JP2013052376A - Exhaust gas purifying catalyst and exhaust gas purifying catalyst system containing the same - Google Patents
Exhaust gas purifying catalyst and exhaust gas purifying catalyst system containing the same Download PDFInfo
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Abstract
Description
本発明は、排ガス中の炭化水素(以下、HCと略記することもある。)の選択的酸化能を有する触媒に関する。さらに、本発明はこの触媒を用いた排ガス浄化システムに関する。 The present invention relates to a catalyst having the ability to selectively oxidize hydrocarbons in exhaust gas (hereinafter sometimes abbreviated as HC). Furthermore, the present invention relates to an exhaust gas purification system using this catalyst.
近年、地球環境保護の観点から、排ガス規制が世界的に年々強化されている。この対応策として、内燃機関においては、排ガス浄化用触媒が用いられる。この排ガス浄化用触媒において、排ガス中のハイドロカーボン(以下、HCと略記することもある。)、COおよび窒素酸化物(以下、NOxと略記することもある。)を効率的に除去するために、触媒成分としてPt、Pd、Rh等の白金族元素などを含め種々の触媒が使用されている。 In recent years, exhaust gas regulations have been strengthened worldwide year by year from the viewpoint of protecting the global environment. As a countermeasure, an exhaust gas purifying catalyst is used in an internal combustion engine. In this exhaust gas purification catalyst, in order to efficiently remove hydrocarbons (hereinafter sometimes abbreviated as HC), CO and nitrogen oxides (hereinafter also abbreviated as NOx) in the exhaust gas. Various catalysts including platinum group elements such as Pt, Pd and Rh are used as catalyst components.
従来公知の貴金属の触媒は、ストイキ条件近辺において、HC、CO、NOxを分解することが可能であるものの、いずれも資源枯渇の問題を抱えており、他の金属を用いて従来の貴金属触媒と同程度以上の浄化性能を有する触媒、または貴金属の使用量を少なくすることのできる浄化触媒が求められている。 Conventionally known noble metal catalysts are capable of decomposing HC, CO, and NOx in the vicinity of stoichiometric conditions, but all have a problem of resource depletion. There is a need for a catalyst having a purifying performance equal to or higher than that, or a purifying catalyst capable of reducing the amount of noble metal used.
しかし、例えば、卑金属の浄化触媒を用いると、貴金属触媒より浄化ウィンドウが限定的になるため、リーン〜リッチに条件が時々刻々と変動する実際の運転条件下では、HC、CO、NOxの混合物を一度に浄化することは、困難であった。 However, for example, when a base metal purification catalyst is used, the purification window becomes more limited than that of a noble metal catalyst. Therefore, under actual operating conditions in which the conditions vary from lean to rich, the mixture of HC, CO, and NOx It was difficult to clean up at once.
さらに、貴金属、卑金属を問わず従来の浄化触媒は、HCにより被毒してしまい、触媒のCO、NOx浄化機能が低下してしまうことが問題となっていた。 In addition, conventional purification catalysts, whether precious metals or base metals, are poisoned by HC, and the CO and NOx purification functions of the catalyst are degraded.
こうした背景から、浄化用触媒について種々の改良の試みがなされている。
引用文献1は、触媒活性を有する金属より選ばれた少なくとも1種の金属またはその化合物または金属酸化物を担持したリン酸塩の成形体であることを特徴とする排ガス浄化用触媒などを記載する。
Against this background, various attempts have been made to improve the purification catalyst.
Cited Document 1 describes an exhaust gas purifying catalyst characterized in that it is a molded article of a phosphate carrying at least one metal selected from metals having catalytic activity or a compound thereof or a metal oxide. .
引用文献2は、ジルコニウム、セリウム、ランタン、マンガン、コバルト、亜鉛、およびバナジウムから選択される少なくとも1種の元素で改質された固体アルミノリン酸塩組成物を含むメソ細孔性アルミノリン酸塩物質を含有する触媒組成物と、原料とを接触させることを含む、炭化水素原料を接触分解する方法などを記載する。しかし、この方法は、長鎖の炭化水素を切断する、所謂炭化水素のクラッキングであり、HCの酸化とは全く技術的思想が異なるものである。
これら公知の触媒を備えた排ガス浄化触媒では、先に分子構造の単純なCOを酸化してしまうなど、HCを選択的に酸化することのできる触媒は存在しておらず、HCを選択的に酸化できる能力の高い触媒が求められている。また、触媒の被毒を防ぐことが求められている。さらに、実際の使用条件下で、HC/CO/NOxなどの混合物を一度に浄化できる浄化システムが求められている。さらに貴金属の使用の低減が求められている。 In the exhaust gas purification catalyst equipped with these known catalysts, there is no catalyst that can selectively oxidize HC, such as oxidation of CO having a simple molecular structure. There is a need for catalysts with high ability to oxidize. There is also a need to prevent poisoning of the catalyst. Furthermore, there is a need for a purification system that can purify a mixture such as HC / CO / NOx at a time under actual use conditions. Furthermore, there is a demand for reducing the use of noble metals.
本発明者らは鋭意研究を重ねた結果、本発明の態様により上記課題を解決できることを見いだした。 As a result of intensive studies, the present inventors have found that the above problems can be solved by the embodiments of the present invention.
本発明の態様は、以下のようである。
(1)リン酸アルミニウムにジルコニウムをドープした担体上に、銅が担持されてなる、排ガス浄化触媒であって、該リン酸アルミニウム中のアルミニウムに対する該ジルコニウムのドープ量が、0.05モル比〜0.5モル比である、排ガス浄化触媒。
(2)(1)に記載の排ガス浄化触媒を前段に、Cuを担持したAl2O3の排ガス浄化触媒を後段に用いた、排ガス浄化触媒システム。
(3)(1)に記載の排ガス浄化触媒を前段に、AuとNiとからなる合金を担持したCZ排ガス浄化触媒を後段に用いた、排ガス浄化触媒システム。
Aspects of the present invention are as follows.
