JP2002191989A - Catalyst for cleaning exhaust gas and method for manufacturing the same - Google Patents
Catalyst for cleaning exhaust gas and method for manufacturing the sameInfo
- Publication number
- JP2002191989A JP2002191989A JP2001294609A JP2001294609A JP2002191989A JP 2002191989 A JP2002191989 A JP 2002191989A JP 2001294609 A JP2001294609 A JP 2001294609A JP 2001294609 A JP2001294609 A JP 2001294609A JP 2002191989 A JP2002191989 A JP 2002191989A
- Authority
- JP
- Japan
- Prior art keywords
- oxide carrier
- powder
- alkali metal
- specific surface
- surface area
- 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 108
- 238000000034 method Methods 0.000 title claims description 21
- 238000004519 manufacturing process Methods 0.000 title claims description 19
- 238000004140 cleaning Methods 0.000 title abstract 2
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 93
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 83
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 77
- 229910052751 metal Inorganic materials 0.000 claims abstract description 6
- 239000002184 metal Substances 0.000 claims abstract description 6
- 239000000843 powder Substances 0.000 claims description 108
- 239000010410 layer Substances 0.000 claims description 99
- 239000000758 substrate Substances 0.000 claims description 58
- 239000007789 gas Substances 0.000 claims description 41
- 239000011248 coating agent Substances 0.000 claims description 22
- 238000000576 coating method Methods 0.000 claims description 22
- 239000002245 particle Substances 0.000 claims description 21
- -1 alkali metal hydrogen tartrate Chemical class 0.000 claims description 17
- 239000011247 coating layer Substances 0.000 claims description 11
- 238000010304 firing Methods 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- 239000011812 mixed powder Substances 0.000 claims description 8
- 238000001354 calcination Methods 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 4
- 238000000354 decomposition reaction Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 2
- 239000003513 alkali Substances 0.000 claims 2
- 150000002739 metals Chemical class 0.000 abstract 1
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 75
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 35
- 230000000052 comparative effect Effects 0.000 description 34
- 238000003860 storage Methods 0.000 description 29
- 229920006395 saturated elastomer Polymers 0.000 description 24
- 239000002002 slurry Substances 0.000 description 24
- 239000007864 aqueous solution Substances 0.000 description 17
- 229910052697 platinum Inorganic materials 0.000 description 14
- 230000000694 effects Effects 0.000 description 13
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 12
- 238000004453 electron probe microanalysis Methods 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 9
- 238000010586 diagram Methods 0.000 description 9
- 238000009826 distribution Methods 0.000 description 9
- 239000011232 storage material Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- 229910052700 potassium Inorganic materials 0.000 description 7
- 230000009467 reduction Effects 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 238000011156 evaluation Methods 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 235000010333 potassium nitrate Nutrition 0.000 description 6
- 239000004323 potassium nitrate Substances 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 235000016337 monopotassium tartrate Nutrition 0.000 description 5
- KYKNRZGSIGMXFH-ZVGUSBNCSA-M potassium bitartrate Chemical compound [K+].OC(=O)[C@H](O)[C@@H](O)C([O-])=O KYKNRZGSIGMXFH-ZVGUSBNCSA-M 0.000 description 5
- 238000000746 purification Methods 0.000 description 5
- FEWJPZIEWOKRBE-UHFFFAOYSA-M 3-carboxy-2,3-dihydroxypropanoate Chemical compound OC(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-M 0.000 description 4
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 4
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- 239000002585 base Substances 0.000 description 4
- 235000002906 tartaric acid Nutrition 0.000 description 4
- 239000011975 tartaric acid Substances 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 238000005470 impregnation Methods 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 150000002736 metal compounds Chemical class 0.000 description 3
- 229940086065 potassium hydrogentartrate Drugs 0.000 description 3
- 239000010970 precious metal Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- FEWJPZIEWOKRBE-JCYAYHJZSA-M L-tartrate(1-) Chemical compound OC(=O)[C@H](O)[C@@H](O)C([O-])=O FEWJPZIEWOKRBE-JCYAYHJZSA-M 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910052878 cordierite Inorganic materials 0.000 description 2
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 229940081543 potassium bitartrate Drugs 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 101000741917 Homo sapiens Serine/threonine-protein phosphatase 1 regulatory subunit 10 Proteins 0.000 description 1
- 102100038743 Serine/threonine-protein phosphatase 1 regulatory subunit 10 Human genes 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000007853 buffer solution Substances 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 229910052730 francium Inorganic materials 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、排ガス浄化用触媒
とその製造方法に関する。[0001] The present invention relates to an exhaust gas purifying catalyst and a method for producing the same.
【０００２】[0002]
【従来の技術】排ガス中のNOx を効率よく浄化できる触
媒として、近年、NOx 吸蔵還元型触媒が利用されてい
る。このNOx 吸蔵還元型触媒は、例えばアルミナなどの
担体にPtなどの貴金属とBa，ＫなどのNOx 吸蔵材を担持
してなるものである。このNOx 吸蔵還元型触媒は、通常
は燃料リーンで運転されパルス状に燃料リッチ（リッチ
スパイク）として運転されるエンジンの排ガス中に配置
され、酸素過剰雰囲気で排ガス中のNOが酸化されてNOx
吸蔵材に吸蔵される。そしてリッチスパイク時にNO x 吸
蔵材に吸蔵されているNOxが放出され、排ガス中の還元
成分によって還元浄化される。これによりNOx 吸蔵材は
NOx 吸蔵能が回復し、再び酸素過剰雰囲気でNOx を吸蔵
する。したがってNOx 吸蔵還元型触媒によれば、リーン
バーンエンジンからの排ガス中のNOx を効率よく浄化す
ることができる。2. Description of the Related Art NO in exhaust gasx That can efficiently purify
In recent years, NOx Storage-reduction catalysts are used
You. This NOx The storage reduction catalyst is, for example, alumina or the like.
Precious metals such as Pt and NO such as Ba and Kx Supports occlusion material
It is made. This NOx Storage reduction catalysts are usually
Is operated in fuel lean and fuel-rich
Placed in the exhaust gas of an engine operated as a spike)
NO in the exhaust gas is oxidized in an oxygen-rich atmospherex
It is stored in the storage material. And NO during rich spike x Sucking
NO stored in the storage materialxIs released and reduced in exhaust gas
It is reduced and purified by the components. This makes NOx Occlusion material
NOx The storage capacity is restored, and NOx Occlude
I do. Therefore NOx According to the storage reduction catalyst, lean
NO in exhaust gas from burn enginex Efficiently purify
Can be
【０００３】自動車の排ガス浄化用触媒としては、ハニ
カム型のモノリス触媒が一般的である。そのためNOx 吸
蔵還元型触媒も同様のハニカム形状として用いられてい
る。このようなNOx 吸蔵還元型触媒を製造する場合、先
ずアルミナなどの担体粉末からバインダーとともにスラ
リーを調製し、コーディエライトなどから形成されたハ
ニカム基材表面にウォッシュコートした後焼成してコー
ト層を形成する。その後、貴金属化合物が溶解した水溶
液を用いて貴金属を担持し、さらにNOx 吸蔵材の塩など
が溶解した水溶液を用いてNOx 吸蔵材を担持している。[0003] A honeycomb type monolith catalyst is generally used as an exhaust gas purifying catalyst for automobiles. Therefore the NO x storage-reduction catalyst is also used as a similar honeycomb-shaped. When producing such a NO x storage-and-reduction type catalyst, is first to prepare a slurry with a binder from the support powder such as alumina, coating layer by baking after wash-coated on the honeycomb substrate surface formed from such cordierite To form Thereafter, using an aqueous solution of noble metal compound is dissolved supporting the noble metal, carries a the NO x storage material with an aqueous solution such as dissolved therein further salts of the NO x storage material.
【０００４】貴金属の担持法には、イオン交換反応を利
用した吸着担持法と、物理的な含浸担持法が知られてい
る。吸着担持法は、担体表面の水酸基と貴金属塩などと
の反応によって、貴金属塩などを担体に吸着させ、その
後焼成して貴金属を担持する方法である。もう一つの含
浸担持法は、貴金属化合物を溶解した水溶液をコート層
に含浸させ、その後水分を蒸発させ焼成して貴金属を担
持する方法である。As a method of supporting a noble metal, an adsorption supporting method utilizing an ion exchange reaction and a physical impregnation supporting method are known. The adsorption-supporting method is a method in which a noble metal salt or the like is adsorbed on a carrier by a reaction between a hydroxyl group on the surface of the carrier and a noble metal salt or the like, and then calcined to support the noble metal. Another impregnation-supporting method is a method in which an aqueous solution in which a noble metal compound is dissolved is impregnated into a coat layer, and then the moisture is evaporated and fired to support the noble metal.
【０００５】またNOx 吸蔵材の担持には、含浸担持法が
一般に用いられている。なお、NOx吸蔵材を担持後に貴
金属を担持すると、一旦担持されたNOx 吸蔵材が貴金属
化合物の水溶液中に溶出し、NOx 吸蔵材の担持分布が不
均一となる。したがって先ず貴金属を担持し、その後NO
x 吸蔵材を担持するのが望ましい。For supporting the NO x occluding material, an impregnation supporting method is generally used. Incidentally, when carrying the precious metal after carrying the NO x storage material, once it supported the NO x storage material is eluted in an aqueous solution of noble metal compound, the supported distribution of the NO x storage material becomes uneven. Therefore, noble metal is supported first, and then NO
It is desirable to carry x storage material.
【０００６】[0006]
【発明が解決しようとする課題】NOx 吸蔵材としてのア
ルカリ金属は、高温域におけるNOx 吸蔵能に優れ、NOx
吸蔵還元型触媒には必須成分とされている。ところが上
記したように貴金属を担持した後にアルカリ金属を含浸
担持すると、担持されている貴金属の表面にまでアルカ
リ金属が担持され、貴金属の活性点が覆われて活性が低
下するという不具合があった。アルカリ金属は融点が比
較的低いため、触媒として使用中に担体上を移動して貴
金属を覆う場合もある。またアルカリ金属と貴金属は相
互作用が大きいためか、互いに近接すると貴金属の粒成
長が生じやすいという不具合もあった。さらにアルカリ
金属と貴金属とが同一担体に近接して担持されている
と、低温域におけるNOの酸化活性が低下して低温域のNO
x 浄化活性が低下するという問題もある。Alkali metal as the NO x storage material [0005] is excellent in the NO x storage ability in a high temperature region, NO x
It is an essential component of the storage reduction catalyst. However, when the alkali metal is impregnated and supported after the noble metal is supported as described above, the alkali metal is supported even on the surface of the noble metal being supported, and the active points of the noble metal are covered and the activity is reduced. Since the alkali metal has a relatively low melting point, it may move on a carrier and cover the noble metal during use as a catalyst. In addition, there is also a problem in that the alkali metal and the noble metal have a large interaction, and when they come close to each other, grain growth of the noble metal is likely to occur. Further, when the alkali metal and the noble metal are supported close to the same carrier, the oxidizing activity of NO in the low-temperature region decreases, and the NO in the low-temperature region is reduced.
x There is also a problem that the purification activity is reduced.
