JP2012055857A - Catalyst for purifying exhaust gas - Google Patents
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- 239000003054 catalyst Substances 0.000 title claims abstract description 36
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 27
- 239000010419 fine particle Substances 0.000 claims abstract description 25
- 239000007789 gas Substances 0.000 claims abstract description 22
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000001301 oxygen Substances 0.000 claims abstract description 12
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 12
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 7
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 7
- 239000002245 particle Substances 0.000 claims description 22
- 238000004519 manufacturing process Methods 0.000 claims description 10
- 239000010953 base metal Substances 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 12
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 68
- 239000000243 solution Substances 0.000 description 30
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 21
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 21
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 21
- 238000000746 purification Methods 0.000 description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 19
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 17
- 239000002131 composite material Substances 0.000 description 14
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 12
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 12
- 238000003756 stirring Methods 0.000 description 11
- 239000003085 diluting agent Substances 0.000 description 10
- 239000002923 metal particle Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 9
- 238000001179 sorption measurement Methods 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 229910052697 platinum Inorganic materials 0.000 description 8
- 150000002500 ions Chemical class 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 5
- 238000011156 evaluation Methods 0.000 description 5
- 238000002156 mixing Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000000178 monomer Substances 0.000 description 5
- 238000010992 reflux Methods 0.000 description 5
- 238000007796 conventional method Methods 0.000 description 4
- 238000000366 colloid method Methods 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 239000010948 rhodium Substances 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 238000005453 pelletization Methods 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 2
- 239000012798 spherical particle Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910001111 Fine metal Inorganic materials 0.000 description 1
- 241000264877 Hippospongia communis Species 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- IXSUHTFXKKBBJP-UHFFFAOYSA-L azanide;platinum(2+);dinitrite Chemical compound [NH2-].[NH2-].[Pt+2].[O-]N=O.[O-]N=O IXSUHTFXKKBBJP-UHFFFAOYSA-L 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 239000012876 carrier material Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 208000018459 dissociative disease Diseases 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- QZRHHEURPZONJU-UHFFFAOYSA-N iron(2+) dinitrate nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QZRHHEURPZONJU-UHFFFAOYSA-N 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 150000002940 palladium Chemical class 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000003863 physical function Effects 0.000 description 1
- 150000003058 platinum compounds Chemical class 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Abstract
【課題】より活性の高い排ガス浄化用触媒を提供する。
【解決手段】貴金属微粒子を金属酸化物担体に担持させた後、大気より高い酸素成分の割合の雰囲気において、６００℃よりも高くかつ９００℃よりも低い温度において処理してなる、排ガス浄化用触媒。
【選択図】図２An exhaust gas purifying catalyst having higher activity is provided.
An exhaust gas purifying catalyst comprising a noble metal fine particle supported on a metal oxide carrier and then treated at a temperature higher than 600 ° C. and lower than 900 ° C. in an atmosphere having a higher oxygen component than the atmosphere. .
[Selection] Figure 2
Description
本発明は、排ガス浄化用触媒及びその製造方法に関する。 The present invention relates to an exhaust gas purifying catalyst and a method for producing the same.
自動車等において用いられる排ガス浄化用触媒は、アルミナ、シリカ等の多孔質体を担体とし、この担体に白金、ロジウム等の貴金属を担持させてなり、この貴金属が活性点となって排ガスを浄化している。そしてこの活性点数、すなわち貴金属の比表面積が大きいほど、貴金属の浄化性能が高いことが知られている。 An exhaust gas purification catalyst used in automobiles or the like uses a porous material such as alumina or silica as a carrier, and supports the noble metal such as platinum or rhodium on the carrier, and the noble metal serves as an active point to purify the exhaust gas. ing. It is known that the greater the number of active points, that is, the specific surface area of the noble metal, the higher the purification performance of the noble metal.
担体上に貴金属粒子を担持してなる排ガス浄化用触媒の従来の製造方法としては、多孔質の金属酸化物からなる担体に、ジニトロジアンミン白金等の金属塩溶液を含浸させ、還元雰囲気中で焼成する方法が知られている。このような従来の製造方法では、表面エネルギーの安定化のため、貴金属粒子は球状粒子として生成されやすい。 As a conventional method for producing an exhaust gas purifying catalyst in which noble metal particles are supported on a support, a support made of a porous metal oxide is impregnated with a metal salt solution such as dinitrodiammine platinum and calcined in a reducing atmosphere. How to do is known. In such a conventional manufacturing method, the noble metal particles are easily generated as spherical particles for stabilizing the surface energy.
