排ガス中に含まれるNOx を該NO
x 吸蔵材に吸蔵し、空燃比を定期的にストイキ〜燃料過
剰に変動させて該NOx 吸蔵材から放出されたNOx を還元
浄化することを特徴とする排ガス浄化方法。4. The exhaust gas purifying catalyst according to claim 1,
Air-fuel ratio (A / F) said the NO x contained in the exhaust gas is contacted with the exhaust gas of which oxygen-rich atmosphere combustion with 18 or more NO
exhaust gas purification method, characterized in that occluded x storage material, regularly stoichiometric-fuel excessively varying the air-fuel ratio to reduce and purify the released NO x from the the NO x storage material.
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|---|---|---|---|
| JP18315599A JP4240250B2 (en) | 1999-06-29 | 1999-06-29 | Exhaust gas purification catalyst, method for producing the same, and exhaust gas purification method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18315599A JP4240250B2 (en) | 1999-06-29 | 1999-06-29 | Exhaust gas purification catalyst, method for producing the same, and exhaust gas purification method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2001009279A true JP2001009279A (en) | 2001-01-16 |
| JP4240250B2 JP4240250B2 (en) | 2009-03-18 |
Family
ID=16130772
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|---|---|---|---|
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| Country | Link |
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| JP2006297234A (en) * | 2005-04-18 | 2006-11-02 | Toyota Motor Corp | Method of manufacturing composite material |
| US7220702B2 (en) | 2001-02-19 | 2007-05-22 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas purification catalyst |
| JP2008200603A (en) * | 2007-02-20 | 2008-09-04 | Denso Corp | Catalyst material manufacturing method and catalyst material manufactured by the same |
| WO2009001962A1 (en) | 2007-06-27 | 2008-12-31 | Toyota Jidosha Kabushiki Kaisha | Process for producing catalyst support for exhaust gas purification and catalyst support for exhaust gas purification |
| JP2011513055A (en) * | 2008-03-05 | 2011-04-28 | ロデイア・オペラシヨン | Compositions based on zirconium oxide, titanium oxide, or mixed zirconium titanium oxide on alumina or aluminum oxyhydroxide supports, preparation methods, and use as catalysts |
| US9381496B2 (en) | 2009-03-18 | 2016-07-05 | Toyota Jidosha Kabushiki Kaisha | Nanoparticle carrying method |
| WO2019117382A1 (en) * | 2017-12-14 | 2019-06-20 | 한국생산기술연구원 | Metal structure-based denitrification catalyst, for selective catalytic reduction, using coating slurry and method for preparing same |
| WO2021010892A1 (en) * | 2019-07-15 | 2021-01-21 | National University Of Singapore | A ceramic membrane for water and wastewater treatment |
| CN112584926A (en) * | 2018-08-20 | 2021-03-30 | 乐金华奥斯有限公司 | Catalyst for exhaust gas purification |
-
1999
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| CN112584926A (en) * | 2018-08-20 | 2021-03-30 | 乐金华奥斯有限公司 | Catalyst for exhaust gas purification |
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