JPH08257407A - Catalyst for cleaning exhaust gas from internal combustion engine - Google Patents
Catalyst for cleaning exhaust gas from internal combustion engineInfo
- Publication number
- JPH08257407A JPH08257407A JP7067611A JP6761195A JPH08257407A JP H08257407 A JPH08257407 A JP H08257407A JP 7067611 A JP7067611 A JP 7067611A JP 6761195 A JP6761195 A JP 6761195A JP H08257407 A JPH08257407 A JP H08257407A
- Authority
- JP
- Japan
- Prior art keywords
- catalyst
- exhaust gas
- mesopores
- noble metal
- silicate
- 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 77
- 238000002485 combustion reaction Methods 0.000 title claims description 24
- 238000004140 cleaning Methods 0.000 title 1
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 37
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims abstract description 27
- 238000000746 purification Methods 0.000 claims description 20
- 229910052697 platinum Inorganic materials 0.000 claims description 11
- 229910052703 rhodium Inorganic materials 0.000 claims description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 9
- 239000001301 oxygen Substances 0.000 abstract description 9
- 229910052760 oxygen Inorganic materials 0.000 abstract description 9
- 238000006555 catalytic reaction Methods 0.000 abstract description 3
- 238000006243 chemical reaction Methods 0.000 abstract description 3
- 230000001404 mediated effect Effects 0.000 abstract description 2
- 238000000151 deposition Methods 0.000 abstract 1
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 63
- 239000007789 gas Substances 0.000 description 34
- 239000010948 rhodium Substances 0.000 description 27
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 23
- 239000010457 zeolite Substances 0.000 description 22
- 229910021536 Zeolite Inorganic materials 0.000 description 21
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 21
- 239000011148 porous material Substances 0.000 description 16
- 238000005245 sintering Methods 0.000 description 14
- 239000000843 powder Substances 0.000 description 12
- 239000010970 precious metal Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 9
- 230000004913 activation Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 230000003197 catalytic effect Effects 0.000 description 6
- 238000011156 evaluation Methods 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 239000008119 colloidal silica Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 238000001027 hydrothermal synthesis Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- FVMNIZVEFVZGKW-UHFFFAOYSA-N [O-][N+]([O-])=O.[Pt+2] Chemical compound [O-][N+]([O-])=O.[Pt+2] FVMNIZVEFVZGKW-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 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
- 238000002474 experimental method Methods 0.000 description 1
- 239000012013 faujasite Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910052680 mordenite Inorganic materials 0.000 description 1
- 150000007530 organic bases Chemical class 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000002360 preparation method Methods 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
- 239000012266 salt solution Substances 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
Landscapes
- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は内燃機関の排気ガス浄化
用触媒に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst for an internal combustion engine.
【０００２】[0002]
【従来の技術】内燃機関の排気ガスを浄化するためにそ
の排気通路に触媒を設けることは一般に行なわれてい
る。従来の三元触媒ではアルミナに貴金属が担持されて
いるが、最近はゼオライトに貴金属を担持させてなる触
媒が注目されている。ゼオライトは排気ガス中のＨＣを
吸着する性質があり、該ＨＣの燃焼浄化に有利であるた
めであり、また、該ゼオライトに貴金属が担持されてい
ると、排気ガス中のＮＯｘの吸着にも効果があり、該Ｎ
Ｏｘの分解浄化に有利になるからである。2. Description of the Related Art It is common practice to provide a catalyst in the exhaust passage of an internal combustion engine in order to purify the exhaust gas. In conventional three-way catalysts, noble metal is supported on alumina, but recently, a catalyst in which noble metal is supported on zeolite has attracted attention. This is because zeolite has a property of adsorbing HC in exhaust gas and is advantageous for combustion purification of HC, and when a precious metal is supported on the zeolite, it is also effective for adsorbing NOx in exhaust gas. And the N
This is because it is advantageous for the decomposition and purification of Ox.
【０００３】しかし、従来のゼオライトに担持させた貴
金属は、高温に長時間さらされるとシンタリングを起し
触媒活性が大きく低下する、という問題がある。However, the conventional noble metal supported on zeolite has a problem that if it is exposed to high temperature for a long time, sintering occurs and the catalytic activity is greatly reduced.
【０００４】この問題に対して、ゼオライトの細孔に該
ゼオライトの骨格を形成しない多価金属酸化物を取り込
んでなる担体に貴金属を担持させる、という提案がある
（特開平４−２２２６３２号公報参照）。この提案は、
上記多価金属酸化物によって貴金属のシンタリングを防
止しようとするものである。To solve this problem, there is a proposal that a noble metal is supported on a carrier in which the polyvalent metal oxide that does not form the skeleton of the zeolite is incorporated into the pores of the zeolite (see JP-A-4-222632). ). This proposal is
The polyvalent metal oxide is intended to prevent sintering of precious metals.
【０００５】[0005]
【発明が解決しようとする課題】本発明の課題は、貴金
属の高温でのシンタリングを防止しながら、当該触媒の
活性温度域を高温側にシフトさせることにあり、より具
体的なレベルでいえば、理論空燃比よりも酸素過剰な所
謂リーン雰囲気において排気ガスが高温になっても、該
排気ガス中のＮＯｘ（窒素酸化物）を効率良く浄化する
ことができるようにすることにある。An object of the present invention is to shift the active temperature range of the catalyst to the high temperature side while preventing sintering of the noble metal at high temperature, and can be said at a more specific level. For example, even if the exhaust gas has a high temperature in a so-called lean atmosphere in which oxygen is more than the stoichiometric air-fuel ratio, NOx (nitrogen oxide) in the exhaust gas can be efficiently purified.