(1) An exhaust gas purification catalyst in which copper is supported on a carrier in which aluminum phosphate is doped with zirconium, wherein the zirconium doping amount relative to aluminum in the aluminum phosphate is 0.05 molar ratio to An exhaust gas purification catalyst having a molar ratio of 0.5.
(2) An exhaust gas purification catalyst system using the exhaust gas purification catalyst according to (1) at the front stage and an Al 2 O 3 exhaust gas purification catalyst supporting Cu at the rear stage.
(3) An exhaust gas purification catalyst system using the exhaust gas purification catalyst according to (1) in the front stage and a CZ exhaust gas purification catalyst carrying an alloy of Au and Ni in the rear stage.
本発明の態様により、驚くべきことに、HC、NOx、CO等を含む排ガスにおいて、HCを選択的に酸化できる触媒を提供することが可能となる。それにより触媒の被毒を解決できる。さらにこの本発明の態様に係る触媒は、HC酸化によりCOを生成して還元雰囲気としてNOx浄化を促進するため、還元雰囲気下でしかNOxを還元できなかった卑金属等の触媒であっても、本発明の態様に係る触媒を組み合わせることにより、リーン〜リッチの変動条件下においても、HC、CO、NOxの混合物を一度に浄化できる排ガス触媒システムを提供することが可能となる。さらに本発明に係る触媒により、貴金属使用量の低減を達成することが可能となる。 The aspect of the present invention surprisingly makes it possible to provide a catalyst capable of selectively oxidizing HC in exhaust gas containing HC, NOx, CO and the like. Thereby, poisoning of the catalyst can be solved. Furthermore, since the catalyst according to this embodiment of the present invention generates CO by HC oxidation and promotes NOx purification as a reducing atmosphere, even a catalyst such as a base metal that could reduce NOx only under a reducing atmosphere, By combining the catalyst according to the aspect of the invention, it is possible to provide an exhaust gas catalyst system that can purify a mixture of HC, CO, and NOx at a time even under lean to rich fluctuation conditions. Furthermore, the catalyst according to the present invention can achieve a reduction in the amount of noble metal used.
なお、本明細書中において、無機物の化合物の名称、または(下記に例示するような)含有される金属の比を用いた表記により、これらの組成を有するように生成させても、不純物などを含めて現実的に生成してしまう組成をも含むものとする。したがって、無機物の化合物の名称または含有される金属の比を用いた表記により、例えば、無機化合物の構造中において、例えば、酸素、水素、窒素などの元素が、化学式中±1原子比以下で過剰または過少に存在している組成の無機化合物、すなわち、例えばAlPO4中でOの場合のAlPO3〜AlPO5をも含み、さらに化合物中に表記されていない水素を不純物として有するものなどをも含む。そして例えば、リン酸ジルコニウムアルミニウムはまた、含有されるドープ金属と担持される元素の比などに着目して、例えば、Al0.8Zr0.2POとも表記される。 Note that in this specification, impurities or the like may be generated even if they are generated so as to have these compositions by the name of the inorganic compound or the notation using the ratio of the contained metal (as exemplified below). Including a composition that is actually generated. Therefore, according to the notation using the name of the inorganic compound or the ratio of the contained metal, for example, in the structure of the inorganic compound, for example, elements such as oxygen, hydrogen, and nitrogen are excessive in a chemical formula of ± 1 atomic ratio or less. Or, an inorganic compound having a composition which is present in a small amount, that is, an AlPO 3 to AlPO 5 in the case of O in AlPO 4 , for example, and also having hydrogen not represented in the compound as an impurity . For example, aluminum zirconium phosphate is also expressed as, for example, Al 0.8 Zr 0.2 PO, focusing on the ratio of the doped metal contained and the supported element.
本発明に係る排ガス浄化触媒システム1は、図3に示すように、エンジン2からの排ガス通路3の、例えばA/F計4の下流に設けられ、排ガス通路に設けられている。そして、HC酸化触媒5およびNOx還元触媒6は、それぞれ排ガス浄化触媒システム1中の、上流に近い前段および下流に近い後段に設けられている。
As shown in FIG. 3, the exhaust gas purification catalyst system 1 according to the present invention is provided in the
本発明に係るHC酸化触媒は、上記のように、まず、ドープ金属として、ジルコニウム(Zr)を使用して、リン酸アルミニウム中にドープするものである。ドープの形態については、特に制限なく、リン酸アルミニウム中に少量のジルコニウムがおおよそ一様にドープされていればよい。 As described above, the HC oxidation catalyst according to the present invention is first doped into aluminum phosphate using zirconium (Zr) as the dope metal. The form of doping is not particularly limited as long as a small amount of zirconium is almost uniformly doped in aluminum phosphate.
ジルコニウムのリン酸アルミニウム中のアルミニウムに対するドープ量は、0.01モル比以上、0.05モル比以上、0.1モル比以上であることができ、0.7モル比以下、0.5モル比以下、0.4モル比以下であることができる。ジルコニウムのドープ量は、HCの選択的浄化可性能を高める上では、0.05モル比以上、0.5モル比以下であることが好ましい。 The doping amount of zirconium with respect to aluminum in aluminum phosphate can be 0.01 mole ratio or more, 0.05 mole ratio or more, 0.1 mole ratio or more, 0.7 mole ratio or less, 0.5 mole ratio or less. Ratio or less, and 0.4 mole ratio or less. The doping amount of zirconium is preferably 0.05 mole ratio or more and 0.5 mole ratio or less in order to enhance the selective purifying performance of HC.