【０００７】そこで貴金属とアルカリ金属とを分離して
担持することが望ましいと考えられている。例えば貴金
属を担持した担体粉末とアルカリ金属を担持した担体粉
末とを混合してコート層を形成する方法が考えられる
が、この方法でもウォッシュコート時にアルカリ金属が
スラリー中に溶出するという不具合がある。Therefore, it is considered that it is desirable to carry the noble metal and the alkali metal separately. For example, a method of forming a coat layer by mixing a carrier powder carrying a noble metal and a carrier powder carrying an alkali metal is conceivable, but this method also has a disadvantage that the alkali metal is eluted into the slurry during wash coating.
【０００８】本発明はこのような事情に鑑みてなされた
ものであり、アルカリ金属と貴金属とを分離担持して相
互作用を防止するとともに、高温耐久時にアルカリ金属
の移動を防止できる排ガス浄化触媒とすることを目的と
する。The present invention has been made in view of such circumstances, and an exhaust gas purifying catalyst which can separate and carry an alkali metal and a noble metal to prevent an interaction and prevent migration of an alkali metal during high-temperature durability. The purpose is to do.
【０００９】[0009]
【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、アルカリ金属を担持し
た第１酸化物担体と、貴金属を担持した第２酸化物担体
とよりなり、第１酸化物担体の比表面積が第２酸化物担
体の比表面積より大きいことにある。第１酸化物担体と
第２酸化物担体の比表面積の差は30m2／ｇ以上であるこ
とが望ましい。The feature of the exhaust gas purifying catalyst of the present invention which solves the above-mentioned problems is that it comprises a first oxide carrier carrying an alkali metal and a second oxide carrier carrying a noble metal, The specific surface area of the first oxide carrier is larger than the specific surface area of the second oxide carrier. It is desirable that the difference between the specific surface areas of the first oxide carrier and the second oxide carrier is 30 m 2 / g or more.
【００１０】またアルカリ金属を担持した第１酸化物担
体を含む下層と貴金属を担持した第２酸化物担体を含む
上層からなる二層構造のコート層がハニカム基材表面に
形成されてなる排ガス浄化用触媒とすることもできる
が、アルカリ金属を担持した第１酸化物担体粉末と、貴
金属を担持した第２酸化物担体粉末とが混在したコート
層がハニカム基材表面に形成されてなる排ガス浄化用触
媒とすることが望ましい。[0010] Further, an exhaust gas purification method is provided in which a double-layered coating layer comprising a lower layer containing a first oxide carrier carrying an alkali metal and an upper layer containing a second oxide carrier carrying a noble metal is formed on the surface of a honeycomb substrate. Can be used as a catalyst for exhaust gas purification, but a coating layer in which a first oxide carrier powder supporting an alkali metal and a second oxide carrier powder supporting a noble metal are mixed is formed on the surface of a honeycomb substrate. It is desirable to use it as a catalyst.
【００１１】また、上記第１酸化物担体粉末と第２酸化
物担体粉末が混在したコート層がハニカム基材表面に形
成されてなる排ガス浄化用触媒を製造できる本発明の製
造方法の特徴は、高比表面積の第１酸化物担体粉末と、
低比表面積の第２酸化物担体粉末に貴金属を担持してな
る触媒粉末と、の混合粉末をハニカム基材の表面にウォ
ッシュコートし焼成してコート層を形成し、その後アル
カリ金属を担持することにある。[0011] Further, a feature of the production method of the present invention that can produce an exhaust gas purifying catalyst in which a coat layer in which the first oxide carrier powder and the second oxide carrier powder are mixed is formed on the surface of a honeycomb substrate is as follows. A first oxide carrier powder having a high specific surface area;
Washing and baking a mixed powder of a catalyst powder obtained by supporting a noble metal on a second oxide carrier powder having a low specific surface area on the surface of a honeycomb substrate to form a coat layer, and then supporting an alkali metal It is in.
【００１２】上記第１酸化物担体粉末と第２酸化物担体
粉末が混在したコート層がハニカム基材表面に形成され
てなる排ガス浄化用触媒を製造できる本発明のもう一つ
の製造方法の特徴は、高比表面積の第１酸化物担体粉末
にアルカリ金属の酒石酸水素塩を担持した粉末と、低比
表面積の第２酸化物担体粉末に貴金属を担持してなる触
媒粉末と、の混合粉末をハニカム基材の表面にウォッシ
ュコートし焼成してコート層を形成することにある。Another feature of the production method of the present invention that can produce an exhaust gas purifying catalyst in which a coat layer in which the first oxide carrier powder and the second oxide carrier powder are mixed is formed on the surface of a honeycomb substrate. A honeycomb formed by mixing a powder in which alkali metal hydrogen tartrate is supported on a first oxide carrier powder having a high specific surface area and a catalyst powder in which a noble metal is supported on a second oxide carrier powder having a low specific surface area is used as a honeycomb. It is to form a coat layer by wash-coating and baking on the surface of the substrate.
【００１３】上記第１酸化物担体粉末と第２酸化物担体
粉末が混在したコート層がハニカム基材表面に形成され
てなる排ガス浄化用触媒を製造できる本発明のさらにも
う一つの製造方法の特徴は、高比表面積の第１酸化物担
体粉末にアルカリ金属の酒石酸水素塩を担持した粉末
と、低比表面積の第２酸化物担体粉末と、の混合粉末を
ハニカム基材の表面にウォッシュコートしアルカリ金属
の酒石酸水素塩の分解温度以下の温度で乾燥してコート
層を形成する工程と、７を超え12未満の範囲にpHが制御
されたアンミン系貴金属溶液を用いてコート層に貴金属
を担持し焼成する工程と、をこの順に行うことにある。Still another feature of the present invention is a method for producing an exhaust gas purifying catalyst in which a coating layer in which the first oxide carrier powder and the second oxide carrier powder are mixed is formed on the surface of the honeycomb substrate. Washes a mixed powder of a powder in which alkali metal hydrogen tartrate is supported on a first oxide carrier powder having a high specific surface area and a second oxide carrier powder having a low specific surface area, and wash-coats the mixture on the surface of the honeycomb substrate. A step of forming a coat layer by drying at a temperature not higher than the decomposition temperature of the alkali metal hydrogen tartrate, and supporting the noble metal on the coat layer using an ammine-based noble metal solution whose pH is controlled in a range of more than 7 and less than 12 And firing step are performed in this order.
【００１４】上記二層構造のコート層がハニカム基材表
面に形成されてなる排ガス浄化用触媒が製造できる本発
明の製造方法の特徴は、ハニカム基材の表面に高比表面
積の第１酸化物担体粉末をウォッシュコートし焼成した
後にアルカリ金属を担持してアルカリ金属担持層を形成
する工程と、低比表面積の第２酸化物担体粉末に貴金属
を担持した粉末をアルカリ金属担持層の表面にウォッシ
ュコートし焼成して貴金属担持層を形成する工程と、を
この順に行うことにある。The method of the present invention for producing an exhaust gas purifying catalyst comprising the above-mentioned two-layered coating layer formed on the surface of a honeycomb substrate is characterized in that the first oxide having a high specific surface area is formed on the surface of the honeycomb substrate. A step of forming an alkali metal supporting layer by supporting an alkali metal after wash-coating and baking the carrier powder; and washing a powder obtained by supporting a noble metal on a second oxide carrier powder having a low specific surface area on the surface of the alkali metal supporting layer. Coating and baking to form a noble metal carrying layer.
【００１５】上記二層構造のコート層がハニカム基材表
面に形成されてなる排ガス浄化用触媒が製造できる本発
明のもう一つの製造方法の特徴は、ハニカム基材の表面
に高比表面積の第１酸化物担体粉末をウォッシュコート
し焼成した後にアルカリ金属の酒石酸水素塩を担持して
アルカリ金属担持層を形成する工程と、低比表面積の第
２酸化物担体粉末に貴金属を担持した粉末をアルカリ金
属担持層の表面にウォッシュコートし焼成して貴金属担
持層を形成する工程と、をこの順に行うことにある。Another feature of the production method of the present invention that can produce an exhaust gas purifying catalyst in which the above-described two-layered coating layer is formed on the surface of a honeycomb substrate is that the surface of the honeycomb substrate has a high specific surface area. (1) a step of forming an alkali metal supporting layer by supporting an alkali metal hydrogen tartrate after wash-coating and calcining the oxide carrier powder; And a step of wash-coating and firing the surface of the metal supporting layer to form a noble metal supporting layer.
【００１６】[0016]
【発明の実施の形態】本発明者らの研究によれば、比表
面積の異なる酸化物担体粉末の混合物に金属を含浸担持
すると、金属は高比表面積の酸化物担体に優先的に担持
されることが明らかとなった。また比表面積の異なる酸
化物担体にそれぞれアルカリ金属を担持させ、それに高
温耐久試験を行うと、高比表面積の酸化物担体に担持さ
れているアルカリ金属は低比表面積の酸化物担体へ移動
しにくいことも明らかとなった。本発明はこのような発
見に基づいてなされたものである。According to the study of the present inventors, when a metal is impregnated and supported on a mixture of oxide carrier powders having different specific surface areas, the metal is preferentially supported on the oxide carrier having a high specific surface area. It became clear. Also, when an alkali metal is supported on oxide carriers having different specific surface areas, respectively, and a high-temperature durability test is performed, the alkali metal supported on the oxide carrier having a high specific surface area hardly moves to the oxide carrier having a low specific surface area. It became clear. The present invention has been made based on such a finding.
【００１７】すなわち本発明の排ガス浄化用触媒では、
アルカリ金属を担持した第１酸化物担体の比表面積が、
貴金属を担持した第２酸化物担体の比表面積より大き
い。したがってこれらの混合物よりなる本発明の触媒で
は、高温耐久時にアルカリ金属が第２酸化物担体側へ移
動するのが防止され、高温耐久後もアルカリ金属と貴金
属は分離担持された状態を維持することができる。これ
により貴金属の粒成長が防止されるとともに、貴金属の
活性点がアルカリ金属で覆われるような不具合も防止さ
れるので、触媒活性の低下が抑制される。That is, in the exhaust gas purifying catalyst of the present invention,
The specific surface area of the first oxide carrier supporting the alkali metal is
It is larger than the specific surface area of the second oxide carrier supporting the noble metal. Therefore, in the catalyst of the present invention comprising these mixtures, the alkali metal is prevented from moving toward the second oxide carrier during high-temperature durability, and the alkali metal and the noble metal are kept separated and supported after high-temperature durability. Can be. This prevents grain growth of the noble metal and prevents a problem that the active site of the noble metal is covered with the alkali metal, so that a decrease in catalytic activity is suppressed.