【０００６】すなわち、本発明者がゼオライトにおける
貴金属のシンタリング現象について種々の実験・検討を
行なった結果、この現象は貴金属が主としてゼオライト
の表面に担持されているためである、という知見を得
た。That is, as a result of various experiments and studies on the sintering phenomenon of noble metal in zeolite by the present inventor, it was found that this phenomenon is mainly because the noble metal is supported on the surface of zeolite. .
【０００７】具体的に説明すると、ゼオライトの細孔径
は小さいものでは０．３ｎｍ程度、大きいものでも０．
８ｎｍ程度である。この細孔径であれば理論的には細孔
内に貴金属を取り込むことができるが、実際には貴金属
はゼオライトの表面に主として担持され、細孔内に取り
込まれている貴金属量は少ない。このことは貴金属担持
ゼオライトを高温にさらすと、ゼオライトの結晶構造自
体は壊れていないのにその触媒活性が大きく低下するこ
とからわかる。つまり、ゼオライトの表面に分散担持さ
れている貴金属同士は立体障害がないから、比較的簡単
にシンタリングを起し、触媒活性が低下するものであ
る。More specifically, zeolite having a small pore diameter is about 0.3 nm, and zeolite having a large pore diameter is about 0.3 nm.
It is about 8 nm. With this pore size, the noble metal can theoretically be taken into the pores, but in reality, the noble metal is mainly supported on the surface of the zeolite, and the amount of the noble metal taken into the pores is small. This can be seen from the fact that when the precious metal-supported zeolite is exposed to high temperatures, the catalytic activity of the zeolite is greatly reduced although the crystal structure of the zeolite itself is not broken. That is, since the precious metals dispersedly supported on the surface of the zeolite have no steric hindrance, the sintering is relatively easy to occur and the catalytic activity is lowered.
【０００８】一方、ゼオライトの表面に担持されている
貴金属は、内燃機関がリーン空燃比で運転されると、酸
素が過剰な排気ガスにさらされることになる。このた
め、当該触媒の場合は、この過剰な酸素によって排気ガ
ス中のＨＣ（炭化水素）やＣＯ（一酸化炭素）の燃焼反
応が進み易くなり、比較的低い温度で触媒活性が発現す
ることになる。On the other hand, the noble metal carried on the surface of zeolite is exposed to excess exhaust gas of oxygen when the internal combustion engine is operated at a lean air-fuel ratio. Therefore, in the case of the catalyst, the excess oxygen facilitates the combustion reaction of HC (hydrocarbon) and CO (carbon monoxide) in the exhaust gas, and the catalytic activity is expressed at a relatively low temperature. Become.
【０００９】しかし、触媒の活性温度域が低いというこ
とは、内燃機関が高速で連続運転されると、排気ガス温
度が高くなるために該排気ガスの所期の浄化が望めなく
なることを意味する。もちろん、この問題に対しては、
触媒の活性温度域が高い触媒金属を選択して使用するこ
とが考えられるのであるが、仮にそのような触媒金属を
採用して、上記シンタリングの問題があるために、触媒
が早期に劣化し、必ずしも好結果を得ることができな
い。However, the low catalyst activation temperature range means that when the internal combustion engine is continuously operated at high speed, the exhaust gas temperature becomes high, and the desired purification of the exhaust gas cannot be expected. . Of course, for this problem,
It is conceivable to select and use a catalyst metal with a high catalyst activation temperature range.However, if such a catalyst metal is adopted and the above-mentioned sintering problem occurs, the catalyst will deteriorate early. , Not always good results.
【００１０】なお、上記従来技術の公報には、大孔径の
ゼオライトの代表としてＹ型ゼオライトが記載されてい
るが、このものでもその細孔径は最大０．７４ｎｍ程度
である。The above-mentioned prior art publication describes Y-type zeolite as a representative of large-pore zeolites, but even in this case, the maximum pore size is about 0.74 nm.
【００１１】[0011]
【課題を解決するための手段及びその作用】そこで、本
発明においては、ゼオライトのような結晶質のシリケー
トを貴金属の担体として採用するにあたり、該シリケー
トの孔径を一般のゼオライトの細孔径の数倍乃至数十倍
の大きさにすることによって、貴金属のシンタリングを
防止するとともに、当該触媒の活性温度域を従来のゼオ
ライトを用いた触媒よりも高温側にシフトさせるように
したものである。以下、特許請求の範囲の各請求項に係
る発明について具体的に説明する。Therefore, in the present invention, in adopting a crystalline silicate such as zeolite as a carrier of a noble metal, the pore size of the silicate is several times larger than that of general zeolite. By making the size to several tens of times, sintering of noble metal is prevented and the active temperature range of the catalyst is shifted to a higher temperature side than that of the catalyst using the conventional zeolite. Hereinafter, the invention according to each claim of the claims will be specifically described.