本発明に係るHC酸化触媒は、上記ジルコニウムをドープしたリン酸アルミニウムに、さらに銅(Cu)を担持させて成るものである。担持の形態については、特に制限なく、ジルコニウムドープリン酸アルミニウム上に銅がおおよそ一様に担持されていればよい。 The HC oxidation catalyst according to the present invention is formed by further supporting copper (Cu) on the aluminum phosphate doped with zirconium. There is no particular limitation on the form of loading, as long as copper is supported substantially uniformly on the zirconium-doped aluminum phosphate.
担持される銅の粒径は、特に制約されないが、例えば、1nm以上、5nm以上、10nm以上であることができ、500nm以下、400nm以下、300nm以下であることができる。 The particle size of the supported copper is not particularly limited, but can be, for example, 1 nm or more, 5 nm or more, 10 nm or more, and can be 500 nm or less, 400 nm or less, or 300 nm or less.
銅のジルコニウムドープリン酸アルミニウムに対する量は、0.01wt%以上、0.1wt%以上、0.5wt%以上であることができ、30wt%以下、20wt%以下、10wt%以下であることができる。 The amount of copper with respect to zirconium-doped aluminum phosphate can be 0.01 wt% or more, 0.1 wt% or more, 0.5 wt% or more, and can be 30 wt% or less, 20 wt% or less, 10 wt% or less. .
上記のアルミニウム塩とジルコニウム塩を含む混合溶液において用いられる溶媒としては、これらの金属塩を溶解させることができる任意の溶媒、例えば、水などの水性溶媒や有機溶媒等を使用することができる。一般的には、アルミニウム塩とジルコニウム塩は、最終的に得られる金属粒子中のアルミニウムとジルコニウムのモル比になるように上記の溶媒中に添加することができる。 As a solvent used in the mixed solution containing the above aluminum salt and zirconium salt, any solvent that can dissolve these metal salts, for example, an aqueous solvent such as water, an organic solvent, or the like can be used. In general, an aluminum salt and a zirconium salt can be added to the above-mentioned solvent so as to obtain a molar ratio of aluminum and zirconium in the finally obtained metal particles.
リン酸アルミニウムにジルコニウムをドープさせる方法としては、リン酸アルミニウム中のアルミニウム原子をジルコニウムに置換できる方法であれば特に制限なく、例えば、硝酸アルミニウムおよび硝酸ジルコニルの水溶液中に、リン酸水溶液を加え、さらにアンモニア水を加えてpHを調整するといった、中和法などの公知の方法を用いることができる。 The method for doping aluminum phosphate with zirconium is not particularly limited as long as the aluminum atom in aluminum phosphate can be replaced with zirconium. For example, an aqueous solution of phosphoric acid is added to an aqueous solution of aluminum nitrate and zirconyl nitrate, Furthermore, a known method such as a neutralization method in which ammonia water is added to adjust the pH can be used.
ジルコニウムをドープしたリン酸アルミニウムに銅を担持させる方法としては、特に制限なく、共沈法、含浸法、浸漬法、イオン交換法、乾式混合法、湿式混合法などの公知の方法を用いることができる。 The method for supporting copper on zirconium phosphate-doped aluminum phosphate is not particularly limited, and known methods such as coprecipitation, impregnation, immersion, ion exchange, dry mixing, and wet mixing can be used. it can.
上記製造方法において、アルミニウム、ジルコニウムおよび銅の化合物については、特に限定はなく、例えば、市販の、塩化物、硝酸塩、酢酸塩、炭酸塩等を使用することができる。 In the above production method, the aluminum, zirconium, and copper compounds are not particularly limited, and for example, commercially available chlorides, nitrates, acetates, carbonates, and the like can be used.
また、本発明に係るHC酸化触媒の焼成温度は、300℃以上、400℃以上、500℃以上、600℃以上であることができ、1100℃以下、1000℃以下、900℃以下、800℃以下であることができる。 Also, the calcination temperature of the HC oxidation catalyst according to the present invention can be 300 ° C. or more, 400 ° C. or more, 500 ° C. or more, 600 ° C. or more, 1100 ° C. or less, 1000 ° C. or less, 900 ° C. or less, 800 ° C. or less. Can be.
焼成温度が、400℃より低いとアンモニウム塩の除去が不完全になり、1000℃より高いと触媒の比表面積の低下が著しくなって、単体のAlPO4とあまり変わらなくなってしまうことから、400℃以上、1000℃以下であることが好ましい。さらに比表面積で単体のAlPO4の2倍以上に相当する200m2/g以上とすることができることから、500℃以上、900℃以下であるとより好ましい。 When the calcination temperature is lower than 400 ° C., the removal of the ammonium salt becomes incomplete. When the calcination temperature is higher than 1000 ° C., the specific surface area of the catalyst is remarkably lowered, so that it is not much different from the single AlPO 4. As mentioned above, it is preferable that it is 1000 degrees C or less. Further, the specific surface area can be 200 m 2 / g or more, which corresponds to twice or more of a single AlPO 4 , and therefore, it is more preferably 500 ° C. or more and 900 ° C. or less.
本発明に係るHC酸化触媒は、特に制限なく、ハニカム、円柱状、球状などのペレット、発泡体に形成されることができる。 The HC oxidation catalyst according to the present invention is not particularly limited, and can be formed into a honeycomb, a cylindrical pellet, a spherical pellet, or a foam.