【００１８】第１酸化物担体と第２酸化物担体の比表面
積の差は、30m2／ｇ以上であることが望ましい。比表面
積の差が30m2／ｇ未満では、高温耐久時に第１酸化物担
体に担持されているアルカリ金属が第２酸化物担体に移
動しやすくなり、貴金属の粒成長や活性の低下が生じて
しまう。比表面積の差の上限は特に制限されない。It is desirable that the difference between the specific surface areas of the first oxide carrier and the second oxide carrier is 30 m 2 / g or more. If the difference in specific surface area is less than 30 m 2 / g, the alkali metal carried on the first oxide carrier tends to move to the second oxide carrier during high-temperature durability, causing grain growth of the noble metal and reduction in activity. I will. The upper limit of the difference in specific surface area is not particularly limited.
【００１９】本発明の排ガス浄化用触媒の具体的な構成
として、例えばアルカリ金属を担持した第１酸化物担体
を含む下層と、貴金属を担持した第２酸化物担体を含む
上層とからなる二層構造のコート層がハニカム基材表面
に形成されてなる排ガス浄化用触媒とすることができ
る。この場合、アルカリ金属と貴金属とが二層に分かれ
て担持されているので、アルカリ金属の移動が防止され
る。As a specific configuration of the exhaust gas purifying catalyst of the present invention, for example, a two-layer structure comprising a lower layer containing a first oxide carrier carrying an alkali metal and an upper layer containing a second oxide carrier carrying a noble metal An exhaust gas purifying catalyst comprising a structured coat layer formed on the surface of a honeycomb substrate can be provided. In this case, the movement of the alkali metal is prevented because the alkali metal and the noble metal are supported in two layers.
【００２０】この二層構造のコート層を有する排ガス浄
化用触媒は、ハニカム基材の表面に高比表面積の第１酸
化物担体粉末をウォッシュコートし焼成した後にアルカ
リ金属を担持してアルカリ金属担持層を形成する工程
と、低比表面積の第２酸化物担体粉末に貴金属を担持し
た粉末をアルカリ金属担持層の表面にウォッシュコート
し焼成して貴金属担持層を形成する工程と、をこの順に
行うことで製造することができる。The exhaust gas purifying catalyst having the two-layered coat layer is prepared by wash-coating the surface of a honeycomb substrate with a first oxide carrier powder having a high specific surface area, calcining, and then supporting an alkali metal to support the alkali metal. The step of forming a layer and the step of wash-coating a powder obtained by supporting a noble metal on a second oxide carrier powder having a low specific surface area on the surface of an alkali metal supporting layer and firing the same to form a noble metal supporting layer are performed in this order. It can be manufactured by
【００２１】この第１の製造方法においては、貴金属担
持層を形成する工程において、アルカリ金属は高比表面
積の第１酸化物担体に担持されているので、アルカリ金
属がスラリー中に溶出しても第２酸化物担体に担持され
にくく再び第１酸化物担体に担持される。したがってア
ルカリ金属と貴金属とを容易かつ確実に分離担持するこ
とができる。ただし、スラリー中へ溶出したアルカリ金
属のうち第２酸化物担体に担持されるものも存在する。In the first production method, since the alkali metal is supported on the first oxide carrier having a high specific surface area in the step of forming the noble metal support layer, even if the alkali metal is eluted in the slurry, It is difficult to be carried on the second oxide carrier, and is again carried on the first oxide carrier. Therefore, the alkali metal and the noble metal can be easily and reliably separated and supported. However, some of the alkali metals eluted into the slurry are supported on the second oxide carrier.
【００２２】この二層構造のコート層を有する排ガス浄
化用触媒は、ハニカム基材の表面に高比表面積の第１酸
化物担体粉末をウォッシュコートし焼成した後にアルカ
リ金属の酒石酸水素塩を担持してアルカリ金属担持層を
形成する工程と、低比表面積の第２酸化物担体粉末に貴
金属を担持した粉末をアルカリ金属担持層の表面にウォ
ッシュコートし焼成して貴金属担持層を形成する工程
と、をこの順に行うことで製造することができる。The exhaust gas purifying catalyst having the two-layered coat layer is obtained by wash-coating the surface of a honeycomb substrate with a first oxide carrier powder having a high specific surface area and calcining the same, and then supporting an alkali metal hydrogen tartrate. Forming an alkali metal supporting layer, and a step of wash-coating the surface of the alkali metal supporting layer with a powder obtained by supporting a noble metal on a second oxide carrier powder having a low specific surface area and firing to form a noble metal supporting layer, In this order.
【００２３】この第２の製造方法においては、アルカリ
金属を酒石酸水素塩として担持し、貴金属担持層を形成
後に焼成して酒石酸成分を焼失させる方法を用いてい
る。アルカリ金属の酒石酸水素塩は水に難溶性であるの
で、貴金属担持層の形成時に水性の貴金属担持溶液及び
水性のスラリーに溶出し難く、アルカリ金属と貴金属と
を確実に分離担持することができる。In the second production method, a method is used in which an alkali metal is supported as a hydrogen tartaric acid salt, and a noble metal-supporting layer is formed and then fired to burn off the tartaric acid component. Since the alkali metal hydrogen tartrate is hardly soluble in water, it hardly dissolves in the aqueous noble metal supporting solution and the aqueous slurry when the noble metal supporting layer is formed, and the alkali metal and the noble metal can be reliably separated and supported.
【００２４】本発明の排ガス浄化用触媒は、アルカリ金
属を担持した第１酸化物担体粉末と、貴金属を担持した
第２酸化物担体粉末とが混在したコート層がハニカム基
材表面に形成されてなる排ガス浄化用触媒とすることが
好ましい。この構成の触媒では、上記したように、高温
耐久時にアルカリ金属が第２酸化物担体粉末側へ移動す
るのが防止されるので、触媒活性の低下を抑制すること
ができる。またコート層内では第１酸化物担体粒子と第
２酸化物担体粒子とが隣接しているため、これらに担持
されているアルカリ金属と貴金属とは互いに分離された
状態でありながら互いに近接している。したがって貴金
属の触媒作用によってNOが酸化されて生成するNO2 を速
やかにアルカリ金属で吸収することができ、触媒活性が
さらに向上する。The exhaust gas purifying catalyst of the present invention has a coating layer in which a first oxide carrier powder carrying an alkali metal and a second oxide carrier powder carrying a noble metal are formed on the surface of a honeycomb substrate. It is preferable to use an exhaust gas purifying catalyst. In the catalyst having this configuration, as described above, the alkali metal is prevented from moving toward the second oxide carrier powder during high-temperature durability, so that a decrease in catalytic activity can be suppressed. Further, since the first oxide carrier particles and the second oxide carrier particles are adjacent to each other in the coat layer, the alkali metal and the noble metal supported on these particles are close to each other while being separated from each other. I have. Therefore, NO 2 generated by oxidation of NO by the catalytic action of the noble metal can be quickly absorbed by the alkali metal, and the catalytic activity is further improved.
【００２５】さらに、この触媒の第１酸化物担体粉末及
び第２酸化物担体粉末の粒径は 0.5〜20μｍの範囲にあ
ることが好ましい。それぞれの粉末の粒径がこの範囲に
ある場合には、貴金属とアルカリ金属との分離と近接度
合いが最適となり、触媒活性がさらに向上する。Further, the particle diameter of the first oxide carrier powder and the second oxide carrier powder of the catalyst is preferably in the range of 0.5 to 20 μm. When the particle size of each powder is in this range, the degree of separation and proximity between the noble metal and the alkali metal is optimized, and the catalytic activity is further improved.
【００２６】このような排ガス浄化用触媒は、高比表面
積の第１酸化物担体粉末と、低比表面積の第２酸化物担
体粉末に貴金属を担持してなる触媒粉末との混合粉末を
ハニカム基材の表面にウォッシュコートし焼成してコー
ト層を形成し、その後アルカリ金属を含浸担持する方法
で製造することができる。Such an exhaust gas purifying catalyst is prepared by mixing a mixed powder of a first oxide carrier powder having a high specific surface area and a catalyst powder obtained by supporting a noble metal on a second oxide carrier powder having a low specific surface area. It can be manufactured by a method of wash-coating and baking a surface of a material to form a coat layer, and then impregnating and supporting an alkali metal.
【００２７】この第３の製造方法によれば、アルカリ金
属を含浸担持する際には、アルカリ金属は高比表面積の
第１酸化物担体粉末に優先して担持され、第２酸化物担
体粉末にはほとんど担持されない。したがってアルカリ
金属と貴金属とを容易に分離担持することができる。ま
たこの第３の製造方法によれば、アルカリ金属をコート
層の表面に高密度で担持することができ、活性がさらに
向上する効果が発現する。According to the third production method, when the alkali metal is impregnated and supported, the alkali metal is preferentially supported on the first oxide carrier powder having a high specific surface area, and the alkali metal is supported on the second oxide carrier powder. Is hardly supported. Therefore, the alkali metal and the noble metal can be easily separated and supported. According to the third manufacturing method, the alkali metal can be supported on the surface of the coat layer at a high density, and the effect of further improving the activity is exhibited.
【００２８】しかしながら上記第３の製造方法では、僅
かではあるものの第２酸化物担体に担持されてしまうア
ルカリ金属が存在する。したがって第１酸化物担体粉末
と第２酸化物担体粉末が混在したコート層を有する本発
明の排ガス浄化用触媒を製造する場合においても、アル
カリ金属を酒石酸水素塩として担持し、コート層を形成
後に焼成して酒石酸成分を焼失させる方法を用いること
が好ましい。However, in the above-mentioned third production method, there is a small amount of alkali metal which is supported on the second oxide carrier. Therefore, even when manufacturing the exhaust gas purifying catalyst of the present invention having a coat layer in which the first oxide carrier powder and the second oxide carrier powder are mixed, the alkali metal is supported as hydrogen tartrate, and after forming the coat layer, It is preferable to use a method of firing to burn off the tartaric acid component.
【００２９】すなわち本発明の第４の製造方法では、高
比表面積の第１酸化物担体粉末にアルカリ金属の酒石酸
水素塩を担持した粉末と、低比表面積の第２酸化物担体
粉末に貴金属を担持してなる触媒粉末と、の混合粉末を
ハニカム基材の表面にウォッシュコートし焼成してコー
ト層を形成している。That is, in the fourth production method of the present invention, a powder in which alkali metal hydrogen tartrate is supported on a first oxide carrier powder having a high specific surface area, and a noble metal is deposited on a second oxide carrier powder having a low specific surface area. A mixed powder of the supported catalyst powder and the mixed powder is wash-coated on the surface of the honeycomb substrate and fired to form a coat layer.