【００１２】＜請求項１に係る発明＞請求項１に係る発
明は、担体に貴金属を担持させてなる内燃機関の排気ガ
ス浄化用触媒であって、上記担体がメゾポアを有する結
晶質のシリケートであり、上記貴金属の一部が該シリケ
ートのメゾポア内に担持されていることを特徴とするも
のである。<Invention of Claim 1> The invention of claim 1 is a catalyst for purifying exhaust gas of an internal combustion engine, comprising a carrier carrying a noble metal, wherein the carrier is a crystalline silicate having mesopores. It is characterized in that a part of the noble metal is carried in the mesopores of the silicate.
【００１３】当該発明の場合、担体である結晶質のシリ
ケートがメゾポア（径１〜２５ｎｍの中間細孔）を有す
るから、触媒成分としての貴金属を担持させる際に該貴
金属がメゾポア内に容易に入り込む。このため、シリケ
ートの表面だけでなく、各メゾポアの内面にも貴金属が
表面と同様に多く担持される。一方、このようなメゾポ
アは、シリケート表面に比べて酸素濃度が低くなる。従
って、当該メゾポア内では、酸素を仲立ちとする貴金属
の触媒反応がシリケート表面に比べて進み難くなり、よ
り高温にならないと当該触媒反応が進まなくなる。よっ
て、触媒全体としてみた場合にその活性温度域が高温側
にずれることになる。In the case of the present invention, since the crystalline silicate as a carrier has mesopores (medium pores having a diameter of 1 to 25 nm), the precious metal easily enters the mesopores when supporting the precious metal as a catalyst component. . Therefore, not only the surface of the silicate but also the inner surface of each mesopore is loaded with a large amount of noble metal as well as the surface. On the other hand, such mesopores have a lower oxygen concentration than the silicate surface. Therefore, in the mesopore, the catalytic reaction of the noble metal mediated by oxygen becomes difficult to proceed as compared with the silicate surface, and the catalytic reaction does not proceed unless the temperature becomes higher. Therefore, when viewed as the whole catalyst, the activation temperature range shifts to the high temperature side.
【００１４】また、上述の如く各メゾポア内に担持され
た貴金属は、相隣るメゾポア間の孔壁がその移動の立体
障害となる。従って、当該触媒が高温にさらされた場合
でも、異なるメゾポアの貴金属同士がシンタリングを起
すことが少なくなる。Further, as described above, in the noble metal supported in each mesopore, the pore wall between adjacent mesopores becomes a steric hindrance of the movement. Therefore, even when the catalyst is exposed to high temperatures, sintering of rare metals of different mesopores is less likely to occur.
【００１５】ここに、上記結晶質のシリケートとして
は、オルトケイ酸塩であっても、メタケイ酸塩であって
も、あるいはゼオライトのような各種の縮合ケイ酸塩で
あってもよい。また、該シリケートに担持させる貴金属
としては、Ｐｔを始めとして、Ｒｈ、Ｉｒ、Ｐｄなどを
採用することができ、その種類は特に問わない。The crystalline silicate may be orthosilicate, metasilicate, or various condensed silicates such as zeolite. As the noble metal supported on the silicate, Ph, Rh, Ir, Pd, etc. can be adopted, and the kind thereof is not particularly limited.
【００１６】＜請求項２に係る発明＞この発明は、上記
請求項１に記載されている内燃機関の排気ガス浄化用触
媒において、上記メゾポアの孔径を２〜２０ｎｍとした
ことを特徴とする。<Invention of Claim 2> The present invention is characterized in that in the exhaust gas purifying catalyst for an internal combustion engine described in claim 1, the mesopore has a pore diameter of 2 to 20 nm.
【００１７】メゾポア径が２ｎｍ未満であれば、該ポア
内に貴金属が入り難くなる。一方、メゾポア径が２０ｎ
ｍよりも大きくなると、排気ガスが通り抜け易くなって
反応場の形成が困難になる。また、分子径が比較的大き
い酸素も該メゾポア内に容易に入ることになって活性温
度域の高温側へのシフト効果が低くなり、さらに、貴金
属の移動が容易になってシンタリング防止に不利にな
る。When the mesopore diameter is less than 2 nm, it becomes difficult for precious metal to enter the pores. On the other hand, the mesopore diameter is 20n
If it is larger than m, the exhaust gas is likely to pass through and it becomes difficult to form a reaction field. Oxygen having a relatively large molecular diameter easily enters the mesopores, reducing the effect of shifting the active temperature region to the high temperature side, and further facilitating the movement of noble metals, which is disadvantageous in preventing sintering. become.
【００１８】＜請求項３に係る発明＞この発明は、上記
請求項１に記載されている内燃機関の排気ガス浄化用触
媒において、上記メゾポア径を２〜１６ｎｍとしたこと
を特徴とする。<Invention of Claim 3> The present invention is characterized in that, in the exhaust gas purifying catalyst for an internal combustion engine described in claim 1, the mesopore diameter is 2 to 16 nm.
【００１９】メゾポア径がこのような範囲であれば、該
メゾポア内への貴金属の担持、高温側への活性温度域の
シフト、触媒浄化性能の向上、貴金属のシンタリング防
止により有利になる。When the mesopore diameter is in such a range, it is advantageous in supporting the precious metal in the mesopore, shifting the activation temperature range to the high temperature side, improving catalyst purifying performance, and preventing sintering of the precious metal.