ところが、粒径がナノオーダーである金属微粒子の物性と機能は、主に形状に左右されることも知られている。例えば、白金表面での一酸化窒素分子の解離反応は、白金表面の形態によって活性が異なり、特に（１００）面の有効性が知られている。 However, it is also known that the physical properties and functions of metal fine particles having a particle size of nano order are mainly influenced by the shape. For example, the dissociation reaction of nitric oxide molecules on the platinum surface has different activity depending on the form of the platinum surface, and the effectiveness of the (100) plane is known.
そこで、触媒反応性として高活性を示すといわれている（１００）面や（１１１）面などの特定の面が成長した、特異な形状である金属微粒子の製造方法が提案されている。 Therefore, a method for producing metal fine particles having a specific shape in which a specific surface such as the (100) surface or the (111) surface is said to exhibit high activity as catalytic reactivity has been proposed.
特許文献１には、Ｐｄイオン存在下、平均粒子径２〜２００ｎｍの第４周期遷移金属元素、第５周期遷移金属元素、白金及び金からなる群より選ばれる少なくとも１種の金属からなる金属粒子を無機系担体物質に担持させることを特徴とする金属粒子担持触媒の製造方法、及びこの方法により製造された、金属粒子の少なくとも一部が多面体状構造を有する多面体状金属粒子が無機系担持物質に担持されてなる金属粒子担持触媒が開示されている。 Patent Document 1 discloses a metal particle made of at least one metal selected from the group consisting of a fourth periodic transition metal element, a fifth periodic transition metal element, platinum, and gold having an average particle diameter of 2 to 200 nm in the presence of Pd ions. A method for producing a metal particle-supported catalyst, characterized in that a polyhedral metal particle having at least a part of a metal particle having a polyhedral structure produced by this method is an inorganic carrier material. A metal particle-supported catalyst supported on a metal is disclosed.
特許文献２には、パラジウム錯体を溶液中で分解することによる、四面体パラジウム微粒子の製造方法が開示されている。特許文献３には、パラジウム塩及び硝酸鉄九水和物の溶液をポリビニルピロリドンを含むアルコールに溶解し、還元することによる金属微粒子の製造方法が開示されている。特許文献４には、白金と、カルボン酸又はカルボン酸塩を含む水溶液から水素還元を行うことによる四面体形状の白金微粒子の製造法が開示されている。特許文献５には、白金化合物と、感温性ポリマーを含む水溶液を所定のｐＨに調整し、還元性ガスを吹き込むことによる、四面体形状の白金微粒子の製造方法が開示されている。 Patent Document 2 discloses a method for producing tetrahedral fine palladium particles by decomposing a palladium complex in a solution. Patent Document 3 discloses a method for producing fine metal particles by dissolving a palladium salt and iron nitrate nonahydrate solution in an alcohol containing polyvinylpyrrolidone and reducing the solution. Patent Document 4 discloses a method for producing tetrahedral platinum fine particles by performing hydrogen reduction from an aqueous solution containing platinum and a carboxylic acid or a carboxylate. Patent Document 5 discloses a method for producing tetrahedral platinum fine particles by adjusting an aqueous solution containing a platinum compound and a thermosensitive polymer to a predetermined pH and blowing a reducing gas.
このような従来の方法では、得られる金属微粒子の多面体の面数が粒子によって大きくばらつき、必ずしも十分な特性が得られないという問題がある。 In such a conventional method, there is a problem that the number of faces of the obtained polyhedral metal fine particles greatly varies depending on the particles, and sufficient characteristics cannot always be obtained.
本発明は上記問題を解決し、貴金属を一方向に成長させて、特に（１００）面を有する直方体の形状を形成し、排ガス浄化性能を大歯に向上させた触媒を提供することを目的とする。 An object of the present invention is to solve the above problems and to provide a catalyst in which a noble metal is grown in one direction to form a rectangular parallelepiped shape having a (100) plane in particular, and the exhaust gas purification performance is greatly improved. To do.