【００３０】高比表面積の第１酸化物担体粉末にアルカ
リ金属の酒石酸水素塩を担持するには、先ず通常の含浸
担持法などによってアルカリ金属を担持し、それを酒石
酸水溶液で処理すればよい。これによって担持されてい
るアルカリ金属が難溶性の酒石酸水素塩となり、ウォッ
シュコート時のスラリー中への溶出が防止される。した
がって上記第４の製造方法によれば、貴金属とアルカリ
金属とを確実に分離して担持することができる。In order to support the alkali metal hydrogen tartrate on the first oxide carrier powder having a high specific surface area, the alkali metal is first supported by a usual impregnation support method or the like, and the alkali metal is then treated with an aqueous tartaric acid solution. As a result, the supported alkali metal becomes hardly soluble bitartrate, and elution into the slurry during wash coating is prevented. Therefore, according to the fourth manufacturing method, the noble metal and the alkali metal can be reliably separated and supported.
【００３１】また高比表面積の第１酸化物担体粉末にア
ルカリ金属の酒石酸水素塩を担持した粉末と、低比表面
積の第２酸化物担体粉末と、の混合粉末をハニカム基材
の表面にウォッシュコートしアルカリ金属の酒石酸水素
塩の分解温度以下の温度で乾燥してコート層を形成する
工程と、７を超え12未満の範囲にpHが制御されたアンミ
ン系貴金属溶液を用いてコート層に貴金属を担持し焼成
する工程と、をこの順に行う方法でも本発明の排ガス浄
化用触媒を製造することができる。Further, a mixed powder of a powder in which an alkali metal hydrogen tartrate is supported on a first oxide carrier powder having a high specific surface area and a second oxide carrier powder having a low specific surface area is washed on the surface of the honeycomb substrate. Coating and drying at a temperature not higher than the decomposition temperature of the alkali metal hydrogen tartrate to form a coat layer, and using an ammine-based noble metal solution whose pH is controlled in the range of more than 7 and less than 12 to form a noble metal on the coat layer The catalyst for purifying exhaust gas of the present invention can also be produced by a method in which the steps of carrying and firing are carried out in this order.
【００３２】上記第５の製造方法において、７を超え12
未満の範囲にpHが制御されたアンミン系貴金属溶液を用
いると、アンミン系貴金属がアルカリ金属の酒石酸水素
塩を避けて低比表面積の第２酸化物担体粉末に担持され
るため、アルカリ金属を担持した後に貴金属を担持した
場合でも貴金属とアルカリ金属をさらに分離して担持す
ることができる。なお貴金属の担持時にはコート層にア
ルカリ金属の酒石酸水素塩が存在している必要があり、
コート層はその酒石酸水素塩が分解しない温度で乾燥す
る必要がある。その温度としては、約 200℃以下とする
のが好ましい。In the above-mentioned fifth manufacturing method, more than 7 and 12
When an ammine-based noble metal solution whose pH is controlled to a range of less than is used, the ammine-based noble metal is supported on the second oxide carrier powder having a low specific surface area while avoiding the alkali metal hydrogen tartrate, so Even when the noble metal is supported after the above, the noble metal and the alkali metal can be further separated and supported. When the noble metal is supported, the alkali metal bitartrate needs to be present in the coat layer.
The coat layer must be dried at a temperature at which the bitartrate does not decompose. The temperature is preferably about 200 ° C. or less.
【００３３】また第４の製造方法では、貴金属がコート
層内部にまで担持されているが、上記第５の製造方法に
よれば貴金属をコート層の表面に高密度で担持すること
ができ、活性がさらに向上する効果も発現される。In the fourth manufacturing method, the noble metal is carried to the inside of the coat layer. However, according to the fifth manufacturing method, the noble metal can be supported on the surface of the coat layer at a high density, and Is further improved.
【００３４】なおアンミン系貴金属溶液のpHを７を超え
12未満の範囲に制御するには、アンモニア水などの緩衝
溶液を用いて行えばよい。When the pH of the ammine precious metal solution exceeds 7,
In order to control it to a range of less than 12, a buffer solution such as aqueous ammonia may be used.
【００３５】ハニカム基材としては、コーディエライト
などの耐熱性セラミックスから形成されたもの、あるい
は金属箔製の波板と平板を交互に積層又は巻回して形成
されたものなど、従来用いられているものを用いること
ができる。As the honeycomb base material, a base material formed of a heat-resistant ceramic such as cordierite, or a base material formed by alternately laminating or winding a corrugated plate and a flat plate made of a metal foil and the like is used. Can be used.
【００３６】本発明の排ガス浄化用触媒における第１酸
化物担体及び第２酸化物担体としては、第１酸化物担体
が第２酸化物担体より相対的に高比表面積であればよ
く、γ-Al2O3、θ-Al2O3、ZrO2、TiO2、SiO2などの多孔
質酸化物から種々の組合せを選択することができる。例
えばγ-Al2O3は比表面積が特に高いので第１酸化物担体
として最適であり、この場合の第２酸化物担体としては
θ-Al2O3、ZrO2、TiO2、SiO2などから選択して用いるこ
とができる。As the first oxide carrier and the second oxide carrier in the exhaust gas purifying catalyst of the present invention, it is sufficient that the first oxide carrier has a relatively higher specific surface area than the second oxide carrier. Various combinations can be selected from porous oxides such as Al 2 O 3 , θ-Al 2 O 3 , ZrO 2 , TiO 2 , and SiO 2 . For example, γ-Al 2 O 3 is particularly suitable as the first oxide carrier because it has a particularly high specific surface area. In this case, the second oxide carrier is θ-Al 2 O 3 , ZrO 2 , TiO 2 , SiO 2, etc. It can be selected from and used.
【００３７】また担体粉末をウォッシュコートしてコー
ト層を形成するには、担体粉末にアルミナゾルなどのバ
インダと水を加えてスラリーを調製し、このスラリー中
にハニカム基材を浸漬し引き上げて乾燥・焼成すること
で形成することができる。In order to wash coat the carrier powder to form a coat layer, a slurry is prepared by adding a binder such as alumina sol and water to the carrier powder, and the honeycomb substrate is immersed in the slurry, pulled up and dried. It can be formed by firing.
【００３８】貴金属としては、Pt，Rh，Pd，Ir，Ruなど
から選択して用いることができる。このうち一種でもよ
いし、複数種類を担持することもできる。また貴金属の
担持量は、ハニカム基材１リットル当たり 0.1〜20ｇの
範囲とするのが好ましい。The noble metal can be selected from Pt, Rh, Pd, Ir, Ru and the like. Of these, one type may be used, or a plurality of types may be supported. The amount of the noble metal carried is preferably in the range of 0.1 to 20 g per liter of the honeycomb substrate.
【００３９】またアルカリ金属としては、Ｋ、Na、Cs、
Fr、Liから選択され、Ｋが特に好ましい。そしてアルカ
リ金属の担持量は、ハニカム基材１リットル当たり0.05
〜２モルの範囲が好ましい。なお本発明の排ガス浄化用
触媒には、アルカリ金属に加えてアルカリ土類金属ある
いは希土類元素を担持することも好ましい。このように
すれば低温域におけるNOx 浄化活性が向上する。As the alkali metals, K, Na, Cs,
It is selected from Fr and Li, and K is particularly preferred. The supporting amount of the alkali metal is 0.05 0.05 per liter of the honeycomb substrate.
A range of ~ 2 mol is preferred. The exhaust gas purifying catalyst of the present invention preferably supports an alkaline earth metal or a rare earth element in addition to the alkali metal. This improves the NO x purification activity in the low temperature range.
【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。The present invention will be specifically described below with reference to examples and comparative examples.
【００４１】（実施例１）比表面積 180m2／ｇ、平均粒
径約５μｍのγ-Al2O3粉末とアルミナゾルと水を混合し
てスラリーを調製した。次に直径30mm、長さ50mm、35c
c、セル数 400／in 2 のセラミックス製ハニカム基材を
用意し、上記スラリーに浸漬後引き上げて余分なスラリ
ーを除去した後、乾燥・焼成してコート層を形成した。
この工程を繰り返し、ハニカム基材１リットル当たり65
ｇのコート層を形成した。Example 1 Specific surface area: 180 mTwo/ G, average grain
Γ-Al with a diameter of about 5μmTwoOThreeMix the powder, alumina sol and water
To prepare a slurry. Next, diameter 30mm, length 50mm, 35c
c, cell number 400 / in Two Ceramic honeycomb substrate
Prepare, immerse in the above slurry and pull up to remove excess slurry
After removing the solvent, drying and firing were performed to form a coat layer.
This process is repeated to obtain 65 liters of honeycomb substrate per liter.
g coat layer was formed.
【００４２】これを 250℃で15分乾燥させた後、所定濃
度の硝酸カリウム水溶液の所定量を含浸させ、 250℃で
乾燥後 500℃で30分焼成してＫを担持した。Ｋの担持量
は、ハニカム基材１リットル当たり 0.2モルであった。This was dried at 250 ° C. for 15 minutes, impregnated with a predetermined amount of an aqueous solution of potassium nitrate having a predetermined concentration, dried at 250 ° C., and calcined at 500 ° C. for 30 minutes to carry K. The supported amount of K was 0.2 mol per liter of the honeycomb substrate.
【００４３】一方、比表面積 120m2／ｇ、平均粒径約４
μｍのZrO2粉末を用意し、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、 250℃で乾燥後 500℃
で30分焼成してPtを担持し、Pt／ZrO2粉末を調製した。
Pt／ZrO2粉末のPtの担持量は1.7重量％である。On the other hand, the specific surface area is 120 m 2 / g, and the average particle size is about 4
Prepare a ZrO 2 powder of μm, impregnate it with a predetermined amount of dinitrodiamine platinum aqueous solution of a predetermined concentration, dry at 250 ° C. and 500 ° C.
For 30 minutes to carry Pt and prepare a Pt / ZrO 2 powder.
The supported amount of Pt in the Pt / ZrO 2 powder was 1.7% by weight.
【００４４】そしてPt／ZrO2粉末とジルコニアゾル及び
水を混合してスラリーを調製し、Ｋを担持したコート層
をもつハニカム基材を浸漬後引き上げて余分なスラリー
を除去した後、乾燥・焼成してPt担持層を形成した。Pt
担持層は、ハニカム基材１リットル当たり55ｇ形成さ
れ、Ptの担持量はハニカム基材１リットル当たり２ｇで
ある。Then, a slurry is prepared by mixing Pt / ZrO 2 powder, zirconia sol and water, a honeycomb substrate having a coat layer carrying K is immersed, pulled up to remove excess slurry, and then dried and fired. Thus, a Pt carrying layer was formed. Pt
The supporting layer is formed in an amount of 55 g per liter of the honeycomb substrate, and the amount of Pt supported is 2 g per liter of the honeycomb substrate.