【００２０】＜請求項４に係る発明＞この発明は、上記
請求項１乃至請求項３のいずれか一に記載されている内
燃機関の排気ガス浄化用触媒において、上記貴金属をＰ
ｔ及びＲｈとしたことを特徴とする。<Invention of Claim 4> The present invention is the exhaust gas purifying catalyst for an internal combustion engine according to any one of claims 1 to 3, wherein the precious metal is P
t and Rh.
【００２１】貴金属をＰｔとＲｈにするのは、前者は排
気ガス中のＨＣの燃焼に好適であり、後者は排気ガス中
のＮＯｘの吸着に好適であるためであり、リーン雰囲気
においてＨＣを燃焼させながらＮＯｘを分解浄化するこ
とができる。The reason why the noble metals are Pt and Rh is that the former is suitable for the combustion of HC in the exhaust gas and the latter is suitable for the adsorption of NOx in the exhaust gas, and the HC is burned in the lean atmosphere. While doing so, NOx can be decomposed and purified.
【００２２】＜請求項５に係る発明＞この発明は、上記
請求項４に記載されている内燃機関の排気ガス浄化用触
媒において、上記ＰｔとＲｈとの重量比をＲｈ／Ｐｔ＝
０．０１〜１としたことを特徴とするものである。<Invention of Claim 5> According to the present invention, in the catalyst for purifying exhaust gas of an internal combustion engine according to claim 4, the weight ratio of Pt to Rh is Rh / Pt =
It is characterized by being set to 0.01 to 1.
【００２３】このようなＰｔ／Ｒｈ比であれば、ＨＣを
燃焼させながらＮＯｘを分解させる上でより有利にな
る。すなわち、Ｒｈは微量添加で効果があり、多く加え
ても効果はなく、多量になるとむしろ耐久性低下の原因
となる。このために、本発明ではＲｈ／Ｐｔ比の上限を
１としているものである。もっとも、Ｒｈ量が少なすぎ
ると、該Ｒｈ添加の効果が明瞭に現われず、そのために
上記Ｒｈ／Ｐｔ比の下限を０．０１としているものであ
る。Such a Pt / Rh ratio is more advantageous for decomposing NOx while burning HC. That is, adding a small amount of Rh has an effect, and adding a large amount of Rh has no effect, and a large amount of Rh causes deterioration of durability. Therefore, in the present invention, the upper limit of the Rh / Pt ratio is 1. However, if the amount of Rh is too small, the effect of the addition of Rh does not clearly appear, and therefore the lower limit of the Rh / Pt ratio is 0.01.
【００２４】[0024]
【発明の効果】請求項１に係る発明によれば、メゾポア
を有する結晶質のシリケートを担体とし、該シリケート
のメゾポア内にも貴金属を担持させたから、触媒の活性
温度域を高温側にずらして排気ガス温度が高いときの排
気ガス浄化率を高めることができるとともに、貴金属の
シンタリングを防止して当該触媒の耐熱性を高めること
ができる。According to the invention of claim 1, since the crystalline silicate having mesopores is used as a carrier and the noble metal is also loaded in the mesopores of the silicate, the active temperature range of the catalyst is shifted to the high temperature side. It is possible to increase the exhaust gas purification rate when the exhaust gas temperature is high, and prevent the sintering of precious metals to improve the heat resistance of the catalyst.
【００２５】請求項２に係る発明によれば、上記請求項
１に記載されている内燃機関の排気ガス浄化用触媒にお
いて、上記メゾポアの孔径を２〜２０ｎｍとしたから、
メゾポア内に貴金属を担持させ、触媒の活性温度域を高
めて排気ガス浄化率を向上させるとともに、貴金属のシ
ンタリングを防止する上で有利になる。According to the invention of claim 2, in the exhaust gas purifying catalyst for an internal combustion engine according to claim 1, the mesopore has a pore diameter of 2 to 20 nm.
It is advantageous in that the noble metal is supported in the mesopores, the active temperature range of the catalyst is increased to improve the exhaust gas purification rate, and the sintering of the noble metal is prevented.
【００２６】請求項３に係る発明によれば、上記請求項
１に記載されている内燃機関の排気ガス浄化用触媒にお
いて、上記メゾポア径を２〜１６ｎｍとしたから、触媒
の活性温度域を高めて排気ガス浄化率を向上させなが
ら、貴金属のシンタリングを防止する上でさらに有利に
なる。According to the invention of claim 3, in the exhaust gas purifying catalyst for an internal combustion engine according to claim 1, the mesopore diameter is set to 2 to 16 nm, so that the active temperature range of the catalyst is increased. Therefore, it becomes more advantageous in preventing sintering of precious metals while improving the exhaust gas purification rate.
【００２７】請求項４に係る発明によれば、上記請求項
１乃至請求項３のいずれか一に記載されている内燃機関
の排気ガス浄化用触媒において、上記貴金属をＰｔ及び
Ｒｈとしたから、リーン雰囲気においてＨＣを燃焼させ
ながらＮＯｘを分解浄化することができる。According to the invention of claim 4, in the exhaust gas purifying catalyst for an internal combustion engine according to any one of claims 1 to 3, the noble metals are Pt and Rh. NOx can be decomposed and purified while burning HC in a lean atmosphere.
【００２８】請求項５に係る発明によれば、上記請求項
４に記載されている内燃機関の排気ガス浄化用触媒にお
いて、上記ＰｔとＲｈとの重量比をＲｈ／Ｐｔ＝０．０
１〜１としたから、リーン雰囲気においてＨＣを燃焼さ
せながらＮＯｘを分解させる上でさらに有利になる。According to the invention of claim 5, in the exhaust gas purifying catalyst for an internal combustion engine according to claim 4, the weight ratio of Pt to Rh is Rh / Pt = 0.0.