上記問題点を解決するために本発明によれば、貴金属微粒子を金属酸化物担体に担持させた後、大気より高い酸素成分の割合の雰囲気において、６００℃よりも高くかつ９００℃よりも低い温度において処理してなる、排ガス浄化用触媒が提供される。 In order to solve the above problems, according to the present invention, after supporting the noble metal fine particles on the metal oxide support, the temperature is higher than 600 ° C. and lower than 900 ° C. in an atmosphere having a higher oxygen component than the atmosphere. An exhaust gas purifying catalyst is provided.
上記問題点を解決するために２番目の発明によれば、貴金属微粒子を金属酸化物担体に担持させた後、大気より高い酸素成分の割合の雰囲気において、６００℃よりも高くかつ９００℃よりも低い温度において処理することを含む、排ガス浄化用触媒の製造方法が提供される。 In order to solve the above problems, according to the second invention, after the noble metal fine particles are supported on the metal oxide support, in an atmosphere having a higher oxygen component than the atmosphere, the temperature is higher than 600 ° C. and higher than 900 ° C. There is provided a method for producing an exhaust gas purifying catalyst, comprising treating at a low temperature.
本発明の排ガス浄化用触媒は、貴金属微粒子を金属酸化物担体に担持させた後、大気より高い酸素成分の割合の雰囲気において、６００℃よりも高くかつ９００℃よりも低い温度において処理することにより得られるものである。 The exhaust gas purifying catalyst of the present invention is obtained by carrying precious metal fine particles on a metal oxide support and then treating the precious metal particles at a temperature higher than 600 ° C. and lower than 900 ° C. in an atmosphere having a higher oxygen component than the atmosphere. It is obtained.
上記のように、従来の方法により得られる触媒では、図１に示すように、貴金属粒子１は担体２上に球状粒子として生成されやすかった。これに対し、本願発明においては、貴金属を担持させた後、雰囲気制御して処理することにより、図２に示すように、担体２上において貴金属１を直方体の形状に成長させ、活性面を大きくすることにより排ガス浄化性能が大幅に向上する。 As described above, in the catalyst obtained by the conventional method, the noble metal particles 1 were easily generated as spherical particles on the support 2 as shown in FIG. On the other hand, in the present invention, after supporting the noble metal, the atmosphere is controlled and processed to grow the noble metal 1 in the shape of a rectangular parallelepiped on the carrier 2 as shown in FIG. By doing so, the exhaust gas purification performance is greatly improved.
このような本願発明の排ガス浄化用触媒において、触媒担体としては、金属粒子を担持可能な物質であれば制限はなく、一般的に用いられている、Ｓｉ、Ａｌ、Ｃ、Ｔｉ、Ｚｒ、Ｃｅ等から選ばれる１種以上の酸化物を用いることができる。またこの担体の形状も特に制限はなく、粉末、ビーズ、ペレット、ハニカム等の一般に用いられている形状のものを使用することができる。 In such an exhaust gas purifying catalyst of the present invention, the catalyst carrier is not limited as long as it is a substance capable of supporting metal particles, and commonly used Si, Al, C, Ti, Zr, Ce One or more oxides selected from the above can be used. Also, the shape of the carrier is not particularly limited, and a generally used shape such as powder, beads, pellets, and honeycombs can be used.
貴金属としては、排ガス浄化用触媒において一般に用いられている白金（Ｐｔ）、パラジウム（Ｐｄ）、ロジウム（Ｒｈ）、金（Ａｕ）、及びイリジウム（Ｉｒ）からなる群から選ばれる１以上の貴金属を用いることができる。 As the noble metal, one or more noble metals selected from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), gold (Au), and iridium (Ir) generally used in exhaust gas purification catalysts are used. Can be used.
この貴金属は粒径が１．０ｎｍより大きいことが好ましく、また３．０ｎｍ未満であることが好ましい。なお、この粒径はＣＯ吸着量評価により測定した粒径を意味する。すなわち、触媒０．２ｇを４００℃で２０分酸化し、還元処理後、０℃でＣＯを吸着させ、このＣＯ吸着量から計算して算出した粒径である。この貴金属粒子の調製法は特に制限はなく、一般に用いられている方法、例えばコロイド法等により調製することができる。 The noble metal preferably has a particle size of greater than 1.0 nm and preferably less than 3.0 nm. In addition, this particle size means the particle size measured by CO adsorption amount evaluation. That is, the particle size was calculated by oxidizing 0.2 g of the catalyst at 400 ° C. for 20 minutes, adsorbing CO at 0 ° C. after the reduction treatment, and calculating from this CO adsorption amount. The method for preparing the noble metal particles is not particularly limited, and can be prepared by a commonly used method such as a colloid method.
