JP2012187495A - Catalyst, and method for producing the same - Google Patents
Catalyst, and method for producing the same Download PDFInfo
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Abstract
Description
本発明の実施の形態は、炭化水素系燃料あるいはアルコール系燃料改質用、もしくはカーボン合成用触媒、及びその製造方法に関するものである。
Embodiments of the present invention relate to a hydrocarbon fuel or alcohol fuel reforming or carbon synthesis catalyst, and a method for producing the same.
ニッケルや銅などの金属微粒子からなる触媒は、炭化水素系もしくはアルコール系燃料と水蒸気を一緒に加熱・反応させて、工業的に有用な水素を製造することができる。また、ガス化させた炭化水素系燃料あるいはアルコール系燃料からは強化材、導電材として有用なカーボンナノ繊維を作ることも可能である。 Catalysts made of fine metal particles such as nickel and copper can produce industrially useful hydrogen by heating and reacting a hydrocarbon or alcohol fuel and steam together. In addition, carbon nanofibers useful as reinforcing materials and conductive materials can be made from gasified hydrocarbon fuels or alcohol fuels.
一般に、これらに用いる金属微粒子は、基板上や多孔質に形成したセラミックス上に溶液法あるいは気相法などを用いて作られる。しかし、このようにして作製した金属微粒子は、使用する温度や反応の過程で隣接する粒子同士の凝集や焼結を起こしやすいことが知られている。 In general, the metal fine particles used for these are produced on a substrate or a porous ceramic by using a solution method or a gas phase method. However, it is known that the metal fine particles produced in this way are likely to cause aggregation and sintering of adjacent particles during the temperature and reaction process.
一方、還元されやすい金属を含む酸化物と還元されにくい金属を含む酸化物の複合体から成る焼結体を還元することによって、還元雰囲気下でより不安定な金属成分を焼結体上に析出させ、触媒とする方法も提案されている。この方法によれば、酸化物焼結体上に金属微粒子を高密度に分散・形成し、しかも基材である酸化物焼結体と結合性をもって固定化させることができるため、高い触媒性能と熱的な安定性が期待される。 On the other hand, by reducing a sintered body composed of a composite of an oxide containing a metal that is easily reduced and an oxide containing a metal that is difficult to reduce, a more unstable metal component is deposited on the sintered body in a reducing atmosphere. A method of using the catalyst as a catalyst has also been proposed. According to this method, the fine metal particles can be dispersed and formed at a high density on the oxide sintered body, and can be fixed with a binding property to the oxide sintered body as a base material. Thermal stability is expected.
しかし、この方法による金属微粒子の析出は主に複合酸化物焼結体を構成する複合酸化物の粒子と粒子の境界、いわゆる粒界部（粒界）にて優先的に起こるため、粒界に金属微粒子の析出が集中する。その結果、粒界部において大きなサイズの金属粒子が存在することになり、不均一な組織となっていた。一つ一つの粒子を大きくさせて、粒界となる部分を減らすことができれば、複合酸化物焼結体の粒子上に均一でそろった粒径の金属微粒子からなる組織が形成でき、効果が期待される。一般的に、粒子の粒子径を大きくするには、高温で焼結するか、あるいは長時間焼結するといった方法が考えられるが、これらの方法ではコストも高くなり、また実際にその効果は小さいものであった。
However, precipitation of metal fine particles by this method mainly occurs at the boundary between the particles of the composite oxide constituting the composite oxide sintered body, that is, the so-called grain boundary portion (grain boundary). Precipitation of metal fine particles concentrates. As a result, metal particles having a large size are present in the grain boundary portion, resulting in a non-uniform structure. If each particle can be enlarged and the number of grain boundaries can be reduced, a structure consisting of metal particles with uniform and uniform particle size can be formed on the particles of the composite oxide sintered body, and the effect is expected. Is done. In general, to increase the particle size of the particles, methods such as sintering at a high temperature or sintering for a long time can be considered, but these methods also increase the cost and actually have little effect. It was a thing.
この発明の実施の形態によれば、過大なエネルギーを投入することなく複合酸化物の粒子の粒子径を大径化することを可能にする。
According to the embodiment of the present invention, it is possible to increase the particle size of the composite oxide particles without applying excessive energy.