【００４５】（比較例１）比表面積 120m2／ｇ、平均粒
径約４μｍのZrO2粉末とジルコニアゾルと水を混合して
スラリーを調製した。次に実施例１と同様のセラミック
ス製ハニカム基材を用意し、上記スラリーに浸漬後引き
上げて余分なスラリーを除去した後、乾燥・焼成してコ
ート層を形成した。この工程を繰り返し、ハニカム基材
１リットル当たり65ｇのコート層を形成した。Comparative Example 1 A slurry was prepared by mixing ZrO 2 powder having a specific surface area of 120 m 2 / g and an average particle size of about 4 μm, zirconia sol and water. Next, the same ceramic honeycomb base material as in Example 1 was prepared, immersed in the slurry and pulled up to remove excess slurry, and then dried and fired to form a coat layer. This step was repeated to form a coat layer of 65 g per liter of the honeycomb substrate.
【００４６】これを 250℃で15分乾燥させた後、所定濃
度の硝酸カリウム水溶液の所定量を含浸させ、 250℃で
乾燥後 500℃で30分焼成してＫを担持した。Ｋの担持量
は、ハニカム基材１リットル当たり 0.2モルであった。This was dried at 250 ° C. for 15 minutes, impregnated with a predetermined amount of a potassium nitrate aqueous solution having a predetermined concentration, dried at 250 ° C., and calcined at 500 ° C. for 30 minutes to carry K. The supported amount of K was 0.2 mol per liter of the honeycomb substrate.
【００４７】一方、比表面積 180m2／ｇ、平均粒径約５
μｍのγ-Al2O3粉末を用意し、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、 250℃で乾燥後 5
00℃で30分焼成してPtを担持し、Pt／γ-Al2O3粉末を調
製した。Pt／γ-Al2O3粉末のPtの担持量は 1.7重量％で
ある。On the other hand, the specific surface area is 180 m 2 / g and the average particle size is about 5
Prepare a γ-Al 2 O 3 powder of μm, impregnate it with a predetermined amount of a dinitrodiamine platinum aqueous solution of a predetermined concentration, and dry at 250 ° C.
Pt was carried by baking at 00 ° C. for 30 minutes to prepare a Pt / γ-Al 2 O 3 powder. The supported amount of Pt in the Pt / γ-Al 2 O 3 powder was 1.7% by weight.
【００４８】そしてPt／γ-Al2O3粉末とアルミナゾル及
び水を混合してスラリーを調製し、Ｋを担持したコート
層をもつハニカム基材を浸漬後引き上げて余分なスラリ
ーを除去した後、乾燥・焼成してPt担持層を形成した。
Pt担持層は、ハニカム基材１リットル当たり55ｇ形成さ
れ、Ptの担持量はハニカム基材１リットル当たり２ｇで
ある。Then, a slurry is prepared by mixing Pt / γ-Al 2 O 3 powder, alumina sol and water, and after immersing a honeycomb substrate having a coat layer carrying K and pulling it up to remove excess slurry, It was dried and fired to form a Pt support layer.
The Pt carrying layer is formed in an amount of 55 g per liter of the honeycomb substrate, and the amount of Pt carried is 2 g per liter of the honeycomb substrate.
【００４９】（実施例２）比表面積 100m2／ｇ、平均粒
径約６μｍのθ-Al2O3粉末を用意し、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、 250℃で乾
燥後 500℃で30分焼成してPtを担持し、Pt／θ-Al2O3粉
末を調製した。Pt／θ-Al2O3粉末のPtの担持量は 1.5重
量％である。Example 2 A θ-Al 2 O 3 powder having a specific surface area of 100 m 2 / g and an average particle size of about 6 μm was prepared, impregnated with a predetermined amount of a dinitrodiamine platinum aqueous solution having a predetermined concentration, and dried at 250 ° C. Thereafter, the powder was baked at 500 ° C. for 30 minutes to carry Pt, thereby preparing a Pt / θ-Al 2 O 3 powder. The supported amount of Pt in the Pt / θ-Al 2 O 3 powder was 1.5% by weight.
【００５０】このPt／θ-Al2O3粉末と、比表面積 280m2
／ｇ、平均粒径約４μｍのγ-Al2O3粉末とを重量比で１
対１の比率で混合し、さらにアルミナゾルと水を加えて
スラリーを調製した。そして実施例１と同様のハニカム
基材に同様にしてウォッシュコートし焼成して、Ptを担
持したコート層をハニカム基材１リットル当たり 130ｇ
形成した。Ptの担持量はハニカム基材１リットル当たり
２ｇである。The Pt / θ-Al 2 O 3 powder and a specific surface area of 280 m 2
/ G, γ-Al 2 O 3 powder having an average particle size of about 4 μm in a weight ratio of 1
The mixture was mixed at a ratio of 1: 1, and alumina sol and water were further added to prepare a slurry. Then, the same honeycomb substrate as in Example 1 was wash-coated and baked in the same manner, and the coated layer carrying Pt was 130 g per liter of the honeycomb substrate.
Formed. The supported amount of Pt is 2 g per liter of the honeycomb substrate.
【００５１】これを 250℃で15分乾燥させた後、所定濃
度の硝酸カリウム水溶液の所定量を含浸させ、 250℃で
乾燥後 500℃で30分焼成してＫを担持した。Ｋの担持量
は、ハニカム基材１リットル当たり 0.2モルであった。This was dried at 250 ° C. for 15 minutes, impregnated with a predetermined amount of an aqueous solution of potassium nitrate having a predetermined concentration, dried at 250 ° C., and calcined at 500 ° C. for 30 minutes to carry K. The supported amount of K was 0.2 mol per liter of the honeycomb substrate.
【００５２】（実施例３）比表面積 100m2／ｇ、平均粒
径約６μｍのθ-Al2O3粉末に所定量のPtを含有するジニ
トロジアミン白金水溶液の所定量を含浸させ、これを乾
燥、焼成して、Ptを 1.5重量％担持したPt／θ-Al2O3粉
末を調製した。Example 3 A θ-Al 2 O 3 powder having a specific surface area of 100 m 2 / g and an average particle size of about 6 μm was impregnated with a predetermined amount of a dinitrodiamine platinum aqueous solution containing a predetermined amount of Pt, and dried. By calcining, a Pt / θ-Al 2 O 3 powder carrying 1.5% by weight of Pt was prepared.
【００５３】一方、比表面積 280m2／ｇ、平均粒径約４
μｍのγ-Al2O3粉末に所定濃度の硝酸カリウム水溶液の
所定量を含浸させ、これを 250℃で乾燥した後、十分な
量の酒石酸水溶液（濃度30重量％）に投入して室温で30
分間撹拌した。これを濾過後150℃で乾燥し、酒石酸水
素カリウムを43重量％担持した酒石酸水素Ｋ／γ-Al2O3
粉末を調製した。On the other hand, the specific surface area is 280 m 2 / g and the average particle size is about 4
μm γ-Al 2 O 3 powder is impregnated with a predetermined amount of a potassium nitrate aqueous solution having a predetermined concentration, dried at 250 ° C., poured into a sufficient amount of a tartaric acid aqueous solution (concentration: 30% by weight), and cooled at room temperature for 30 minutes.
Stirred for minutes. This was filtered, dried at 150 ° C., and hydrogen bitartrate K / γ-Al 2 O 3 carrying 43% by weight of potassium bitartrate
A powder was prepared.
【００５４】そしてPt／θ-Al2O3粉末と酒石酸水素Ｋ／
γ-Al2O3粉末とを重量比で１：１に混合し、さらにアル
ミナゾルと水を加えてスラリーを調製した。そして実施
例１と同様のハニカム基材に同様にしてウォッシュコー
トし、 500℃で30分焼成して、ハニカム基材１リットル
当たり130ｇのコート層を形成した。ハニカム基材１リ
ットル当たり、Ptは２ｇ、Ｋは 0.2モル担持されてい
る。Then, Pt / θ-Al 2 O 3 powder and hydrogen tartrate K /
γ-Al 2 O 3 powder was mixed at a weight ratio of 1: 1 and further a slurry was prepared by adding alumina sol and water. Then, the same honeycomb substrate as in Example 1 was wash-coated in the same manner and fired at 500 ° C. for 30 minutes to form a coat layer of 130 g per liter of the honeycomb substrate. 2 g of Pt and 0.2 mol of K are supported per liter of the honeycomb substrate.
【００５５】（実施例４）実施例３で調製された酒石酸
水素Ｋ／γ-Al2O3粉末と、比表面積 100m2／ｇ、平均粒
径約６μｍのθ-Al2O3粉末とを重量比で１：１に混合
し、さらにアルミナゾルと水を加えてスラリーを調製し
た。そして実施例１と同様のハニカム基材に同様にして
ウォッシュコートし、 200℃で30分乾燥して、ハニカム
基材１リットル当たり130ｇのコート層を形成した。コ
ート層には酒石酸水素カリウムが43重量％担持されてい
る。Example 4 The K / γ-Al 2 O 3 hydrogen bitartrate powder prepared in Example 3 was mixed with the θ-Al 2 O 3 powder having a specific surface area of 100 m 2 / g and an average particle size of about 6 μm. The mixture was mixed at a weight ratio of 1: 1 and further a slurry was prepared by adding alumina sol and water. Then, the same honeycomb substrate as in Example 1 was wash-coated in the same manner, and dried at 200 ° C. for 30 minutes to form a coat layer of 130 g per liter of the honeycomb substrate. The coat layer carries 43% by weight of potassium hydrogen tartrate.
【００５６】次にアンモニア水を用いてpHを10に制御し
たテトラアンミン白金水溶液に、上記コート層をもつハ
ニカム基材を浸漬し、引き上げて余分な液滴を吹き払っ
た後、 250℃で30分乾燥し 500℃で30分焼成した。ハニ
カム基材１リットル当たり、Ptは２ｇ、Ｋは 0.2モル担
持されている。Next, the honeycomb substrate having the above-mentioned coating layer was immersed in an aqueous tetraammineplatinum solution whose pH was controlled to 10 using aqueous ammonia, pulled up and blown off extra droplets. It was dried and baked at 500 ° C for 30 minutes. 2 g of Pt and 0.2 mol of K are supported per liter of the honeycomb substrate.
【００５７】（比較例２）比表面積 280m2／ｇ、平均粒
径約４μｍのγ-Al2O3粉末を用意し、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、 250℃で乾
燥後 500℃で30分焼成してPtを担持し、Pt／γ-Al2O3粉
末を調製した。Pt／γ-Al2O3粉末のPtの担持量は 1.5重
量％である。Comparative Example 2 A γ-Al 2 O 3 powder having a specific surface area of 280 m 2 / g and an average particle size of about 4 μm was prepared, impregnated with a predetermined amount of a dinitrodiamine platinum aqueous solution having a predetermined concentration, and dried at 250 ° C. Thereafter, it was baked at 500 ° C. for 30 minutes to carry Pt, thereby preparing Pt / γ-Al 2 O 3 powder. The supported amount of Pt in the Pt / γ-Al 2 O 3 powder was 1.5% by weight.