担体への貴金属の担持法も特に制限はなく、一般に用いられている浸漬法等を用いることができる。また、担体への貴金属の担持量にも特に制限はないが、一般には貴金属担持量は触媒全重量に対して0.01〜50wt％、好ましくは0.05〜40wt％である。 The method for supporting the noble metal on the carrier is not particularly limited, and a commonly used dipping method or the like can be used. The amount of noble metal supported on the carrier is not particularly limited, but generally the amount of noble metal supported is 0.01 to 50 wt%, preferably 0.05 to 40 wt%, based on the total weight of the catalyst.
こうして貴金属微粒子を担体に担持させた後、本発明においては、酸素成分の割合が大気よりも高い雰囲気、好ましくは酸素のみの雰囲気において、６００℃よりも高くかつ９００℃よりも低い温度において処理する。このような処理を行うことにより、担体上の貴金属微粒子は一方向に成長し、直方体状の形状を形成することにより比表面積が増大し、高活性を示すことになる。すなわち、本発明の排ガス浄化用触媒は、担体上に担持された貴金属粒子が直方体状の形状を呈するものである。 After the noble metal fine particles are supported on the carrier in this way, in the present invention, the treatment is performed at a temperature higher than 600 ° C. and lower than 900 ° C. in an atmosphere in which the proportion of oxygen component is higher than the atmosphere, preferably an atmosphere containing only oxygen. . By performing such treatment, the noble metal fine particles on the support grow in one direction, and by forming a rectangular parallelepiped shape, the specific surface area is increased and high activity is exhibited. That is, the exhaust gas purifying catalyst of the present invention is such that the noble metal particles supported on the carrier have a rectangular parallelepiped shape.
実施例１
まず、コロイド法を用いて、以下のようにしてＰｄ微粒子を調製した。Ｐｄ総量が4.50×10-3molの塩化Ｐｄ溶液にイオン交換水を加えて撹拌した、総量300gのＰｄ希釈液を調製した。またモノマーユニット換算で2.25×10-2mol、Ｐｄ総量の５倍となるポリビニルピロリドン（ＰＶＰ）2.52gにイオン交換水300gを加え、撹拌し、完全に溶解させた均一なＰＶＰ溶液を調製した。次いで、このＰＶＰ溶液にＰｄ希釈液をゆっくり滴下して混合し、室温において１時間撹拌した。次いで、イオン交換水とメタノールの混合比率が80：20（wt％）となるようにメタノールを加えて30分程度撹拌した。さらに、この溶液を加熱還流し、Ｐｄイオンを還元することによって粒径3.0nm程度のＰｄ微粒子溶液を得た。
Example 1
First, using a colloid method, Pd fine particles were prepared as follows. A Pd diluent having a total amount of 300 g was prepared by adding ion-exchanged water to a Pd chloride solution having a total amount of Pd of 4.50 × 10 −3 mol and stirring. Moreover, 300 g of ion-exchanged water was added to 2.52 g of polyvinylpyrrolidone (PVP), which was 2.25 × 10 −2 mol in terms of monomer units and 5 times the total amount of Pd, and stirred to prepare a homogeneous PVP solution completely dissolved. Next, a Pd diluent was slowly added dropwise to the PVP solution and mixed, followed by stirring at room temperature for 1 hour. Next, methanol was added so that the mixing ratio of ion-exchanged water and methanol was 80:20 (wt%), and the mixture was stirred for about 30 minutes. Further, this solution was heated to reflux to reduce Pd ions to obtain a Pd fine particle solution having a particle size of about 3.0 nm.
こうして調製したＰｄ微粒子溶液を、重量にして６倍の蒸留水に分散させた30gのＣｅＯ2系複合酸化物の粉末に、Ｐｄが粉末に対して0.5wt％となるように添加し、１時間撹拌した。さらに、120℃で水分を蒸発させ、450℃で２時間焼成し、乳鉢中で粉砕し、得られた粉末をペレット化することによってＰｄ／ＣｅＯ2系複合酸化物からなる排ガス浄化用触媒を調製した。 The Pd fine particle solution thus prepared was added to 30 g of CeO 2 composite oxide powder dispersed in 6 times by weight of distilled water so that Pd was 0.5 wt% with respect to the powder. Stir. Furthermore, a catalyst for exhaust gas purification comprising a Pd / CeO 2 composite oxide is prepared by evaporating water at 120 ° C., calcining at 450 ° C. for 2 hours, pulverizing in a mortar, and pelletizing the obtained powder. did.