第１の実施態様に係る触媒は、ニッケル、コバルト、鉄、銅より選ばれる少なくとも一種と、アルミニウム、マグネシウム、クロムより選ばれる少なくとも一種とを含む複合酸化物焼結体を構成する前記複合酸化物の粒子の表面にニッケル、コバルト、鉄、銅より選ばれる少なくとも一種からなる金属微粒子を具備し、前記複合酸化物焼結体がバナジウム成分を含有していることを特徴とする。
第２の実施形態に係る触媒の製造方法は、ニッケル、コバルト、鉄、銅より選ばれる少なくとも一種と、アルミニウム、マグネシウム、クロムより選ばれる少なくとも一種と、バナジウムを含む化合物を混合する工程と、前記混合物を加熱反応処理して複合酸化物とする工程と、前記複合酸化物を還元処理しニッケル、コバルト、鉄、銅の少なくとも一種を含む金属微粒子を前記複合酸化物の表面に析出せしめる工程と、を有する。
The catalyst according to the first embodiment includes the composite oxide comprising the composite oxide sintered body including at least one selected from nickel, cobalt, iron, and copper and at least one selected from aluminum, magnesium, and chromium. The surface of the particles comprises metal fine particles made of at least one selected from nickel, cobalt, iron, and copper, and the composite oxide sintered body contains a vanadium component.
The method for producing a catalyst according to the second embodiment includes a step of mixing a compound containing vanadium with at least one selected from nickel, cobalt, iron, and copper, at least one selected from aluminum, magnesium, and chromium; A step of subjecting the mixture to a thermal reaction treatment to form a composite oxide; a step of reducing the composite oxide to deposit metal fine particles containing at least one of nickel, cobalt, iron, and copper on the surface of the composite oxide; Have
［触媒］
本実施形態による触媒は、複合酸化物焼結体を構成する複合酸化物の粒子の表面に金属微粒子を具備したもので、前記複合酸化物焼結体の内部にバナジウム成分を含有してなることを特徴としている。
[catalyst]
The catalyst according to the present embodiment comprises metal oxide particles on the surface of the composite oxide particles constituting the composite oxide sintered body, and contains a vanadium component inside the composite oxide sintered body. It is characterized by.
前記複合酸化物焼結体は、還元性雰囲気下で還元されやすい金属と還元され難い金属により構成される酸化物固溶型、もしくはスピネル型の複合酸化物を主成分とする。還元されやすい金属の例としては、ニッケル、コバルト、鉄、銅などであり、還元され難い金属の例としては、アルミニウム、マグネシウム、クロムなどである。これらは複数組み合わされても構わない。また、担持される金属微粒子は、ニッケル、コバルト、鉄、銅およびこれらの組み合わせとなる。 The composite oxide sintered body is mainly composed of an oxide solid solution type or spinel type composite oxide composed of a metal that is easily reduced and a metal that is not easily reduced in a reducing atmosphere. Examples of metals that are easily reduced include nickel, cobalt, iron, and copper, and examples of metals that are difficult to reduce include aluminum, magnesium, and chromium. A plurality of these may be combined. The supported metal fine particles are nickel, cobalt, iron, copper, and combinations thereof.
前記複合酸化物焼結体の内部に存在するバナジウム成分は、前記複合酸化物の前駆体を焼結する際に、それを構成する複合酸化物の粒子の粒成長を促進し、焼結体を緻密化させる。バナジウム成分を添加しない前記複合酸化物の粒子の平均粒径がおよそ１μｍ程度であるのに対し、バナジウム成分を添加した場合では、前記複合酸化物の粒径は数１０μｍ〜数１００μｍにまで達する。 The vanadium component present inside the composite oxide sintered body promotes the grain growth of the composite oxide particles constituting the composite oxide precursor when the precursor of the composite oxide is sintered. Densify. The average particle size of the composite oxide particles to which no vanadium component is added is about 1 μm, whereas when the vanadium component is added, the composite oxide has a particle size of several tens to several hundreds of μm.
バナジウム成分は前記複合酸化物焼結体の内部に存在していればよいが、それらが特に複合酸化物の粒子と粒子の間の粒界部近傍に偏在していても構わない。バナジウムはマグネシウム酸化物中にほとんど固溶しないと考えられるため、大部分は粒界部にとどまっているものと考えられる。 Vanadium components may be present in the composite oxide sintered body, but they may be unevenly distributed, particularly in the vicinity of the grain boundary portion between the composite oxide particles. Since vanadium is considered to hardly dissolve in the magnesium oxide, most of it is considered to remain at the grain boundary.