Since it is set to 1 to 1, it is further advantageous in decomposing NOx while burning HC in a lean atmosphere.
【００２９】[0029]
【実施例】以下、本発明の実施例を説明する。Embodiments of the present invention will be described below.
【００３０】＜触媒の構造＞図１には本発明の排気ガス
浄化用触媒１が示されている。該触媒１において、２は
耐熱性を有する結晶質のシリケートであり、多数のメゾ
ポア３を有する。そして、このシリケート２にはその表
面だけでなく、メゾポア３の内面にも触媒成分としての
貴金属４が担持されている。従って、各メゾポア３の貴
金属４は孔壁５によって隔てられている。<Structure of Catalyst> FIG. 1 shows an exhaust gas purifying catalyst 1 of the present invention. In the catalyst 1, 2 is a heat-resistant crystalline silicate and has a large number of mesopores 3. The silicate 2 carries the precious metal 4 as a catalyst component not only on its surface but also on the inner surface of the mesopore 3. Therefore, the noble metal 4 of each mesopore 3 is separated by the hole wall 5.
【００３１】＜触媒の調製＞ −本発明例− 水熱合成法によってメゾポアを有するメゾポアシリケー
ト粉末（ＳｉＯ2 のポーラス材料であり、ＮａＨＳｉ2
Ｏ5 ，Ｓｉ2 Ｏ5 で表わすことができる）を合成した。
該メゾポアシリケートのメゾポア径の調整は、有機塩基
をテンプレート（鋳型）として用いることによって行な
った。<Catalyst Preparation> -Invention Example-Mesoposilicate powder having mesopores by hydrothermal synthesis method (a porous material of SiO 2 , NaHSi 2
O 5 , Si 2 O 5 ) can be synthesized.
The adjustment of the mesopore diameter of the mesopore silicate was carried out by using an organic base as a template.
【００３２】すなわち、コロイダルシリカとテトラジシ
ルトリメチルアンモニウムブロミド（鋳型材）とイオン
交換水とを混合し、室温で充分に（３時間）撹拌する。
このとき、ＮａＯＨを添加しｐＨが９〜１１となるよう
に調整する。こうして得られた溶液をオートクレーブに
入れ、１２０℃に加熱した状態を１４〜２０時間保持す
る。この処理によってメゾポアシリケートが合成される
ので、遠心分離によって溶媒と粉末（メゾポアシリケー
ト）とを分離した後、イオン交換水で充分に洗浄する。
そして、得られた粉末を４００℃で焼成することによっ
て、目的とするメゾポアシリケートを得る。なお、必要
とするメゾポア径の大きさによって上記コロイダルシリ
カに加える鋳型材の種類と量、さらには水熱合成の条件
を変えることになる。That is, colloidal silica, tetradicyltrimethylammonium bromide (template material) and ion-exchanged water are mixed and sufficiently stirred at room temperature (3 hours).
At this time, NaOH is added to adjust the pH to 9-11. The solution thus obtained is placed in an autoclave, and the state of being heated to 120 ° C. is maintained for 14 to 20 hours. Since mesopoacylate is synthesized by this treatment, the solvent and the powder (mesopoacysilicate) are separated by centrifugation and then thoroughly washed with ion-exchanged water.
Then, the obtained powder is fired at 400 ° C. to obtain the desired mesopoacylate. The type and amount of the template material added to the colloidal silica and the conditions for hydrothermal synthesis will be changed depending on the required mesopore diameter.
【００３３】次に硝酸白金−Ｐソルト溶液（ジニトロジ
アミン白金(II)硝酸酸性水溶液）と硝酸ロジウム水溶液
とを混合し、該混合水溶液と上記メゾポアシリケート粉
末とを混合し、スプレードライ法によって該メゾポアシ
リケート粉末にＰｔとＲｈとを担持させた。そうして、
得られた触媒粉末を直径１inch（インチ）のコア形状の
コージェライト製ハニカム状モノリス担体にウォッシュ
コートすることによって、目的とする排気ガス浄化用触
媒を得た。Next, a platinum nitrate-P salt solution (dinitrodiamine platinum (II) nitric acid acidic aqueous solution) and a rhodium nitrate aqueous solution are mixed, and the mixed aqueous solution is mixed with the mesopoacylicate powder, and the mixture is spray-dried. Pt and Rh were supported on the mesoposilicate powder. And then
The obtained catalyst powder was wash-coated on a core-shaped cordierite honeycomb monolith carrier having a diameter of 1 inch (inch) to obtain a target exhaust gas purifying catalyst.
【００３４】上記排気ガス浄化用触媒において、モノリ
ス担体は４００セル／inch2 のものであり、ウォッシュ
コート量はハニカム担体の３０ｗｔ％とし、ＰｔとＲｈ
とを合わせた量は４．５ｇ／Ｌ（ハニカム担体１Ｌ当た
り４．５ｇ）、その比がＰｔ／Ｒｈ＝７５／１となるよ
うにした。In the above exhaust gas purifying catalyst, the monolith carrier is 400 cells / inch 2 , the washcoat amount is 30 wt% of the honeycomb carrier, and Pt and Rh are
The total amount was 4.5 g / L (4.5 g per 1 L of honeycomb carrier), and the ratio was Pt / Rh = 75/1.