さらに、本発明に係るHC酸化触媒は、NOx還元触媒と組み合わせることができる。
特に、NOx還元触媒がHC、O2の存在によって、失活する傾向を有する場合には、本発明に係る触媒をNOx還元触媒の前段に置いて、触媒システムとして組み合わせて使用すれば、NOx還元触媒の性能を低下させることなく好ましい。さらに、このNOx還元触媒が、例えば、酸化剤と還元剤が当量存在するストイキ〜リーン雰囲気下においてもNOxを還元できる場合には、燃費向上を達成でき、より好ましい。
Furthermore, the HC oxidation catalyst according to the present invention can be combined with a NOx reduction catalyst.
In particular, when the NOx reduction catalyst has a tendency to be deactivated due to the presence of HC and O 2 , the NOx reduction can be achieved by using the catalyst according to the present invention in combination with the catalyst system in front of the NOx reduction catalyst. It is preferable without degrading the performance of the catalyst. Further, this NOx reduction catalyst is more preferable, for example, when NOx can be reduced even in a stoichiometric to lean atmosphere where an equivalent amount of oxidizing agent and reducing agent is present.
本発明に係る触媒と組み合わせることのできるNOx還元触媒としては、例えば、種々の組成範囲を有する、AuとNiとからなる合金を担持したCeO2とZrOとからなる触媒(以下、CeO2とZrOとからなる触媒をCZと省略する場合がある。)、銅を担持したAl2O3などを挙げることができるが、これらに限られない。 As the NOx reduction catalyst that can be combined with the catalyst according to the present invention, for example, a catalyst composed of CeO 2 and ZrO carrying an alloy composed of Au and Ni having various composition ranges (hereinafter referred to as CeO 2 and ZrO). In some cases, CZ may be abbreviated as CZ.), Al 2 O 3 supporting copper, and the like.
本発明が実施形態により、制約されることを意図しないが、より理解の助けとするために、以下に、例示的に実施例および比較例を記載する。 While the present invention is not intended to be limited by the embodiments, the following examples and comparative examples are given by way of illustration in order to aid in better understanding.
以下の各例において、用いた測定法、測定装置、その他の装置、サンプル等について記載する。
(測定法および測定装置)
(触媒の組成の測定)
XRD(X線回折:X−Ray Diffraction)(PHILIPS製X′PertMRD)によりバルク全体の組成を測定した。
なお、具体的な測定条件は以下のとおりである。
測定方法: FT法(Fixed Time法)
X線源: CuKα
ステップ幅: 0.02deg.
計数時間: 0.5s
発散スリット(DS):2/3deg.
散乱スリット(SS):2/3deg.
受光スリット(RS):0.5mm
管電圧: 50kV
管電流: 300mA
In each of the following examples, the measurement method, measurement apparatus, other apparatus, sample, etc. used are described.
(Measurement method and measuring equipment)
(Measurement of catalyst composition)
The composition of the entire bulk was measured by XRD (X-Ray Diffraction) (X'PertMRD manufactured by PHILIPS).
Specific measurement conditions are as follows.
Measuring method: FT method (Fixed Time method)
X-ray source: CuKα
Step width: 0.02 deg.
Counting time: 0.5s
Divergent slit (DS): 2/3 deg.
Scattering slit (SS): 2/3 deg.
Receiving slit (RS): 0.5mm
Tube voltage: 50 kV
Tube current: 300mA
(ナノ粒子の粒子形状と粒度分布の測定)
TEM(Transmission Electron Microscope 透過型電子顕微鏡)(日立製作所(株)社製 HD−2000、加速電圧:200kV)を用いてナノ粒子について形状と粒度分布を測定した。
(Measurement of particle shape and particle size distribution of nanoparticles)
The shape and particle size distribution of the nanoparticles were measured using TEM (Transmission Electron Microscope Transmission Electron Microscope) (Hitachi Ltd., HD-2000, acceleration voltage: 200 kV).
(ナノ粒子の元素分析の測定)
TEM−EDS(EDS:エネルギー分散型X線分光法)(日立製作所(株)社製 HD−2000、加速電圧:200kV)を用いて、ナノ粒子の組成比を測定した。
(Measurement of elemental analysis of nanoparticles)
The composition ratio of the nanoparticles was measured using TEM-EDS (EDS: Energy Dispersive X-ray Spectroscopy) (HD-2000 manufactured by Hitachi, Ltd., acceleration voltage: 200 kV).
(比表面積の測定)
測定方法としてBET吸着法により、比表面積を測定した。
(Measurement of specific surface area)
The specific surface area was measured by the BET adsorption method as a measuring method.
(触媒活性の測定)
下記触媒ペレットをガラス反応管(内側直径:20mm)に厚さ(15mm)で詰め、ガラスウールで固定する。あらかじめ混合したモデル排ガスを、空間速度(SV)200000/時間で、ガラスの反応管に流して、触媒を通過させた。ガスの温度は18℃/分の昇温速度で100℃から600℃まで上昇させた。
HCの場合、HC濃度は、赤外分光光度計(メーカー名;(株)堀場製作所、型番:MEXA−7100H)を用いて測定した。
NOxの場合、NOx濃度は排ガス分析計(堀場製作所 MEXA7100H)で測定した。
(その他の装置類)
遠心分離器:メーカー名;国産遠心器(株)、品番:H−700
(Measurement of catalytic activity)
The following catalyst pellets are packed in a glass reaction tube (inner diameter: 20 mm) with a thickness (15 mm) and fixed with glass wool. The premixed model exhaust gas was passed through a glass reaction tube at a space velocity (SV) of 200000 / hour to pass the catalyst. The temperature of the gas was increased from 100 ° C. to 600 ° C. at a rate of temperature increase of 18 ° C./min.
In the case of HC, the HC concentration was measured using an infrared spectrophotometer (manufacturer name: Horiba, Ltd., model number: MEXA-7100H).
In the case of NOx, the NOx concentration was measured with an exhaust gas analyzer (Horiba MEXA7100H).