また、含有されるバナジウム成分は、元素量で０．０１モル％以上０．５モル％以下の量で含有されることが好ましい。元素量０．０１モル％より少ない場合には複合酸化物の粒子を大径化できない恐れがある。また、０．５モル％より大きくなると複合酸化物の強度を低下させる恐れがある。また、バナジウムは希少な元素であるため、その使用量は極力少なくするのが好ましい。
本実施形態により作製される触媒では、金属微粒子は複合酸化物の粒子の内部には析出しない。金属微粒子はすべて複合酸化物の粒子の表面部に析出する。したがって、外から見ると、この表面部における分散密度（表面部の単位面積当たりの金属粒子数）が高くなる。バナジウムを添加した触媒の場合、金属粒子の分散密度は、金属成分の添加量や析出させる金属粒子のサイズにもよるが、例えば１０個／μｍ２〜５，０００個／μｍ２ほどである。これによって、金属粒子の触媒効果をより効果的に発揮させることができる
The vanadium component contained is preferably contained in an amount of 0.01 mol% or more and 0.5 mol% or less in terms of elemental amount. If the elemental amount is less than 0.01 mol%, the composite oxide particles may not be enlarged. On the other hand, if it exceeds 0.5 mol%, the strength of the composite oxide may be reduced. Further, since vanadium is a rare element, it is preferable to reduce the amount used.
In the catalyst produced according to the present embodiment, the metal fine particles are not precipitated inside the composite oxide particles. All metal fine particles are deposited on the surface of the composite oxide particles. Therefore, when viewed from the outside, the dispersion density in the surface portion (the number of metal particles per unit area of the surface portion) increases. For catalyst added vanadium, dispersion density of the metal particles, depending on the size of the metal particles to be added the amount or deposition of the metal component, for example, at about 10 / [mu] m 2 to 5,000 pieces / [mu] m 2. As a result, the catalytic effect of the metal particles can be more effectively exhibited.
［触媒の製造方法］
次に、触媒材料の製造方法の実施形態について説明する。
まず、ニッケル、コバルト、鉄、銅より選ばれる少なくとも一種を含む酸化物粉末と、アルミニウム、マグネシウム、クロムより選ばれる少なくとも一種を含む酸化物粉末に、バナジウム成分を含有する酸化物粉末を混合する。この場合、これら成分はいずれも酸化物粉末である必要はなく、硝酸塩や硫酸塩などを用いても構わない。
この際、複合酸化物の主成分が、金属固溶体酸化物もしくはスピネル型複合酸化物となるような組み合わせを選択する。その理由は次の通りである。単に複合されただけの酸化物である場合、複合酸化物中に、例えば酸化ニッケルや酸化コバルト、酸化鉄、酸化銅などの成分をもつ粒子が含まれることになる。これら粒子のサイズは出発原料にもよるが小さくてもせいぜい数１００ｎｍ程度である。これら酸化物は還元雰囲気中、３００〜５００℃で容易に還元されて全体としては金属と酸化物の複合体となるが、両者粒子が混在した形の組織になる。これに対し、金属固溶体もしくはスピネル型複合酸化物は構成する全ての粒子が一様な組成をもつ複合酸化物焼結体である。これを還元処理したものは、複合酸化物の粒子の中から金属成分が滲み出し、結果として複合酸化物の粒子の表面に数ｎｍ〜数１０ｎｍサイズの金属の微粒子を形成することができる。この際、還元による析出温度も高いのが特徴である。
[Method for producing catalyst]
Next, an embodiment of a method for producing a catalyst material will be described.
First, an oxide powder containing a vanadium component is mixed with an oxide powder containing at least one selected from nickel, cobalt, iron, and copper and an oxide powder containing at least one selected from aluminum, magnesium, and chromium. In this case, all of these components do not need to be oxide powders, and nitrates, sulfates, and the like may be used.
At this time, a combination is selected such that the main component of the complex oxide is a metal solid solution oxide or a spinel complex oxide. The reason is as follows. When the oxide is simply combined, particles having components such as nickel oxide, cobalt oxide, iron oxide, and copper oxide are included in the composite oxide. Although the size of these particles depends on the starting material, it is at most about several hundred nm even if it is small. These oxides are easily reduced at 300 to 500 ° C. in a reducing atmosphere to form a composite of metal and oxide as a whole, but have a structure in which both particles are mixed. On the other hand, a metal solid solution or a spinel type composite oxide is a composite oxide sintered body in which all the constituent particles have a uniform composition. In the case of this, a metal component oozes out from the composite oxide particles, and as a result, metal fine particles having a size of several nanometers to several tens of nanometers can be formed on the surface of the composite oxide particles. In this case, the precipitation temperature by reduction is also high.