【００３５】−比較例− アルミナ、ＭＦＩ（ＺＳＭ−５）、モルデナイト及びＦ
ＡＵ（フォージャサイト）の各粉末を準備し、これらに
上記本発明例と同様にしてＰｔ及びＲｈを担持させ、得
られた触媒粉末を同様のモノリス担体にウォッシュコー
トによって担持させた。ウォッシュコート量並びにＰ
ｔ，Ｒｈの量と比については本発明例と同じにした。-Comparative Example- Alumina, MFI (ZSM-5), mordenite and F
Powders of AU (faujasite) were prepared, Pt and Rh were loaded on these powders in the same manner as in the above-mentioned example of the present invention, and the obtained catalyst powders were loaded on the same monolith carrier by washcoating. Wash coat amount and P
The amounts and ratios of t and Rh were the same as in the present invention.
【００３６】＜触媒の評価＞ −比表面積について− 上記本発明例及び比較例の各触媒粉末について、そのフ
レッシュ時（未使用時）の比表面積と、熱処理（触媒に
大気中において９００℃×５０時間の熱処理を施した）
後の比表面積を測定したところ、図２に示す結果が得ら
れた。<Evaluation of catalyst> -Regarding specific surface area-For each of the catalyst powders of the present invention and the comparative example, a specific surface area of the catalyst powder when fresh (unused) and heat treatment (catalyst in air at 900 ° C. × 50) Heat treated for hours)
When the subsequent specific surface area was measured, the results shown in FIG. 2 were obtained.
【００３７】同図から、メゾポアシリケートを用いた本
発明触媒は、他の触媒に比べて比表面積が大きく触媒と
して有利であること、熱処理による比表面積の低下が少
ないから耐熱性に優れていることがわかる。From the figure, the catalyst of the present invention using mesopoacylate has a large specific surface area as compared with other catalysts and is advantageous as a catalyst, and since the specific surface area is less decreased by heat treatment, it is excellent in heat resistance. I understand.
【００３８】本発明触媒の比表面積が比較例のそれより
も大きいのは、比較例の場合は貴金属（Ｐｔ及びＲｒ）
によってその細孔が塞がれているのに対し、本発明触媒
の場合は、そのメゾポアがほとんど閉塞されていないた
めであると考えられる。また、本発明例触媒の耐熱性が
高いのは、各メゾポア内に担持されている貴金属のシン
タリングをほとんど生じないためであると考えられる。The specific surface area of the catalyst of the present invention is larger than that of the comparative example because noble metals (Pt and Rr) are present in the comparative example.
It is considered that, while the pores are blocked by the above, in the case of the catalyst of the present invention, the mesopores are hardly blocked. Further, it is considered that the catalyst of the present invention has high heat resistance because sintering of the noble metal supported in each mesopore hardly occurs.
【００３９】−触媒活性及び活性温度域について− 上記メゾポアシリケート（メゾポア径８ｎｍ）を用いた
本発明触媒と、上記ＭＦＩを用いた比較例の触媒（Ｐ
ｔ，Ｒｈ／ＭＦＩ）とについて、固定床流通式反応評価
装置を用いてＮＯｘ浄化率の温度特性を同じ条件で調べ
た。-Regarding catalytic activity and active temperature range-The catalyst of the present invention using the above mesopoacylate (mesopore diameter 8 nm) and the catalyst of the comparative example using the above MFI (P
t, Rh / MFI), the temperature characteristics of the NOx purification rate were examined under the same conditions using a fixed bed flow reaction evaluation apparatus.
【００４０】すなわち、上記モノリス担体に触媒粉末を
ウォッシュコートしてなる各触媒を上記評価装置に取付
け、ヒータで予熱した評価ガスを該触媒に通しＮＯｘ浄
化率を調べた。評価ガス組成は次の通りであり、ガス速
度はＳＶ＝５５０００ｈｒ-1とした。結果は図３に示さ
れている。That is, each catalyst obtained by wash-coating the above monolith carrier with catalyst powder was attached to the above evaluation apparatus, and the evaluation gas preheated by a heater was passed through the catalyst to examine the NOx purification rate. The composition of the evaluation gas is as follows, and the gas velocity was SV = 55000 hr −1 . The results are shown in Figure 3.
【００４１】（評価ガス組成） ＨＣ；４０００ｐｐｍＣ，ＮＯｘ；２５０ｐｐｍ，Ｃ
Ｏ；０．１５％，Ｈ2 ；６５０ｐｐｍ，Ｏ2 ；７％，Ｃ
Ｏ2 ；１０％，残部Ｎ2 (Evaluation gas composition) HC: 4000 ppm C, NOx: 250 ppm, C
O; 0.15%, H 2 ; 650 ppm, O 2 ; 7%, C
O 2 ; 10%, balance N 2
【００４２】図３によれば、本発明触媒と比較例とで
は、ＮＯｘ浄化率のピーク値自体には大差がないもの
の、本発明触媒の場合は、活性温度域が比較例のものよ
りも高温側に数十度ずれている。これは、本発明触媒で
はメゾポア内の酸素濃度が比較例のものよりも低く、よ
り高温にならないと触媒活性を発現しない結果であると
考えられる。According to FIG. 3, there is no great difference in the peak value of the NOx purification rate between the catalyst of the present invention and the comparative example, but in the case of the catalyst of the present invention, the activation temperature range is higher than that of the comparative example. It is shifted to the side by several tens of degrees. This is considered to be because the oxygen concentration in the mesopores of the catalyst of the present invention is lower than that of the comparative example, and the catalytic activity is not expressed unless the temperature becomes higher.