【００５８】このPt／γ-Al2O3粉末と、比表面積 100m2
／ｇ、平均粒径約６μｍのθ-Al2O3粉末とを重量比で１
対１の比率で混合し、さらにアルミナゾルと水を加えて
スラリーを調製した。そして実施例１と同様のハニカム
基材に同様にしてウォッシュコートし焼成して、Ptを担
持したコート層をハニカム基材１リットル当たり 130ｇ
形成した。Ptの担持量はハニカム基材１リットル当たり
２ｇである。The Pt / γ-Al 2 O 3 powder and a specific surface area of 100 m 2
/ G, and a θ-Al 2 O 3 powder having an average particle size of about 6 μm in a weight ratio of 1
The mixture was mixed at a ratio of 1: 1, and alumina sol and water were further added to prepare a slurry. Then, the same honeycomb substrate as in Example 1 was wash-coated and baked in the same manner, and the coated layer carrying Pt was 130 g per liter of the honeycomb substrate.
Formed. The supported amount of Pt is 2 g per liter of the honeycomb substrate.
【００５９】これを 250℃で15分乾燥させた後、所定濃
度の硝酸カリウム水溶液の所定量を含浸させ、 250℃で
乾燥後 500℃で30分焼成してＫを担持した。Ｋの担持量
は、ハニカム基材１リットル当たり 0.2モルであった。This was dried at 250 ° C. for 15 minutes, impregnated with a predetermined amount of an aqueous solution of potassium nitrate having a predetermined concentration, dried at 250 ° C., and calcined at 500 ° C. for 30 minutes to carry K. The supported amount of K was 0.2 mol per liter of the honeycomb substrate.
【００６０】（比較例３）比表面積 100m2／ｇのθ-Al2
O3粉末に代えて比表面積 280m2／ｇ、平均粒径約４μｍ
のγ-Al2O3粉末を用いたこと以外は実施例３と同様にし
て、比較例３の触媒を調製した。Comparative Example 3 θ-Al 2 having a specific surface area of 100 m 2 / g
Specific surface area 280m 2 / g, average particle size about 4μm instead of O 3 powder
The catalyst of Comparative Example 3 was prepared in the same manner as in Example 3 except that the γ-Al 2 O 3 powder was used.
【００６１】（比較例４）テトラアンミン白金水溶液に
代えてジニトロジアミン白金水溶液を用いたこと以外は
実施例４と同様にして、比較例４の触媒を調製した。Comparative Example 4 A catalyst of Comparative Example 4 was prepared in the same manner as in Example 4 except that an aqueous solution of dinitrodiamine platinum was used instead of the aqueous solution of tetraammineplatinum.
【００６２】＜試験例＞各触媒の構成を表１に示す。<Test Example> Table 1 shows the constitution of each catalyst.
【００６３】[0063]
【表１】 [Table 1]
【００６４】実施例１及び比較例１の触媒について、断
面のEPMA分析を行った。図１〜４に実施例１の触媒を、
図５〜８に比較例１の触媒を示す。図１〜８は本来カラ
ー画像であるが、白黒画像に変換して示している。各図
においては、図９に示す実施例１の触媒のようにハニカ
ム基材１と、下層２及び上層３の断面が見え、概して明
るい部分に各元素が多く存在しているが、カラー写真を
白黒に変換しているのでわかりにくい部分もある。The catalysts of Example 1 and Comparative Example 1 were subjected to EPMA analysis of the cross section. 1 to 4 show the catalyst of Example 1,
5 to 8 show the catalyst of Comparative Example 1. 1 to 8 are originally color images, but are shown after being converted to black and white images. In each figure, as in the catalyst of Example 1 shown in FIG. 9, the cross section of the honeycomb substrate 1, the lower layer 2 and the upper layer 3 can be seen, and there are many elements in generally bright portions. Some parts are difficult to understand because they are converted to black and white.
【００６５】実施例１の触媒では、Ｋは Al2O3からなる
下層２全体に均一に担持され、PtはZrO2からなる上層３
に均一に担持されていた。また上層３にはＫはほとんど
存在していなかった。つまり、ＫとPtとは分離担持され
ていることが確認された。In the catalyst of Example 1, K is uniformly supported on the entire lower layer 2 made of Al 2 O 3 , and Pt is deposited on the upper layer 3 made of ZrO 2.
Was uniformly supported. Also, almost no K was present in the upper layer 3. That is, it was confirmed that K and Pt were separately supported.
【００６６】一方比較例１の触媒では、Ptはγ-Al2O3よ
りなる上層３に均一に担持されているが、ＫはZrO2より
なる下層２よりもγ-Al2O3よりなる上層３に多く担持さ
れていることが認められた。つまり、上層ではPtとＫと
が近接して担持されていることが確認された。On the other hand, in the catalyst of Comparative Example 1, Pt is uniformly supported on the upper layer 3 made of γ-Al 2 O 3, but K is made of γ-Al 2 O 3 than the lower layer 2 made of ZrO 2. It was recognized that a large amount was carried on the upper layer 3. That is, it was confirmed that Pt and K were carried close to each other in the upper layer.
【００６７】これは、比較例１の触媒では、上層３のγ
-Al2O3の方が下層２のZrO2より比表面積が高いために、
上層３を形成するときに下層２に担持されていたＫがス
ラリーに溶出して移動して、上層３のγ-Al2O3に担持さ
れたと考えられる。しかし実施例１では、下層２のγ-A
l2O3の方が上層３のZrO2より比表面積が高いので、上層
３の形成時に下層２に担持されていたＫがスラリーに溶
出しても、再び下層２のγ-Al2O3に担持されたと考えら
れる。This is because, in the catalyst of Comparative Example 1, the γ
-Al 2 O 3 has a higher specific surface area than ZrO 2 of the lower layer 2,
It is considered that K carried on the lower layer 2 when forming the upper layer 3 eluted and moved into the slurry, and was carried on γ-Al 2 O 3 of the upper layer 3. However, in Example 1, γ-A
Since l 2 O 3 has a higher specific surface area than ZrO 2 of the upper layer 3, even if K supported on the lower layer 2 elutes into the slurry when the upper layer 3 is formed, the γ-Al 2 O 3 It is considered to be carried on.
【００６８】次に、実施例１〜４及び比較例１〜４の触
媒をそれぞれ評価装置に配置し、表２に示すモデルガス
を総流量30Ｌ／分、Lean／Rich＝55秒／５秒で交互に繰
り返し流しながら、 300〜 600℃の各温度における飽和
NOx 吸蔵量をそれぞれ測定した。結果を図10，図12，図
14及び図16に示す。Next, the catalysts of Examples 1 to 4 and Comparative Examples 1 to 4 were respectively placed in the evaluation device, and the model gas shown in Table 2 was supplied at a total flow rate of 30 L / min, Lean / Rich = 55 seconds / 5 seconds. Saturate at each temperature between 300 and 600 ° C while alternately flowing
The NO x storage amount was measured. The results are shown in Figs.
This is shown in FIG. 14 and FIG.
【００６９】なお飽和NOx 吸蔵量とは、吸蔵されたNOx
をRich雰囲気で充分還元した後にLean雰囲気としたとき
から、触媒出ガスNOx 濃度が触媒入りガスNOx 濃度に
達するまでの間に、触媒中に吸蔵された全NOx 量をいう
また実施例１〜４及び比較例１〜４の触媒をそれぞれ評
価装置に配置し、表３に示すモデルガスを総流量30Ｌ／
分、Lean／Rich＝55秒／５秒で交互に繰り返し流しなが
ら 800℃で４時間保持する耐久試験を行った。耐久試験
後の各触媒について、上記と同様にして飽和NOx 吸蔵量
を測定し、結果を図11，図13，図15及び図17に示す。Note that the saturated NO x storage amount is the stored NO x
From when the Lean atmosphere after sufficient reduction in Rich atmosphere, until the catalyst outlet gas concentration of NO x reaches the catalyst entering gas concentration of NO x refers to the total amount of NO x occluded in the catalyst also Example Each of the catalysts of Examples 1 to 4 and Comparative Examples 1 to 4 was placed in an evaluation device, and the model gas shown in Table 3 was supplied at a total flow rate of 30 L /
An endurance test was conducted at 800 ° C. for 4 hours while alternately and repeatedly flowing at a rate of Lean / Rich = 55 seconds / 5 seconds. For each of the catalysts after the durability test, the saturated NO x storage amount was measured in the same manner as above, and the results are shown in FIGS. 11, 13, 15, and 17.
【００７０】[0070]
【表２】 [Table 2]
【００７１】[0071]
【表３】 [Table 3]
【００７２】＜評価１＞図10より、実施例１の触媒は比
較例１の触媒に比べて初期の飽和NOx 吸蔵量が多い。す
なわち実施例１の触媒は、比較例１の触媒よりもPtの活
性が高いことが明らかであり、これは実施例１の触媒で
は、ＫによってPtの活性点が覆われている確率が小さい
ためと考えられる。<Evaluation 1> As shown in FIG. 10, the catalyst of Example 1 has a larger initial saturated NO x storage amount than the catalyst of Comparative Example 1. That is, it is clear that the catalyst of Example 1 has a higher Pt activity than the catalyst of Comparative Example 1. This is because the probability of the active point of Pt being covered by K is small in the catalyst of Example 1. it is conceivable that.
【００７３】また図11より、実施例１の触媒は比較例１
の触媒に比べて耐久後の飽和NOx 吸蔵量が多い。これ
は、実施例１の触媒では、Ｋの移動によってPtの活性点
が覆われる確率が小さく、かつＫとの相互作用によるPt
の粒成長も抑制されているためと考えられる。FIG. 11 shows that the catalyst of Example 1 was the same as that of Comparative Example 1
The saturated NO x storage amount after the endurance is larger than that of the catalyst of No. This is because in the catalyst of Example 1, the probability that the active site of Pt is covered by the movement of K is small, and Pt due to the interaction with K
It is considered that the grain growth was also suppressed.
【００７４】すなわちＫを下層に担持し、その後にPtを
担持した上層を形成する場合には、各層の担体の比表面
積によって活性が大きく異なり、Ｋを担持する担体の比
表面積が上層の担体の比表面積より大きいことが望まし
いことが明らかである。That is, when K is carried on the lower layer and then the upper layer carrying Pt is formed, the activity varies greatly depending on the specific surface area of the carrier of each layer, and the specific surface area of the carrier carrying K is higher than that of the upper carrier. It is clear that it is desirable to have a specific surface area larger than that.
【００７５】＜評価２＞実施例３及び比較例３の触媒の
初期における飽和NOx 吸蔵量を図12に、耐久後の飽和NO
x 吸蔵量を図13に示す。実施例３と比較例３の触媒は、
Ptが担持されている担体だけが異なっている。<Evaluation 2> The saturated NO x storage amount of the catalysts of Example 3 and Comparative Example 3 in the initial stage is shown in FIG.
The x storage amount shown in Fig. 13. The catalysts of Example 3 and Comparative Example 3 were:
Only the carrier on which Pt is carried is different.