(Other devices)
Centrifuge: Manufacturer name; Domestic centrifuge, product number: H-700
(合成例1)
30g(80ミリモル)の硝酸アルミニウム・9水和物および5.35g(20ミリモル)の硝酸ジルコニル・2水和物を、それぞれ100mLのイオン交換水中に溶解させた。100mLの上記硝酸アルミニウム水溶液中に、85wt%リン酸13.84gを含む水溶液1200mlを加えた後、これに100mLの上記硝酸ジルコニル水溶液を混合させた、この混合物に対し28wt%のアンモニア水を滴下して、pHが3.5〜4.5になるように調整して、室温下で12時間攪拌した。目視による観察では、生成された溶液は白濁していた。
(Synthesis Example 1)
30 g (80 mmol) of aluminum nitrate nonahydrate and 5.35 g (20 mmol) of zirconyl nitrate dihydrate were each dissolved in 100 mL of ion-exchanged water. After adding 1200 ml of an aqueous solution containing 13.84 g of 85 wt% phosphoric acid to 100 mL of the above aqueous aluminum nitrate solution, 28 ml of aqueous ammonia was added dropwise to this mixture in which 100 mL of the above zirconyl nitrate aqueous solution was mixed. The pH was adjusted to 3.5 to 4.5, and the mixture was stirred at room temperature for 12 hours. As a result of visual observation, the produced solution was cloudy.
この白濁した水溶液を、遠心分離器を用いて、3000回転/分で15分間遠心分離を行い、水溶液を沈殿物と上澄み液に分離し、この沈殿物を、イオン交換水を用いて2回洗浄し、次に室湿度下120℃で12時間乾燥した。得られた乾燥物を破砕して、室湿度下500℃で2時間焼成した。焼成物を室温まで放冷させ、さらに破砕して14.7gの白色の、ジルコニウムがドープされたリン酸アルミニウム粉末が得られた。 The white turbid aqueous solution is centrifuged at 3000 rpm for 15 minutes using a centrifuge to separate the aqueous solution into a precipitate and a supernatant, and this precipitate is washed twice with ion-exchanged water. And then dried at 120 ° C. for 12 hours under room humidity. The obtained dried product was crushed and fired at 500 ° C. for 2 hours under room humidity. The fired product was allowed to cool to room temperature and further crushed to obtain 14.7 g of a white zirconium-doped aluminum phosphate powder.
銅の担持は、以下に説明する含浸法を用いて行った。ジルコニウムがドープされたリン酸アルミニウム粉末10gを、200mLのイオン交換水中に分散させ、次に、50mLのイオン交換水中に溶解させた1.71g(7.9ミリモル)の酢酸銅(II)一水和物を室温下で加え、次に、この水溶液を攪拌しながら、120℃〜150℃に昇温して水を蒸発させて、9.4gの乾燥物を得た。この乾燥物を破砕して、室湿度下500℃で2時間焼成し、室温まで放冷後、焼成物を破砕して触媒粉末を得た。 Copper loading was performed using the impregnation method described below. Zirconium doped aluminum phosphate powder 10 g was dispersed in 200 mL of ion exchange water and then dissolved in 50 mL of ion exchange water 1.71 g (7.9 mmol) of copper (II) acetate monohydrate. The Japanese product was added at room temperature, and then this aqueous solution was stirred and heated to 120 ° C. to 150 ° C. to evaporate water to obtain 9.4 g of a dried product. The dried product was crushed and calcined at 500 ° C. for 2 hours under room humidity. After cooling to room temperature, the calcined product was crushed to obtain a catalyst powder.
(触媒ペレットの作製)
上記触媒粉末をプレス機を用いて、100MPaで加圧した後、これを解砕したものを用いて評価した。
(Production of catalyst pellets)
After pressurizing the catalyst powder at 100 MPa using a press machine, the catalyst powder was crushed and evaluated.
モデル排ガスとしては、体積で、CO:0.6%、C3H6:1000ppm、NO:3000ppm、O2:0.44%、H2O:3%、N2:残余の組成(A/F=14.4相当、リッチ雰囲気)のガス(モデル排ガス1)を用いた。 As model exhaust gas, by volume, CO: 0.6%, C 3 H 6 : 1000 ppm, NO: 3000 ppm, O 2 : 0.44%, H 2 O: 3%, N 2 : residual composition (A / F = 14.4 equivalent (rich atmosphere) gas (model exhaust gas 1) was used.
(実施例1)
Al:Zr=0.8;0.2(モル比)になるようにして生成された銅を担持したジルコニウムドープリン酸アルミニウム触媒(Cuを担持したAl0.8Zr0.2PO)触媒の浄化プロファイルを、上記(モデル排ガス1)を用い、上記(触媒活性の測定)に従って測定した。このAl0.8Zr0.2POの比表面積は、107m2/gであった。銅の担持量は、Al0.8Zr0.2POに対して5wt%であった。その結果を図1に示す。
Example 1
Al: Zr = 0.8; of the zirconium-doped aluminum phosphate catalyst (Cu-supported Al 0.8 Zr 0.2 PO) catalyst supporting copper produced so as to be 0.2 (molar ratio) The purification profile was measured according to the above (measurement of catalytic activity) using the above (model exhaust gas 1). The specific surface area of this Al 0.8 Zr 0.2 PO was 107 m 2 / g. The amount of copper supported was 5 wt% with respect to Al 0.8 Zr 0.2 PO. The result is shown in FIG.
図1に示すように、C3H6の浄化は昇温と共に進行するが、COの浄化はほとんど進行しなかった。そして排ガス中のC3H6の濃度が低下すると、COの浄化が約500℃近辺から開始した。 As shown in FIG. 1, the purification of C 3 H 6 proceeds with increasing temperature, but the purification of CO hardly progressed. When the concentration of C 3 H 6 in the exhaust gas decreased, CO purification started from around 500 ° C.