【００４３】−メゾポア径とＮＯｘ浄化率・活性温度域
のシフト量との関係− 上記本発明触媒について、そのメゾポアシリケートのメ
ゾポア径が異なるものを調製し、メゾポア径がＮＯｘ浄
化率及び活性温度域の高温側へのシフト量に及ぼす影響
を調べた。結果は図４に示されている。-Relationship between mesopore diameter and NOx purification rate / shift amount in active temperature range-The catalysts of the present invention having different mesopore diameters of the mesopore silicate were prepared, and the mesopore diameter was the NOx purification rate and the activation temperature. The effect on the amount of shift to the high temperature side of the region was investigated. The results are shown in Figure 4.
【００４４】同図によれば、ＮＯｘ浄化率と活性温度域
の高温側へのシフト量とは、メゾポア径の変化に関して
略同様の傾向を示している。すなわち、メゾポア径８ｎ
ｍ前後でＮＯｘ浄化率及び活性温度域の高温側へのシフ
ト量は最も高い値を示し、それよりもメゾポア径が大き
くなる場合も小さくなる場合もそれらの値は低下してい
っている。According to the figure, the NOx purification rate and the shift amount of the active temperature region to the high temperature side show substantially the same tendency with respect to the change of the mesopore diameter. That is, mesopore diameter 8n
The NOx purification rate and the amount of shift of the activation temperature range to the high temperature side show the highest values around m, and those values are decreasing when the mesopore diameter becomes larger or smaller than that.
【００４５】同図の結果から、メゾポア径が２〜２０ｎ
ｍの範囲にあれば、所期の効果を得ることができるこ
と、２〜１６ｎｍの範囲が良いこと、特に４０〜１２０
ｎｍの範囲が良いことがわかる。From the results shown in the figure, the mesopore diameter is 2 to 20n.
If it is in the range of m, the desired effect can be obtained, and the range of 2 to 16 nm is good, especially 40 to 120
It can be seen that the nm range is good.
【００４６】−ＰｔとＲｈとの重量比について− 担体として上記メゾポアシリケート（メゾポア径８ｎ
ｍ）を用い、貴金属活性種としてのＰｔとＲｈとの成分
比（重量比）を種々に変えた触媒を調製した。これらの
触媒ではＰｔとＲｈとの総量は３ｇ／Ｌとなるようにし
た。モノリス担体は４００セル／inch2 のハニカムであ
り、ウォッシュコート量はハニカム担体の３５ｗｔ％と
した。これらの触媒の比表面積には大きな違いはない。
そこで、これらの触媒について、大気中で９００℃×５
０時間の加熱処理を施した後、ＮＯｘ浄化率を測定し
た。結果は図５に示されている。-Regarding the weight ratio of Pt and Rh- As the carrier, the above-mentioned mesopore silicate (mesopore diameter 8n).
m) was used to prepare catalysts in which the component ratio (weight ratio) of Pt and Rh as active species of noble metal was variously changed. In these catalysts, the total amount of Pt and Rh was set to 3 g / L. The monolith carrier was a honeycomb of 400 cells / inch 2 , and the washcoat amount was 35 wt% of the honeycomb carrier. There is no significant difference in the specific surface area of these catalysts.
Therefore, for these catalysts, 900 ° C x 5 in air
After performing the heat treatment for 0 hour, the NOx purification rate was measured. Results are shown in FIG.
【００４７】同図によれば、上記ＰｔとＲｈとの重量比
がＲｈ／Ｐｔ＝０．０１〜１において高いＮＯｘ浄化率
が得られること、Ｒｈ／Ｐｔ＝０．０１〜０．２がより
好ましいことがわかる。According to the figure, when the weight ratio of Pt and Rh is Rh / Pt = 0.01 to 1, a high NOx purification rate is obtained, and Rh / Pt = 0.01 to 0.2 is more preferable. It turns out to be preferable.
【図１】本発明の触媒構造の概略を示す断面図FIG. 1 is a sectional view showing an outline of a catalyst structure of the present invention.
【図２】本発明例及び比較例の各触媒についてフレッシ
ュ時と熱処理後のＢＥＴ比表面積を比較したグラフ図FIG. 2 is a graph diagram comparing the BET specific surface areas of each catalyst of the present invention example and comparative example during fresh and after heat treatment.
【図３】本発明触媒（メゾポアシリケート担体）及び比
較例触媒（ＭＦＩ担体）のＮＯｘ浄化率の温度特性を示
すグラフ図FIG. 3 is a graph showing the temperature characteristics of the NOx purification rate of the catalyst of the present invention (mesopoacylate carrier) and the comparative catalyst (MFI carrier).
【図４】メゾポア径とＮＯｘ浄化率・活性温度域のシフ
ト量との関係を示すグラフ図FIG. 4 is a graph showing the relationship between mesopore diameter and NOx purification rate / shift amount in active temperature range.
【図５】Ｐｔ／Ｒｈ比がＮＯｘ浄化率に及ぼす影響を示
すグラフ図FIG. 5 is a graph showing the effect of the Pt / Rh ratio on the NOx purification rate.