さらに得られたＰｄ／ＣｅＯ2系複合酸化物を１Ｐａの酸素中で700℃において１時間処理を行った。この処理前のＰｄ／ＣｅＯ2系複合酸化物と処理を行ったＰｄ／ＣｅＯ2系複合酸化物について、透過型電子顕微鏡（ＴＥＭ）観察を行った。結果を図３に示す。 Further, the obtained Pd / CeO 2 composite oxide was treated at 700 ° C. for 1 hour in 1 Pa of oxygen. The Pd / CeO 2 composite oxide before this treatment and the treated Pd / CeO 2 composite oxide were observed with a transmission electron microscope (TEM). The results are shown in FIG.
処理前のＰｄ／ＣｅＯ2系複合酸化物（図３ａ）においては、Ｐｄが球状となっているが、処理後のＰｄ／ＣｅＯ2系複合酸化物（図３ｂ）においては、一方向に成長し、（１００）面を有する直方体の形状を形成していた。 In the Pd / CeO 2 composite oxide before treatment (FIG. 3a), Pd is spherical, but in the Pd / CeO 2 composite oxide after treatment (FIG. 3b), it grows in one direction. , A rectangular parallelepiped shape having a (100) plane.
上記の処理前のＰｄ／ＣｅＯ2系複合酸化物と処理を行ったＰｄ／ＣｅＯ2系複合酸化物について、図４に示す態様で、以下の条件においてＣＯパルス法によりＣＯ吸着量とＴＨＣの浄化性能を評価した。
・ＣＯ吸着量評価条件
容器に0.2gの触媒を入れ、400℃で20分酸化させ、還元処理後、０℃でＣＯを吸着させた。
・浄化性能評価ガス条件
触媒量：3.0g
ガス総流量：15Ｌ／min
ガス組成：Ｃ3Ｈ6 1000ppm、ＣＯ 6500ppm、ＮＯ 1500ppm、Ｏ2 7000ppm、ＣＯ2 10％、Ｈ2Ｏ 無し、Ｎ2 残余
温度条件：降温600→100℃、20℃／min
For the above pretreatment Pd / CeO 2 composite oxide and processes the Pd / CeO 2 composite oxide was carried out, in the manner shown in FIG. 4, the purification of CO adsorption amount and THC by CO pulse method under the following conditions Performance was evaluated.
-Conditions for evaluating CO adsorption amount 0.2 g of catalyst was placed in a container, oxidized at 400 ° C for 20 minutes, and after reduction treatment, CO was adsorbed at 0 ° C.
・ Purification performance evaluation gas conditions Catalyst amount: 3.0 g
Total gas flow: 15L / min
Gas composition: C 3 H 6 1000 ppm, CO 6500 ppm, NO 1500 ppm, O 2 7000 ppm, CO 2 10%, H 2 O none, N 2 residual Temperature conditions: Temperature drop 600 → 100 ° C., 20 ° C./min
以上の結果を図５及び図６に示す。図５に示す結果より、雰囲気制御した処理を行うことにより、触媒１ｇあたりのＣＯ吸着量が向上する、すなわち、Ｐｄの比表面積が向上していることが確認された。これは、図３に示すＴＥＭ像のように、Ｐｄ粒子が担体上で一方向に成長し、直方体の形状を形成したためであると考えられる。また、図６に示す結果より、雰囲気制御した処理を行うことにより、Ｐｄの比表面積の向上によって予想される効果以上に浄化性能が大幅に向上した。これは、直方体を形成することにより、高活性を示す（１００）面を有するようになったためであると考えられる。 The above results are shown in FIGS. From the results shown in FIG. 5, it was confirmed that the amount of CO adsorption per gram of the catalyst was improved, that is, the specific surface area of Pd was improved by performing the atmosphere-controlled treatment. This is presumably because the Pd particles grew in one direction on the carrier and formed a rectangular parallelepiped shape as in the TEM image shown in FIG. Further, from the results shown in FIG. 6, the purification performance was greatly improved by performing the atmosphere-controlled process, more than the effect expected by the improvement of the specific surface area of Pd. This is presumably because the formation of a rectangular parallelepiped has a (100) plane exhibiting high activity.