次いで、前記混合粉末を所望の形に成形し、焼結することにより、複合酸化物の粒子が複数集まって構成される複合酸化物焼結体とする。
前記混合粉末の平均粒径は、０．１〜１０μｍの範囲が好ましい。ここでいう平均粒径とはレーザー回折法による粒度分布測定における平均の粒径をいう。平均粒径がこの範囲を上回った場合、焼結体は、均一な金属固溶体酸化物もしくはスピネル型複合酸化物を形成することが困難になる。一方、平均粒径がこの範囲を下回った場合、その取扱いが困難になり作業性が低下する。
焼結の条件は、１１００〜１５００℃で、１〜５時間加熱することによって行うことができる。それぞれの条件が上記範囲を下回った場合、焼結が不十分で、均一な金属固溶体酸化物もしくはスピネル型複合酸化物を形成することが困難になる。また、上記条件範囲を上回る条件で加熱しても、生成する焼結体の特性の向上を期待することはできず、エネルギーの損失につながる。
Next, the mixed powder is formed into a desired shape and sintered to obtain a composite oxide sintered body composed of a plurality of composite oxide particles.
The average particle diameter of the mixed powder is preferably in the range of 0.1 to 10 μm. The average particle size here means an average particle size in the particle size distribution measurement by the laser diffraction method. When the average particle size exceeds this range, it becomes difficult for the sintered body to form a uniform metal solid solution oxide or spinel type complex oxide. On the other hand, when the average particle size is below this range, handling becomes difficult and workability is lowered.
Sintering can be performed by heating at 1100 to 1500 ° C. for 1 to 5 hours. When each condition falls below the above range, sintering is insufficient, and it becomes difficult to form a uniform metal solid solution oxide or spinel type complex oxide. Moreover, even if it heats on the conditions beyond the said condition range, the improvement of the characteristic of the sintered compact to produce | generate cannot be expected, but it leads to the loss of energy.
前記全固溶体酸化物を形成する組合せとしては、ＮｉＯ−ＭｇＯ、ＣｏＯ−ＭｇＯ、ＦｅＯ−ＭｇＯ、ＣｕＯ−ＭｇＯ
などの原料の組合せがあげられる。
また、前記スピネル型複合酸化物を形成する組合せとしては、ＮｉＯ−Ａｌ２Ｏ３、ＣｏＯ−Ａｌ２Ｏ３、ＦｅＯ−Ａｌ２Ｏ３、ＣｕＯ−Ａｌ２Ｏ３、ＮｉＯ−Ｃｒ２Ｏ３、ＣｏＯ−Ｃｒ２Ｏ３、ＦｅＯ−Ｃｒ２Ｏ３、ＣｕＯ−Ｃｒ２Ｏ３、Ｆｅ２Ｏ３−ＭｇＯなどの原料の組合せがあげられる。
The combinations forming the all solid solution oxide include NiO—MgO, CoO—MgO, FeO—MgO, and CuO—MgO.
A combination of raw materials such as
As the combination of forming the spinel composite oxide, NiO-Al 2 O 3, CoO-Al 2 O 3, FeO-Al 2 O 3, CuO-Al 2 O 3, NiO-Cr 2 O 3, Examples include a combination of raw materials such as CoO—Cr 2 O 3 , FeO—Cr 2 O 3 , CuO—Cr 2 O 3 , and Fe 2 O 3 —MgO.
次に、前記複合酸化物焼結体を水素など還元性雰囲気中で熱処理還元して、より不安定な金属成分を表面に析出させる。この際の還元性雰囲気ガスとしては、水素ガス、一酸化炭素ガスなどの純ガス、もしくは、これに酸化還元反応に関与しないヘリウムガス、アルゴンガスなどを添加した混合ガスを用いることができる。 Next, the composite oxide sintered body is heat-treated and reduced in a reducing atmosphere such as hydrogen to precipitate a more unstable metal component on the surface. As the reducing atmosphere gas at this time, a pure gas such as hydrogen gas or carbon monoxide gas, or a mixed gas in which helium gas or argon gas that does not participate in the oxidation-reduction reaction is added thereto can be used.