１ 排気ガス浄化用触媒 ２ メゾポアシリケート ３ メゾポア ４ 貴金属 ５ 孔壁 1 Exhaust Gas Purification Catalyst 2 Mesoposilicate 3 Mesopore 4 Precious Metal 5 Hole Wall
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｂ０１Ｊ 23/46 ３１１ Ｆ０１Ｎ 3/28 ３０１Ｐ Ｆ０１Ｎ 3/28 ＺＡＢ Ｂ０１Ｄ 53/36 ＺＡＢ ３０１ １０２Ｂ １０２Ｈ ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical display location B01J 23/46 311 F01N 3/28 301P F01N 3/28 ZAB B01D 53/36 ZAB 301 102B 102H
Claims (5)
の排気ガス浄化用触媒において、 上記担体がメゾポアを有する結晶質のシリケートであ
り、上記貴金属の一部が該シリケートのメゾポア内に担
持されていることを特徴とする内燃機関の排気ガス浄化
用触媒。1. A catalyst for purifying exhaust gas of an internal combustion engine, comprising a carrier carrying a noble metal, wherein the carrier is a crystalline silicate having mesopores, and a part of the noble metal is carried in the mesopores of the silicate. An exhaust gas purifying catalyst for an internal combustion engine.
気ガス浄化用触媒において、 上記メゾポア径が２〜２０ｎｍであることを特徴とする
内燃機関の排気ガス浄化用触媒。2. The exhaust gas purifying catalyst for an internal combustion engine according to claim 1, wherein the mesopore diameter is 2 to 20 nm.
気ガス浄化用触媒において、 上記メゾポア径が２〜１６ｎｍであることを特徴とする
内燃機関の排気ガス浄化用触媒。3. The exhaust gas purifying catalyst for an internal combustion engine according to claim 1, wherein the mesopore diameter is 2 to 16 nm.
載されている内燃機関の排気ガス浄化用触媒において、 上記貴金属がＰｔとＲｈであることを特徴とする内燃機
関の排気ガス浄化用触媒。4. The exhaust gas purification catalyst for an internal combustion engine according to any one of claims 1 to 3, wherein the noble metals are Pt and Rh. Catalyst.
気ガス浄化用触媒において、 上記ＰｔとＲｈとの重量比がＲｈ／Ｐｔ＝０．０１〜１
であることを特徴とする内燃機関の排気ガス浄化用触
媒。5. The exhaust gas purifying catalyst for an internal combustion engine according to claim 4, wherein the weight ratio of Pt to Rh is Rh / Pt = 0.01 to 1.
A catalyst for purifying exhaust gas of an internal combustion engine, characterized in that
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06761195A JP3794035B2 (en) | 1995-03-27 | 1995-03-27 | Catalyst for exhaust gas purification of internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06761195A JP3794035B2 (en) | 1995-03-27 | 1995-03-27 | Catalyst for exhaust gas purification of internal combustion engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08257407A true JPH08257407A (en) | 1996-10-08 |
| JP3794035B2 JP3794035B2 (en) | 2006-07-05 |
Family
ID=13349927
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06761195A Expired - Fee Related JP3794035B2 (en) | 1995-03-27 | 1995-03-27 | Catalyst for exhaust gas purification of internal combustion engine |
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| Country | Link |
|---|---|
| JP (1) | JP3794035B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006297348A (en) * | 2005-04-25 | 2006-11-02 | Asahi Kasei Corp | Catalyst for clarifying exhaust gas |
| US7223716B1 (en) | 1999-04-09 | 2007-05-29 | Nippon Soken, Inc. | Ceramic support capable of supporting a catalyst, a catalyst-ceramic body and processes for producing same |
| US7358210B2 (en) | 2001-03-22 | 2008-04-15 | Denso Corporation | Ceramic body and ceramic catalyst body |
| JP2010000445A (en) * | 2008-06-20 | 2010-01-07 | Asahi Kasei Corp | Catalyst for purifying lean burn automobile exhaust gas |
| KR101305182B1 (en) * | 2010-11-30 | 2013-09-12 | 현대자동차주식회사 | Highly efficient catalyst by using precious metal |
-
1995
- 1995-03-27 JP JP06761195A patent/JP3794035B2/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7223716B1 (en) | 1999-04-09 | 2007-05-29 | Nippon Soken, Inc. | Ceramic support capable of supporting a catalyst, a catalyst-ceramic body and processes for producing same |
| US7723263B2 (en) | 1999-04-09 | 2010-05-25 | Nippon Soken, Inc. | Ceramic support capable of supporting a catalyst, a catalyst-ceramic body and processes for producing same |
| US7358210B2 (en) | 2001-03-22 | 2008-04-15 | Denso Corporation | Ceramic body and ceramic catalyst body |
| JP2006297348A (en) * | 2005-04-25 | 2006-11-02 | Asahi Kasei Corp | Catalyst for clarifying exhaust gas |
| JP2010000445A (en) * | 2008-06-20 | 2010-01-07 | Asahi Kasei Corp | Catalyst for purifying lean burn automobile exhaust gas |
| KR101305182B1 (en) * | 2010-11-30 | 2013-09-12 | 현대자동차주식회사 | Highly efficient catalyst by using precious metal |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3794035B2 (en) | 2006-07-05 |
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