【００７６】図12及び図13より、実施例３の触媒は比較
例３の触媒に比べて初期及び耐久後ともに飽和NOx 吸蔵
量が多い。これは、比較例３の触媒では、Ptを担持した
担体と酒石酸水素カリウムを担持した担体との比表面積
の差が無いために、耐久試験時の温度雰囲気ばかりでな
く初期の飽和NOx 吸蔵量測定時の温度雰囲気でもＫの移
動が生じ、Ｋによって覆われるPtが多くなったためと考
えられる。12 and 13, the catalyst of Example 3 has a larger saturated NO x storage amount both at the initial stage and after the endurance than the catalyst of Comparative Example 3. This is, in the catalyst of Comparative Example 3, because the difference in specific surface area of the carrier supporting the carrier and potassium bitartrate carrying Pt is not, the initial saturated the NO x storage amount not only temperature atmosphere during endurance test It is considered that the movement of K occurred even in the temperature atmosphere at the time of measurement, and that Pt covered by K increased.
【００７７】＜評価３＞実施例２〜４と比較例２，４の
初期における飽和NOx 吸蔵量を図14に、耐久後の飽和NO
x 吸蔵量を図15に示す。各実施例の触媒は各比較例の触
媒に比べて初期及び耐久後ともに高い飽和NOx 吸蔵量を
示している。これは、各実施例の触媒では比表面積の大
きな担体にＫが担持され、比表面積の小さな担体にPtが
担持されていることが最大の原因であると考えられる。<Evaluation 3> FIG. 14 shows the saturated NO x occlusion amount of Examples 2 to 4 and Comparative Examples 2 and 4 at the initial stage.
FIG. 15 shows the x storage amounts. The catalysts of the respective examples show a higher saturated NO x storage amount both at the initial stage and after the endurance than the catalysts of the respective comparative examples. This is considered to be mainly due to the fact that K is supported on a carrier having a large specific surface area and Pt is supported on a carrier having a small specific surface area in the catalysts of the examples.
【００７８】また比較例４の触媒は実施例４の触媒に比
べて初期及び耐久後ともに飽和NOx吸蔵量が少ない。こ
れは、比較例４の触媒では、Ptがγ-Al2O3粉末に優先的
に担持されてＫと近接担持され、耐久試験時の温度雰囲
気ばかりでなく初期の飽和NO x 吸蔵量測定時の温度雰囲
気でもＫの移動が生じ、Ｋによって覆われるPtが多くな
ったためと考えられる。Further, the catalyst of Comparative Example 4 was compared with the catalyst of Example 4.
Saturated NO for both initial and endurancexLow storage capacity. This
This is because in the catalyst of Comparative Example 4, Pt was γ-AlTwoOThreePrefer to powder
Supported in close proximity to K, temperature atmosphere during endurance test
Initial saturation NO as well as mind x Temperature atmosphere when measuring occlusion amount
The movement of K occurs in the air, and the amount of Pt covered by K increases.
It is thought that it was.
【００７９】そして各実施例どうしを比較すると、初期
は実施例２及び実施例４が実施例３より飽和NOx 吸蔵量
が多く、耐久後は実施例４，実施例３，実施例２の順に
飽和NOx 吸蔵量が少なくなっている。実施例４は初期及
び耐久後ともに飽和NOx 吸蔵量が多く、実施例２は耐久
試験によって飽和NOx 吸蔵量が比較的大きく低下してい
る。When comparing the examples, Examples 2 and 4 have a larger saturated NO x storage amount than Example 3 at the initial stage, and Examples 4, 4 and 3 after the endurance. The saturated NO x storage amount is low. Example 4 Many initial and both saturated the NO x storage amount after the durability, Examples 2 saturated the NO x storage amount by the durability test is relatively large decrease.
【００８０】実施例２では硝酸カリウムを最後に担持し
ているため、θ-Al2O3粒子にはPtとともにある程度のＫ
が担持されている。一方の実施例４では、酒石酸水素カ
リウムが担持されているコート層にテトラアンミン白金
を用いてPtを担持しているため、酒石酸水素カリウムを
避けてPtがθ-Al2O3粒子に優先的に担持される。したが
って実施例４では、PtとＫとは異なる担体粒子にそれぞ
れ担持されたこととなり、これによって初期及び耐久後
にも高い飽和NOx 吸蔵量を示すと考えられる。In Example 2, since potassium nitrate is supported last, the K-Al 2 O 3 particles have a certain amount of K together with Pt.
Is carried. On the other hand, in Example 4, Pt was supported using tetraammine platinum in the coat layer on which potassium hydrogen tartrate was supported, so that Pt was preferentially given to θ-Al 2 O 3 particles avoiding potassium hydrogen tartrate. It is carried. Therefore, in Example 4, Pt and K were each supported on different carrier particles, and it is considered that this shows a high saturated NO x storage amount even at the initial stage and after the endurance.
【００８１】＜評価４＞実施例１と実施例２の初期にお
ける飽和NOx 吸蔵量を図16に、耐久後の飽和NO x 吸蔵量
を図17に示す。実施例２の触媒は実施例１の触媒に比べ
て初期及び耐久後ともに高い飽和NOx 吸蔵量を示してい
る。したがってPtとＫをコート層で分離して担持するよ
り、同一コート層内で異なる担体粒子にそれぞれ担持す
るのが好ましく、PtとＫとは互いに分離されながらも互
いに近接して担持されていることが特に望ましいことが
わかる。<Evaluation 4> At the beginning of Examples 1 and 2,
NOx The storage amount is shown in Fig. 16, and the saturated NO x Occlusion amount
Is shown in FIG. The catalyst of Example 2 is different from the catalyst of Example 1
High saturation NO both at initial and after endurancex Indicates the amount of occlusion
You. Therefore, Pt and K are separately supported by the coat layer.
Different carrier particles in the same coat layer.
Preferably, Pt and K are separated from each other,
It is particularly desirable that the
Understand.
【００８２】[0082]
【発明の効果】すなわち本発明の排ガス浄化用触媒によ
れば、比表面積の異なる第１酸化物担体と第２酸化物担
体を用いているため、アルカリ金属と貴金属を互いに分
離して担持することが可能となり、アルカリ金属の移動
による貴金属の活性低下を抑制することができる。According to the exhaust gas purifying catalyst of the present invention, since the first oxide carrier and the second oxide carrier having different specific surface areas are used, the alkali metal and the noble metal can be separately supported. And the reduction in the activity of the noble metal due to the movement of the alkali metal can be suppressed.
【００８３】そして第１酸化物担体と第２酸化物担体と
からそれぞれコート層を形成した二層構造とすれば、貴
金属とアルカリ金属を確実に分離担持でき、貴金属の活
性低下を抑制することができる。If the first oxide carrier and the second oxide carrier each have a two-layer structure in which a coat layer is formed, the noble metal and the alkali metal can be surely separated and supported, and a decrease in the activity of the noble metal can be suppressed. it can.
【００８４】さらに第１酸化物担体と第２酸化物担体と
が混在したコート層とすれば、貴金属とアルカリ金属を
互いに分離して担持しつつ互いに近接した状態とするこ
とができる。これによりNOx を効率よく吸蔵でき、上記
効果と相まって初期から高温耐久後まで高いNOx 浄化活
性が得られ、貴金属の活性を最大限に引き出すことがで
きる。Further, if a coat layer in which the first oxide carrier and the second oxide carrier are mixed is used, the noble metal and the alkali metal can be separated from each other and carried, and can be in the state of being close to each other. As a result, NO x can be stored efficiently, and in combination with the above effects, high NO x purification activity can be obtained from the initial stage to after high-temperature durability, and the activity of the noble metal can be maximized.
【００８５】そして本発明の排ガス浄化用触媒の製造方
法によれば、上記したような特性をもつ排ガス浄化用触
媒を容易にかつ確実に製造することができる。According to the method for producing an exhaust gas purifying catalyst of the present invention, an exhaust gas purifying catalyst having the above-mentioned characteristics can be produced easily and reliably.
【図１】実施例１の触媒の断面におけるPtの分布を示す
EPMA図である。FIG. 1 shows the distribution of Pt in the cross section of the catalyst of Example 1.
It is an EPMA diagram.
【図２】実施例１の触媒の断面におけるZrの分布を示す
EPMA図である。FIG. 2 shows a distribution of Zr in a cross section of the catalyst of Example 1.
It is an EPMA diagram.
【図３】実施例１の触媒の断面におけるAlの分布を示す
EPMA図である。FIG. 3 shows a distribution of Al in a cross section of the catalyst of Example 1.
It is an EPMA diagram.
【図４】実施例１の触媒の断面におけるＫの分布を示す
EPMA図である。FIG. 4 shows the distribution of K in the cross section of the catalyst of Example 1.
It is an EPMA diagram.
【図５】比較例１の触媒の断面におけるPtの分布を示す
EPMA図である。FIG. 5 shows the distribution of Pt in the cross section of the catalyst of Comparative Example 1.
It is an EPMA diagram.
【図６】比較例１の触媒の断面におけるAlの分布を示す
EPMA図である。FIG. 6 shows a distribution of Al in a cross section of the catalyst of Comparative Example 1.
It is an EPMA diagram.
【図７】比較例１の触媒の断面におけるZrの分布を示す
EPMA図である。FIG. 7 shows the distribution of Zr in the cross section of the catalyst of Comparative Example 1.
It is an EPMA diagram.
【図８】比較例１の触媒の断面におけるＫの分布を示す
EPMA図である。FIG. 8 shows the distribution of K in the cross section of the catalyst of Comparative Example 1.
It is an EPMA diagram.
【図９】EPMA図の構成を説明する実施例１の触媒の要部
断面図である。FIG. 9 is a cross-sectional view of a main part of the catalyst of Example 1, illustrating the configuration of the EPMA diagram.
【図10】実施例１及び比較例１の触媒の初期飽和NOx 吸
蔵量を示すグラフである。FIG. 10 is a graph showing the initial saturated NO x storage amounts of the catalysts of Example 1 and Comparative Example 1.
【図11】実施例１及び比較例１の触媒の耐久後飽和NOx
吸蔵量を示すグラフである。FIG. 11 shows saturated NO x after endurance of the catalysts of Example 1 and Comparative Example 1.
It is a graph which shows the occlusion amount.
【図12】実施例３及び比較例３の触媒の初期飽和NOx 吸
蔵量を示すグラフである。FIG. 12 is a graph showing initial saturated NO x storage amounts of catalysts of Example 3 and Comparative Example 3.
【図13】実施例３及び比較例３の触媒の耐久後飽和NOx
吸蔵量を示すグラフである。FIG. 13 shows saturated NO x after endurance of the catalysts of Example 3 and Comparative Example 3.
It is a graph which shows the occlusion amount.
【図14】実施例２〜４及び比較例２，４の触媒の初期飽
和NOx 吸蔵量を示すグラフである。FIG. 14 is a graph showing initial saturated NO x storage amounts of catalysts of Examples 2 to 4 and Comparative Examples 2 and 4.