実施例２
コロイド法を用いて、以下のようにして実施例１とは粒径の異なるＰｄ微粒子を合成した。
(1)Ｐｄ総量が4.50×10-3molの塩化Ｐｄ溶液にイオン交換水を加えて撹拌した、総量300gのＰｄ希釈液を調製した。またモノマーユニット換算で2.25×10-2mol、Ｐｄ総量の５倍となるポリビニルピロリドン（ＰＶＰ）2.52gにイオン交換水300gを加え、撹拌し、完全に溶解させた均一なＰＶＰ溶液を調製した。次いで、このＰＶＰ溶液にＰｄ希釈液をゆっくり滴下して混合し、室温において１時間撹拌した。次いで、イオン交換水とエタノールの混合比率が80：20（wt％）となるようにエタノールを加えて30分程度撹拌した。さらに、この溶液を加熱還流し、Ｐｄイオンを還元することによって粒径2.0nm程度のＰｄ微粒子溶液を得た。
Example 2
Using the colloid method, Pd fine particles having a particle diameter different from that of Example 1 were synthesized as follows.
(1) A Pd diluent having a total amount of 300 g was prepared by adding ion-exchanged water to a Pd chloride solution having a total Pd amount of 4.50 × 10 −3 mol and stirring. Moreover, 300 g of ion-exchanged water was added to 2.52 g of polyvinylpyrrolidone (PVP), which was 2.25 × 10 −2 mol in terms of monomer units and 5 times the total amount of Pd, and stirred to prepare a homogeneous PVP solution completely dissolved. Next, a Pd diluent was slowly added dropwise to the PVP solution and mixed, followed by stirring at room temperature for 1 hour. Next, ethanol was added so that the mixing ratio of ion-exchanged water and ethanol was 80:20 (wt%), and the mixture was stirred for about 30 minutes. Further, this solution was heated to reflux to reduce Pd ions to obtain a Pd fine particle solution having a particle size of about 2.0 nm.
(2)Ｐｄ総量が4.50×10-3molの塩化Ｐｄ溶液にイオン交換水を加えて撹拌した、総量300gのＰｄ希釈液を調製した。またモノマーユニット換算で2.25×10-2mol、Ｐｄ総量の５倍となるポリビニルピロリドン（ＰＶＰ）2.52gにイオン交換水300gを加え、撹拌し、完全に溶解させた均一なＰＶＰ溶液を調製した。次いで、このＰＶＰ溶液にＰｄ希釈液をゆっくり滴下して混合し、室温において１時間撹拌した。次いで、イオン交換水と１−プロパノールの混合比率が80：20（wt％）となるように１−プロパノールを加えて30分程度撹拌した。さらに、この溶液を加熱還流し、Ｐｄイオンを還元することによって粒径1.5nm程度のＰｄ微粒子溶液を得た。 (2) A Pd diluent having a total amount of 300 g was prepared by adding ion-exchanged water to a Pd chloride solution having a total Pd amount of 4.50 × 10 −3 mol and stirring. Moreover, 300 g of ion-exchanged water was added to 2.52 g of polyvinylpyrrolidone (PVP), which was 2.25 × 10 −2 mol in terms of monomer units and 5 times the total amount of Pd, and stirred to prepare a homogeneous PVP solution completely dissolved. Next, a Pd diluent was slowly added dropwise to the PVP solution and mixed, followed by stirring at room temperature for 1 hour. Subsequently, 1-propanol was added and stirred for about 30 minutes so that the mixing ratio of ion-exchanged water and 1-propanol was 80:20 (wt%). Further, this solution was heated to reflux to reduce Pd ions to obtain a Pd fine particle solution having a particle size of about 1.5 nm.