上記のように、本発明に係る、Cuを担持したAl0.8Zr0.2PO触媒は、排ガス中のHCを選択的に浄化できることが確認できた。 As described above, it was confirmed that the Al 0.8 Zr 0.2 PO catalyst supporting Cu according to the present invention can selectively purify HC in the exhaust gas.
(実施例2)
Al:Zr=0.9:0.1(モル比)である点を除き実施例1の手順に従ってサンプルを作製し、同様に評価したところ、実施例1とほぼ同様の選択的HC浄化機能を有することが確認された。
(Example 2)
A sample was prepared according to the procedure of Example 1 except that Al: Zr = 0.9: 0.1 (molar ratio) and evaluated in the same manner. As a result, a selective HC purification function almost similar to that of Example 1 was obtained. It was confirmed to have.
(比較例1)
上記(合成例1)において、硝酸ジルコニル・1水和物を用いなかったほかは、(合成例1)と同様に手順により、比較例1の評価サンプルを作製した。このAlPO4の比表面積は、104m2/gであり、銅の担持量は、AlPO4に対して5wt%であった。生成された銅を担持したリン酸アルミニウム触媒(Cuを担持したAlPO4)についての浄化プロファイルを、(実施例1)と同様に測定した。その結果を図2に示す。
(Comparative Example 1)
An evaluation sample of Comparative Example 1 was prepared in the same manner as in (Synthesis Example 1) except that zirconyl nitrate monohydrate was not used in (Synthesis Example 1). The specific surface area of this AlPO 4 was 104 m 2 / g, and the supported amount of copper was 5 wt% with respect to AlPO 4 . The purification profile of the produced aluminum phosphate catalyst supporting copper (AlPO 4 supporting Cu) was measured in the same manner as in Example 1. The result is shown in FIG.
図2に示すように、COの浄化が先に始まり、その後にC3H6の浄化が進行した。何らかの理論に拘束されることを意図しないが、380℃近辺からのCO濃度の増加は、C3H6の不完全酸化によるものと考えられる。 As shown in FIG. 2, CO purification started first, followed by C 3 H 6 purification. Without intending to be bound by any theory, it is believed that the increase in CO concentration from around 380 ° C. is due to incomplete oxidation of C 3 H 6 .
上記のように、比較例1のCuを担持したAlPO4触媒は、排ガス中のHCを選択的に浄化できる機能を有さないことが確認された。 As described above, it was confirmed that the AlPO 4 catalyst supporting Cu of Comparative Example 1 did not have a function of selectively purifying HC in the exhaust gas.
(参考合成例1)
硝酸鉄(III)水溶液を用いた含浸担持法により、Feを担持したAl2O3触媒を得た。
(Reference Synthesis Example 1)
An Fe 2 -supported Al 2 O 3 catalyst was obtained by an impregnation support method using an iron (III) nitrate aqueous solution.
(実施例3)
(実施例1)で得られた触媒(実施例3)と、(参考合成例1)で得られたNOx触媒(比較例2)とをC3H6転化率、O2転化率、CO残存率の3項目で評価した。
500℃の一定温度である点を除き、上記(モデル排ガス1)を用い、上記(触媒活性の測定)の手順に基づいて測定した。
(Example 3)
The catalyst (Example 3) obtained in (Example 1) and the NOx catalyst (Comparative Example 2) obtained in (Reference Synthesis Example 1) were converted to C 3 H 6 , O 2 conversion, and CO remaining. Evaluation was made on three items.
Except for the constant temperature of 500 ° C., the above (model exhaust gas 1) was used, and the measurement was performed based on the above procedure (measurement of catalytic activity).
実施例3(5wt%Cuを担持したAl0.8Zr0.2PO):
C3H6転化率 100%、O2転化率85%、CO残存率95%
比較例2(5wt%Feを担持したAl2O3):
C3H6転化率 41%、O2転化率31%、CO残存率78%
Example 3 (Al 0.8 Zr 0.2 PO supporting 5 wt% Cu):
C 3 H 6 conversion rate 100%, O 2 conversion rate 85%, CO residual rate 95%
Comparative Example 2 (Al 2 O 3 supporting 5 wt% Fe):
C 3 H 6 conversion 41%, O 2 conversion 31%, CO residual rate 78%
上記(実施例3)および(比較例2)の結果から明らかなように、(実施例3)の触媒の方がHCを選択的に酸化する能力が高く、触媒を通ったガス流中のCOの量が多いことが判明した。 As is clear from the results of (Example 3) and (Comparative Example 2) above, the catalyst of (Example 3) has a higher ability to selectively oxidize HC, and the CO in the gas stream passing through the catalyst is higher. The amount of was found to be large.
(参考合成例2)
硝酸銅(II)水溶液を用いた含浸担持法により、Cuを担持したAl2O3触媒を得た。
(Reference Synthesis Example 2)
An Al 2 O 3 catalyst supporting Cu was obtained by an impregnation supporting method using an aqueous copper (II) nitrate solution.
(実施例4)
(実施例1)で得られた触媒を前段に配置し(参考合成例2)で得られたNOx触媒を後段に配置した触媒システム(実施例4)、(参考合成例1)で得られた触媒を前段に配置し(参考合成例2)で得られたNOx触媒を後段に配置した触媒システム(比較例3)について、実施例2と同じ条件下で、500℃におけるNOxの転化率を測定した。
Example 4
The catalyst system obtained in (Example 1) was placed in the previous stage and the NOx catalyst obtained in (Reference Synthesis Example 2) was placed in the subsequent stage (Example 4), and obtained in (Reference Synthesis Example 1). Measurement of NOx conversion rate at 500 ° C. under the same conditions as in Example 2 for the catalyst system (Comparative Example 3) in which the catalyst was placed in the previous stage and the NOx catalyst obtained in the Reference Synthesis Example 2 was placed in the subsequent stage. did.