【図15】実施例２〜４及び比較例２，４の触媒の耐久後
飽和NOx 吸蔵量を示すグラフである。FIG. 15 is a graph showing the saturated NO x storage amounts after endurance of the catalysts of Examples 2 to 4 and Comparative Examples 2 and 4.
【図16】実施例１及び実施例２の触媒の初期飽和NOx 吸
蔵量を示すグラフである。FIG. 16 is a graph showing the initial saturated NO x storage amounts of the catalysts of Example 1 and Example 2.
【図17】実施例１及び実施例２の触媒の耐久後飽和NOx
吸蔵量を示すグラフである。FIG. 17 shows the saturated NO x after endurance of the catalysts of Example 1 and Example 2.
It is a graph which shows the occlusion amount.
１：ハニカム基材 ２：下層 ３：上層 1: Honeycomb substrate 2: Lower layer 3: Upper layer
───────────────────────────────────────────────────── 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 37/02 １０１ Ｂ０１Ｊ 37/02 ３０１Ｄ ３０１ 37/04 １０１ 37/08 37/04 １０１ Ｆ０１Ｎ 3/08 Ａ 37/08 3/10 Ａ Ｆ０１Ｎ 3/08 3/28 ３０１Ｃ 3/10 ３０１Ｐ 3/28 ３０１ Ｂ０１Ｄ 53/36 １０４Ａ ＺＡＢ １０２Ｈ Ｆターム(参考） 3G091 AA02 AB06 BA14 GA06 GA16 GB02Y GB03Y GB04Y GB05W GB06W GB07W 4D048 AA06 AA13 AA18 AB05 AB07 BA03X BA08X BA14X BA30X BA31Y BA32Y BA33Y BA34Y BA41X BB02 BB16 BB17 CC36 CC46 CC50 EA04 4G069 AA03 AA08 BA01B BA05B BB04A BC01A BC01C BC03B BC32A BC33A BC69A BC75B BE08C BE44C CA02 CA03 CA09 CA13 DA06 EA19 EB18X EB18Y EC01X EC22Y EE06 EE09 FA01 FA02 FA03 FB07 FB14 FB19 FB23 FB30 FC02 FC07 FC09 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 Identification code FI Theme coat ゛ (Reference) B01J 37/02 101 B01J 37/02 301D 301 37/04 101 37/08 37/04 101 F01N 3/08 A 37/08 3/10 A F01N 3/08 3/28 301C 3/10 301P 3/28 301 B01D 53/36 104A ZAB 102H F term (reference) 3G091 AA02 AB06 BA14 GA06 GA16 GB02Y GB03Y GB04Y GB05W GB06W GB07W 4D048 AA06 AA13 AA18 AB05 AB07 BA03X BA08X BA14X BA30X BA31Y BA32Y BA33Y BA34Y BA41X BB02 BB16 BB17 CC36 CC46 CC50 EA04 4G069 AA03 AA08 BA01B BA05B BB04A BC01A BC01C BC03B BC32. FB14 FB19 FB23 FB30 FC02 FC07 FC09
Claims (10)
と、貴金属を担持した第２酸化物担体とよりなり、該第
１酸化物担体の比表面積が該第２酸化物担体の比表面積
より大きいことを特徴とする排ガス浄化用触媒。1. A first oxide carrier carrying an alkali metal and a second oxide carrier carrying a noble metal, wherein the specific surface area of the first oxide carrier is greater than the specific surface area of the second oxide carrier. An exhaust gas purifying catalyst characterized by being large.
体の比表面積の差が30m2／ｇ以上であることを特徴とす
る請求項１に記載の排ガス浄化用触媒。2. The exhaust gas purifying catalyst according to claim 1, wherein a difference in specific surface area between the first oxide carrier and the second oxide carrier is 30 m 2 / g or more.
担体粉末と、貴金属を担持した前記第２酸化物担体粉末
とが混在したコート層がハニカム基材表面に形成されて
なることを特徴とする請求項１に記載の排ガス浄化用触
媒。3. A coating layer comprising a mixture of the first oxide carrier powder carrying an alkali metal and the second oxide carrier powder carrying a noble metal is formed on the surface of a honeycomb substrate. The exhaust gas purifying catalyst according to claim 1, wherein
化物担体粉末の粒径が 0.5〜20μｍの範囲にあることを
特徴とする請求項３に記載の排ガス浄化用触媒。4. The exhaust gas purifying catalyst according to claim 3, wherein the particle diameters of the first oxide carrier powder and the second oxide carrier powder are in a range of 0.5 to 20 μm.
担体を含む下層と貴金属を担持した前記第２酸化物担体
を含む上層とからなる二層構造のコート層がハニカム基
材表面に形成されてなることを特徴とする請求項１に記
載の排ガス浄化用触媒。5. A two-layered coating layer comprising a lower layer containing the first oxide carrier carrying an alkali metal and an upper layer containing the second oxide carrier carrying a noble metal is formed on the surface of the honeycomb substrate. The exhaust gas purifying catalyst according to claim 1, wherein the catalyst comprises:
比表面積の第２酸化物担体粉末に貴金属を担持してなる
触媒粉末と、の混合粉末をハニカム基材の表面にウォッ
シュコートし焼成してコート層を形成し、その後アルカ
リ金属を担持することを特徴とする排ガス浄化用触媒の
製造方法。6. A method for wash-coating a mixture of a first oxide carrier powder having a high specific surface area and a catalyst powder comprising a noble metal supported on a second oxide carrier powder having a low specific surface area on the surface of a honeycomb substrate. And baking to form a coat layer, and then supporting an alkali metal.
カリ金属の酒石酸水素塩を担持した粉末と、低比表面積
の第２酸化物担体粉末に貴金属を担持してなる触媒粉末
と、の混合粉末をハニカム基材の表面にウォッシュコー
トし焼成してコート層を形成することを特徴とする排ガ
ス浄化用触媒の製造方法。7. A powder comprising a high specific surface area of a first oxide carrier powder carrying an alkali metal hydrogen tartrate and a catalyst powder comprising a low specific surface area of a second oxide carrier powder carrying a noble metal. A method for producing an exhaust gas purifying catalyst, comprising wash-coating a mixed powder on the surface of a honeycomb substrate and baking to form a coat layer.
カリ金属の酒石酸水素塩を担持した粉末と、低比表面積
の第２酸化物担体粉末と、の混合粉末をハニカム基材の
表面にウォッシュコートし該アルカリ金属の酒石酸水素
塩の分解温度以下の温度で乾燥してコート層を形成する
工程と、７を超え12未満の範囲にpHが制御されたアンミ
ン系貴金属溶液を用いて該コート層に貴金属を担持し焼
成する工程と、をこの順に行うことを特徴とする排ガス
浄化用触媒の製造方法。8. A mixed powder of a powder in which alkali metal hydrogen tartrate is supported on a first oxide carrier powder having a high specific surface area and a second oxide carrier powder having a low specific surface area is coated on the surface of the honeycomb substrate. Wash-coating and drying at a temperature not higher than the decomposition temperature of the alkali metal hydrogen tartrate to form a coating layer; and coating the coating with an ammine-based noble metal solution whose pH is controlled in the range of more than 7 and less than 12. A step of supporting a layer with a noble metal and calcining the layers in this order.
酸化物担体粉末をウォッシュコートし焼成した後にアル
カリ金属を担持してアルカリ金属担持層を形成する工程
と、低比表面積の第２酸化物担体粉末に貴金属を担持し
た粉末を該アルカリ金属担持層の表面にウォッシュコー
トし焼成して貴金属担持層を形成する工程と、をこの順
に行うことを特徴とする排ガス浄化用触媒の製造方法。9. A first substrate having a high specific surface area on a surface of a honeycomb substrate.
A step of forming an alkali metal supporting layer by supporting an alkali metal after wash-coating and calcining the oxide carrier powder; and forming a powder supporting the noble metal on the second oxide carrier powder having a low specific surface area by forming the alkali metal supporting layer. A step of wash-coating the surface and firing to form a noble metal-supported layer in this order.
酸化物担体粉末をウォッシュコートし焼成した後にアル
カリ金属の酒石酸水素塩を担持してアルカリ金属担持層
を形成する工程と、低比表面積の第２酸化物担体粉末に
貴金属を担持した粉末を該アルカリ金属担持層の表面に
ウォッシュコートし焼成して貴金属担持層を形成する工
程と、をこの順に行うことを特徴とする排ガス浄化用触
媒の製造方法。10. A high specific surface area first surface on a surface of a honeycomb substrate.
A step of wash-coating the oxide carrier powder and calcining the mixture to form an alkali metal-supporting layer by supporting an alkali metal hydrogen tartrate; and forming a powder having a noble metal supported on a second oxide carrier powder having a low specific surface area by the alkali. A process of wash-coating and firing the surface of the metal support layer to form a noble metal support layer in this order.
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| JP2001294609A JP4992172B2 (en) | 2000-10-16 | 2001-09-26 | Exhaust gas purification catalyst and method for producing the same |
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| JP2000315408 | 2000-10-16 | ||
| JP2000-315408 | 2000-10-16 | ||
| JP2000315408 | 2000-10-16 | ||
| JP2001294609A JP4992172B2 (en) | 2000-10-16 | 2001-09-26 | Exhaust gas purification catalyst and method for producing the same |
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| JP2002191989A true JP2002191989A (en) | 2002-07-10 |
| JP4992172B2 JP4992172B2 (en) | 2012-08-08 |
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| WO2012077510A1 (en) * | 2010-12-06 | 2012-06-14 | ヤマハ発動機株式会社 | Production method for exhaust gas-purifying catalyst and motor vehicle |
| US8258075B2 (en) | 2007-02-06 | 2012-09-04 | Mitsubishi Heavy Industries, Ltd. | Catalyst for treating exhaust gases, method for producing the same, and method for treating exhaust gases |
| CN105728025A (en) * | 2016-01-27 | 2016-07-06 | 中国石油天然气集团公司 | Catalytic cracking regenerated flue gas denitration catalyst as well as preparation method and application thereof |
| JP2018023924A (en) * | 2016-08-09 | 2018-02-15 | トヨタ自動車株式会社 | METHOD FOR PRODUCING NOx STORAGE-REDUCTION CATALYST |
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| CN105728025A (en) * | 2016-01-27 | 2016-07-06 | 中国石油天然气集团公司 | Catalytic cracking regenerated flue gas denitration catalyst as well as preparation method and application thereof |
| JP2018023924A (en) * | 2016-08-09 | 2018-02-15 | トヨタ自動車株式会社 | METHOD FOR PRODUCING NOx STORAGE-REDUCTION CATALYST |
| US9987593B2 (en) | 2016-08-09 | 2018-06-05 | Toyota Jidosha Kabushiki Kaisha | Method for producing NOx storage-reduction catalyst |
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|---|---|
| JP4992172B2 (en) | 2012-08-08 |
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