(3)Ｐｄ総量が4.50×10-3molの塩化Ｐｄ溶液にイオン交換水を加えて撹拌した、総量300gのＰｄ希釈液を調製した。またモノマーユニット換算で2.25×10-2mol、Ｐｄ総量の５倍となるポリビニルピロリドン（ＰＶＰ）2.52gにイオン交換水300gを加え、撹拌し、完全に溶解させた均一なＰＶＰ溶液を調製した。次いで、このＰＶＰ溶液にＰｄ希釈液をゆっくり滴下して混合し、室温において１時間撹拌した。次いで、イオン交換水と１−プロパノールの混合比率が80：20（wt％）となるように１−プロパノールを加えて30分程度撹拌した。さらに、この溶液を加熱還流し、Ｐｄイオンを還元することによって粒径5.0nm程度のＰｄ微粒子溶液を得た。 (3) A Pd diluent having a total amount of 300 g was prepared by adding ion-exchanged water to a Pd chloride solution having a total Pd amount of 4.50 × 10 −3 mol and stirring. Moreover, 300 g of ion-exchanged water was added to 2.52 g of polyvinylpyrrolidone (PVP), which was 2.25 × 10 −2 mol in terms of monomer units and 5 times the total amount of Pd, and stirred to prepare a homogeneous PVP solution completely dissolved. Next, a Pd diluent was slowly added dropwise to the PVP solution and mixed, followed by stirring at room temperature for 1 hour. Subsequently, 1-propanol was added and stirred for about 30 minutes so that the mixing ratio of ion-exchanged water and 1-propanol was 80:20 (wt%). Further, this solution was heated to reflux to reduce Pd ions to obtain a Pd fine particle solution having a particle size of about 5.0 nm.
(4)Ｐｄ総量が4.50×10-3molの塩化Ｐｄ溶液にイオン交換水を加えて撹拌した、総量300gのＰｄ希釈液を調製した。またモノマーユニット換算で2.25×10-2mol、Ｐｄ総量の５倍となるポリビニルピロリドン（ＰＶＰ）2.52gにイオン交換水300gを加え、撹拌し、完全に溶解させた均一なＰＶＰ溶液を調製した。次いで、このＰＶＰ溶液にＰｄ希釈液をゆっくり滴下して混合し、室温において１時間撹拌した。次いで、イオン交換水とメタノールの混合比率が80：20（wt％）となるようにメタノールを加えて30分程度撹拌した。さらに、この溶液を加熱還流し、Ｐｄイオンを還元することによって粒径8.0nm程度のＰｄ微粒子溶液を得た。 (4) A Pd diluent having a total amount of 300 g was prepared by adding ion-exchanged water to a Pd chloride solution having a total amount of Pd of 4.50 × 10 −3 mol and stirring. Moreover, 300 g of ion-exchanged water was added to 2.52 g of polyvinylpyrrolidone (PVP), which was 2.25 × 10 −2 mol in terms of monomer units and 5 times the total amount of Pd, and stirred to prepare a homogeneous PVP solution completely dissolved. Next, a Pd diluent was slowly added dropwise to the PVP solution and mixed, followed by stirring at room temperature for 1 hour. Next, methanol was added so that the mixing ratio of ion-exchanged water and methanol was 80:20 (wt%), and the mixture was stirred for about 30 minutes. Further, this solution was heated to reflux to reduce Pd ions to obtain a Pd fine particle solution having a particle size of about 8.0 nm.
こうして合成した各種Ｐｄ微粒子溶液と硝酸Ｐｄ（粒径0.8nm程度の微粒子）を、重量にして６倍の蒸留水に分散させた30gのＣｅＯ2系複合酸化物の粉末に、Ｐｄが粉末に対して0.5wt％となるように添加し、１時間撹拌した。さらに、120℃で水分を蒸発させ、450℃で２時間焼成し、乳鉢中で粉砕し、得られた粉末をペレット化することによってＰｄ／ＣｅＯ2系複合酸化物からなる排ガス浄化用触媒を調製した。さらに、得られた各種粒径のＰｄ／ＣｅＯ2系複合酸化物の一部を、１Ｐａの酸素中で700℃で１時間処理を行った。 Various Pd fine particle solutions thus synthesized and Pd nitrate (fine particles having a particle diameter of about 0.8 nm) were dispersed in distilled water with a weight of 6 times in 30 g of CeO 2 -based composite oxide powder. The mixture was added to 0.5 wt% and stirred for 1 hour. Furthermore, a catalyst for exhaust gas purification comprising a Pd / CeO 2 composite oxide is prepared by evaporating water at 120 ° C., calcining at 450 ° C. for 2 hours, pulverizing in a mortar, and pelletizing the obtained powder. did. Furthermore, a part of the obtained Pd / CeO 2 composite oxide having various particle diameters was treated at 700 ° C. for 1 hour in 1 Pa of oxygen.