実施例4(5wt%Cuを担持したAl0.8Zr0.2PO+5wt%Cuを担持したAl2O3) 100%
比較例3(5wt%Feを担持したAl2O3+5wt%Cuを担持したAl2O3) 55%
Example 4 (Al 0.8 Zr 0.2 PO supporting 5 wt% Cu + Al 2 O 3 supporting 5 wt% Cu) 100%
Comparative Example 3 (Al 2 O 3 carrying 5 wt% Fe carrying Al 2 O 3 + 5wt% Cu ) 55%
上記(実施例4)、(比較例3)の結果から明らかなように、HCを選択的に酸化できる(実施例4)の触媒システムの方が、NOx浄化能力が高いことが判明した。 As is apparent from the results of the above (Example 4) and (Comparative Example 3), it was found that the catalyst system capable of selectively oxidizing HC (Example 4) has a higher NOx purification capacity.
(参考合成例3)
(AuとNiとからなる合金ナノ粒子の合成)
二又フラスコ中で120mLの無水エチレングリコールに1.1gのポリ−n−ビニルピロリドン(PVP)(製造メーカー名:和光純薬工業(株))を加えた。この混合物に0.1404gの硫酸ニッケルを加えて80℃で3時間撹拝して、溶液(溶液1)を得た。
(Reference Synthesis Example 3)
(Synthesis of alloy nanoparticles composed of Au and Ni)
In a bifurcated flask, 1.1 g of poly-n-vinylpyrrolidone (PVP) (manufacturer: Wako Pure Chemical Industries, Ltd.) was added to 120 mL of anhydrous ethylene glycol. 0.1404 g of nickel sulfate was added to this mixture and stirred at 80 ° C. for 3 hours to obtain a solution (solution 1).
別に、二又フラスコ中で蒸留水50mLに0.1809gの塩化金酸(HAuCl4)を入れ、2時間以上強く撹拝し溶解させて、濃い赤色溶液(溶液2)を得た。
溶液1を冷却バスで0℃まで冷却し、フラスコ中の溶液1に溶液2を注ぎ均一に撹拝した。混合溶液のpHが10となるように1M NaOH溶液(約5mL)で調整した。この混合溶液をオイルバスで100℃に加熱し、攪拌しながら2時間保持した。その後、オイルバスからフラスコを引き上げて、コロイド懸濁液が室温に冷却されるまで放置した。フラスコ内の全てのイオンを完全に還元するため、水素化ホウ素ナトリウム0.038gを加え、その後懸濁液をしばらく放置した。
Separately, 0.1809 g of chloroauric acid (HAuCl 4 ) was added to 50 mL of distilled water in a bifurcated flask and stirred vigorously for 2 hours or more to obtain a dark red solution (solution 2).
Solution 1 was cooled to 0 ° C. with a cooling bath, and
生成したナノ粒子は、所定量のナノ粒子を含む一定分量を多量のアセトンで処理し、精製した。これにより、保護PVPはアセトンの相に抽出され、メタルのナノ粒子が凝集した。上澄み液を移す(デカンテーション)か、または3000回転/分で15分間の遠心分離によりコロイドを取り出した。アセトン相を取り除いた後、精製したコロイドは純エタノール中に緩やかな攪拌で分散させた。 The produced nanoparticles were purified by treating an aliquot containing a predetermined amount of nanoparticles with a large amount of acetone. Thereby, the protective PVP was extracted into the acetone phase, and the metal nanoparticles aggregated. The supernatant was removed (decantation) or the colloid was removed by centrifugation at 3000 rpm for 15 minutes. After removing the acetone phase, the purified colloid was dispersed in pure ethanol with gentle stirring.
(参考合成例4)
(AuとNiとからなる合金ナノ粒子のCZ触媒への担持)
100mLのシュレンク管に1gのCeO2とZrOとからなる触媒(CZ)を入れた。シュレンク管内を真空に引き、N2を流し込んで配管を洗浄し完全に空気を取り除いた。先に合成したコロイドの懸濁液(精製したものと残りの液との両方)については濃度を把握しておき、Rhに対し、それぞれ0.5wt%相当のAu、Ni金属量を含む精製コロイド懸濁液を、ゴムのセブタムを通してシュレンク管に注入した。混合物を室温で3時間撹拝し、溶媒を減圧除去した。その後、コロイド沈殿物の残りの高分子保護剤を取り除くため、200〜600℃の真空ポンプ減圧下または空気中で焼成した。得られた触媒粉末は、上記の手順に従って成型し、AuとNiと(モル比で50:50)からなる合金を担持したCZ触媒を得た。
(Reference Synthesis Example 4)
(Support of alloy nanoparticles made of Au and Ni on CZ catalyst)
A 100 mL Schlenk tube was charged with 1 g of a catalyst (CZ) consisting of CeO 2 and ZrO. The Schlenk tube was evacuated and N 2 was flown into it to clean the piping and completely remove the air. The concentration of the previously synthesized colloidal suspension (both purified and remaining liquid) is known, and the purified colloid contains the amount of Au and Ni metal equivalent to 0.5 wt% relative to Rh, respectively. The suspension was injected into the Schlenk tube through a rubber cebutam. The mixture was stirred at room temperature for 3 hours and the solvent removed in vacuo. Thereafter, in order to remove the remaining polymer protective agent from the colloidal precipitate, it was calcined under reduced pressure of a vacuum pump of 200 to 600 ° C. or in air. The obtained catalyst powder was molded according to the above procedure to obtain a CZ catalyst carrying an alloy composed of Au and Ni (molar ratio 50:50).
(触媒の分析)
得られたAuとNiと(モル比で50:50)からなる合金を担持したCZ触媒について、合金粒子の形状、粒度分布、元素分析をTEMおよびTEM−EDSで行った。
ナノ粒子のサイズは、3.61nm±0.9nmであった。
また、銅被覆グリッド上のAuとNiと(モルで50:50)からなる合金のコロイドについて測定したTEM−EDSスペクトルから、任意の各々の粒子がAu、Niを含むことを示した。
(Catalyst analysis)
About the CZ catalyst which carry | supported the alloy which consists of obtained Au and Ni (molar ratio 50:50), the shape of the alloy particle, the particle size distribution, and the elemental analysis were performed by TEM and TEM-EDS.
The size of the nanoparticles was 3.61 nm ± 0.9 nm.
Moreover, it was shown from the TEM-EDS spectrum measured about the colloid of the alloy which consists of Au and Ni (molar 50:50) on a copper covering grid, that each arbitrary particle | grain contains Au and Ni.
(実施例5)
(実施例1)で得られた触媒を前段に配置し(参考合成例4)で得られたNOx触媒を後段に配置した触媒システム(実施例5)、(参考合成例4)で得られたNOx触媒のみを使用した触媒システム(比較例4)、(参考合成例1)で得られた触媒を前段に配置し(参考合成例4)で得られたNOx触媒を後段に配置した触媒システム(比較例5)、(実施例1)で得られた触媒の代わりに(合成例1)においてAl0.8Zr0.2POの代わりにZSM−5を用いて得た、5wt%Cuを担持したZSM−5触媒を前段に配置し(参考合成例4)で得られたNOx触媒を後段に配置した触媒システム(比較例6)について、500℃の一定温度である点、およびモデル排ガス流は、体積で、NO:1500ppm、O2:0.7%、C3H6:1000ppm、CO:0.65%、CO2:10%、H2O:3%、残余はN2(モデル排ガス2、A/F=14.6相当、ストイキ雰囲気)であった点を除き、上記(触媒活性の測定)の手順に基づいて、下記の触媒および種々のガス流について、500℃におけるNOxの転化率を測定した。
(Example 5)
The catalyst system obtained in (Example 1) was placed in the previous stage, and the NOx catalyst obtained in (Reference Synthesis Example 4) was placed in the subsequent stage (Example 5), and obtained in (Reference Synthesis Example 4). Catalyst system using only NOx catalyst (Comparative Example 4), catalyst system obtained by placing the catalyst obtained in (Reference Synthesis Example 1) in the previous stage and placing the NOx catalyst obtained in (Reference Synthesis Example 4) in the subsequent stage ( 5 wt% Cu obtained by using ZSM-5 instead of Al 0.8 Zr 0.2 PO in (Synthesis Example 1) instead of the catalyst obtained in Comparative Example 5) and (Example 1) The catalyst system (Comparative Example 6) in which the ZSM-5 catalyst thus prepared was placed in the previous stage and the NOx catalyst obtained in the Reference Synthesis Example 4 was placed in the latter stage was compared with the point that the temperature was constant at 500 ° C. and the model exhaust gas flow , by volume, NO: 1500ppm, O 2: 0.7% C 3 H 6: 1000ppm, CO : 0.65%, CO 2: 10%, H 2 O: 3%, remainder N 2 (
実施例5(5wt%Cuを担持したAl0.8Zr0.2PO+5wt%AuとNiとからなる合金を担持したCZ) 87%
比較例4(5wt%AuとNiとからなる合金を担持したCZのみ) 4%
比較例5(5wt%Feを担持したAl2O3+5wt%AuとNiとからなる合金を担持したCZ) 34%
比較例6(5wt%Cuを担持したZSM−5+5wt%AuとNiとからなる合金を担持したCZ) 7%
Example 5 (CZ carrying an alloy consisting of Al 0.8 Zr 0.2 PO carrying 5 wt% Cu + 5 wt% Au and Ni) 87%
Comparative Example 4 (only CZ carrying an alloy composed of 5 wt% Au and Ni) 4%
Comparative Example 5 (Al 2 O 3 supporting 5 wt% Fe + CZ supporting an alloy of 5 wt% Au and Ni) 34%
Comparative Example 6 (ZSM-5 supporting 5 wt% Cu + CZ supporting an alloy consisting of 5 wt% Au and Ni) 7%
上記(実施例5)、(比較例4)〜(比較例6)の結果から明らかなように、HC酸化触媒としてCuを担持したAl0.8Zr0.2POを前段に配置した触媒システムは、ストイキ雰囲気下においてもHC/CO/NOxを浄化できることが示された。 As is clear from the results of (Example 5) and (Comparative Example 4) to (Comparative Example 6), a catalyst system in which Al 0.8 Zr 0.2 PO supporting Cu as an HC oxidation catalyst is arranged in the previous stage. It was shown that HC / CO / NOx can be purified even under a stoichiometric atmosphere.
本発明によれば、資源枯渇の恐れのある白金族金属を用いることなく、HCを選択的に酸化できる触媒を提供でき、さらに、この触媒は、幅広い排ガス組成において、HCが存在すると活性が充分でなかった触媒との組み合わせをも可能にすることができる。 According to the present invention, it is possible to provide a catalyst that can selectively oxidize HC without using a platinum group metal that may be depleted of resources. Furthermore, this catalyst is sufficiently active in the presence of HC in a wide range of exhaust gas compositions. Combinations with catalysts that were not possible can also be made possible.
1 排ガス浄化触媒システム
2 エンジン
3 排ガス通路
4 A/F計
5 HC酸化触媒
6 NOx還元触媒
1 exhaust gas
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