これらの触媒について、実施例１と同様にしてＣＯパルス法によるＣＯ吸着量とＴＨＣの浄化性能を評価し、結果を図７及び図８に示す。 For these catalysts, the CO adsorption amount and THC purification performance by the CO pulse method were evaluated in the same manner as in Example 1, and the results are shown in FIGS.
図に示すように、担体に担持させる前のＰｄの粒径が2.0nm以上において、雰囲気制御して処理を行うと比表面積が増加し、浄化性能も大幅に向上した。これは、粒径が2.0nm以上の貴金属が担持されていると、貴金属が一方向に成長し、直方体を形成して、高活性を示す（１００）面を有するようになったためであると考えられる。なお、浄化性能が単純にＰｄの比表面積によらず、２nm付近で高活性を示すことについては、単体がＣｅＯ2系複合酸化物であるため、0.8nmよりも小さい領域では担体との相互作用によりＰｄが酸化物に近い状態で存在し、低活性を示すため、３nmより大きい領域では活性点が減少し、低活性を示すためであると考えられる。 As shown in the figure, when the Pd particle size before being supported on the carrier was 2.0 nm or more, the treatment was performed under atmosphere control, the specific surface area was increased and the purification performance was greatly improved. This is considered to be because when a noble metal having a particle size of 2.0 nm or more is supported, the noble metal grows in one direction, forms a rectangular parallelepiped, and has a (100) surface exhibiting high activity. It is done. Note that the purification performance simply shows high activity near 2 nm regardless of the specific surface area of Pd. Since the simple substance is a CeO 2 -based composite oxide, the interaction with the carrier is smaller than 0.8 nm. This is probably because Pd exists in a state close to an oxide and exhibits low activity, so that the active point decreases in a region larger than 3 nm and exhibits low activity.
実施例３
実施例１で合成した、粒径が3.0nm程度のＰｄ微粒子を用いたＰｄ／ＣｅＯ2系複合酸化物からなる排ガス浄化用触媒の一部を、以下の条件で雰囲気制御した処理を行った。
Example 3
A part of the exhaust gas-purifying catalyst composed of Pd / CeO 2 -based composite oxide using Pd fine particles having a particle size of about 3.0 nm synthesized in Example 1 was subjected to a treatment in which the atmosphere was controlled under the following conditions.
上記の排ガス浄化用触媒の浄化性能について、実施例１と同様にして評価を行った。結果を図９に示す。 The purification performance of the exhaust gas purification catalyst was evaluated in the same manner as in Example 1. The results are shown in FIG.
図９に示す浄化性能の結果より、サンプルＮｏ．１に対してＮｏ．３、４、及び５が高活性を示しており、完全に酸素雰囲気である方が好ましく、またサンプルＮｏ．７に対してサンプルＮｏ．９、１０及び１１が高活性を示しており、処理温度が６００℃よりも高く、９００℃より低いことが好ましいと考えられる。 From the purification performance results shown in FIG. No. 1 3, 4, and 5 show high activity, and it is preferable to have a completely oxygen atmosphere. For sample 7, sample no. 9, 10 and 11 show high activity, and it is considered that the treatment temperature is preferably higher than 600 ° C and lower than 900 ° C.
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| JP2014108392A (en) * | 2012-12-03 | 2014-06-12 | Toyota Motor Corp | Method of manufacturing catalyst for removing exhaust gas and catalyst obtained by the manufacturing method |
| CN104822453A (en) * | 2012-12-03 | 2015-08-05 | 丰田自动车株式会社 | Method for producing catalyst for exhaust gas removal, and catalyst obtained by said production method |
| EP2926900A4 (en) * | 2012-12-03 | 2016-01-06 | Toyota Motor Co Ltd | PROCESS FOR PRODUCING A CATALYST FOR EXHAUST GAS DISPOSAL AND CATALYST OBTAINED BY SAID PRODUCTION PROCESS |
| RU2604537C1 (en) * | 2012-12-03 | 2016-12-10 | Тойота Дзидося Кабусики Кайся | Method of producing catalyst for cleaning exhaust gases and catalyst produced by said method |
| US9889432B2 (en) | 2012-12-03 | 2018-02-13 | Toyota Jidosha Kabushiki Kaisha | Method for producing catalyst for exhaust gas removal and catalyst obtained by the production method |
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