還元による熱処理温度は５００℃〜１１００℃で行うのが好ましい。前記固溶体もしくはスピネル系複合酸化物において５００℃以下の温度で金属粒子を還元し析出させることは難しい。また、１１００℃を超えると析出した金属粒子同士が凝集を起こしやすくなり、結果として均一な組織が得られなくなる。
特に、鉄−アルミニウム系、鉄−マグネシウム系、銅−アルミニウム系の酸化物の場合は、還元による金属粒子析出が５００℃以前より始まるため、好ましい熱処理温度は５００℃〜９００℃である。それ以外の系においては７００℃〜１１００℃が好ましい。
The heat treatment temperature by reduction is preferably 500 ° C. to 1100 ° C. In the solid solution or spinel composite oxide, it is difficult to reduce and deposit metal particles at a temperature of 500 ° C. or lower. On the other hand, when the temperature exceeds 1100 ° C., the precipitated metal particles tend to aggregate and as a result, a uniform structure cannot be obtained.
In particular, in the case of iron-aluminum, iron-magnesium, and copper-aluminum-based oxides, metal particle precipitation due to reduction starts from before 500 ° C., and thus a preferable heat treatment temperature is 500 ° C. to 900 ° C. In other systems, 700 ° C. to 1100 ° C. is preferable.
前記加熱時間は、１〜６０分の範囲が好ましい。熱処理時間がこの範囲を下回ると、還元が充分行われず、金属析出が不十分で、触媒としての機能を発揮することが困難となる。一方、熱処理時間がこの範囲を超えると、析出した金属粒子が凝集を起こし、触媒の分布が不均一になり、触媒機能の低下が生じる。 The heating time is preferably in the range of 1 to 60 minutes. When the heat treatment time is less than this range, the reduction is not sufficiently performed, the metal deposition is insufficient, and it becomes difficult to exhibit the function as a catalyst. On the other hand, when the heat treatment time exceeds this range, the precipitated metal particles cause aggregation, the catalyst distribution becomes non-uniform, and the catalyst function decreases.
本実施の形態によれば、基材となる複合酸化物焼結体を構成する複合酸化物の粒子のサイズを著しく成長させて焼結体自体の高密度化を図るとともに、複合酸化物の粒子と粒子の間の粒界部分を少なく作製できるため、均一で高密度に分散させた金属微粒子組織を得ることができる。
According to the present embodiment, the size of the composite oxide particles constituting the composite oxide sintered body serving as the base material is remarkably grown to increase the density of the sintered body itself, and the composite oxide particles Therefore, a uniform and densely dispersed metal fine particle structure can be obtained.
本実施の形態について実施例によってさらに詳細に説明する。 This embodiment will be described in more detail with reference to examples.
（比較例１）
酸化ニッケル粉末と酸化マグネシウム粉末をそれぞれモル比１：２となるように混合し、プレス成形したのち大気中、１３００℃で２時間焼結して複合酸化物焼結体を得た。次に、前記焼結体を水素雰囲気のもと、１０００℃で１０分間還元処理を行い試料とした。
(Comparative Example 1)
Nickel oxide powder and magnesium oxide powder were mixed so as to have a molar ratio of 1: 2, respectively, press molded, and then sintered in the atmosphere at 1300 ° C. for 2 hours to obtain a composite oxide sintered body. Next, the sintered body was subjected to reduction treatment at 1000 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
（実施例１）
モル比１：２で混合した酸化ニッケル粉末と酸化マグネシウム粉末に、混合粉末の総モル数に対してバナジウム元素量として０．０５モル％となるように五酸化バナジウム粉末を加え、均一になるように混合した。得られた混合粉末をプレス成形し、大気中、１３００℃で２時間焼結した。得られた複合酸化物焼結体を水素雰囲気のもと、１０００℃で１０分間還元処理を行い試料とした。
（比較例２）
バナジウムと同じＶａ族に属する元素としてタンタルがある。モル比１：２で混合した酸化ニッケル粉末と酸化マグネシウム粉末に、タンタルを元素量として０．０５モル％となるように五酸化タンタル粉末を加え、均一になるように混合した。得られた混合粉末をプレス成形し、大気中、１３００℃で２時間焼結した。得られた複合酸化物焼結体を水素雰囲気のもと、１０００℃で１０分間還元処理を行い試料とした。
Example 1
Vanadium pentoxide powder is added to nickel oxide powder and magnesium oxide powder mixed at a molar ratio of 1: 2 so that the amount of vanadium element is 0.05 mol% with respect to the total number of moles of the mixed powder so as to be uniform. Mixed. The obtained mixed powder was press-molded and sintered in air at 1300 ° C. for 2 hours. The obtained composite oxide sintered body was subjected to reduction treatment at 1000 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
(Comparative Example 2)
There is tantalum as an element belonging to the same group Va as vanadium. Tantalum pentoxide powder was added to nickel oxide powder and magnesium oxide powder mixed at a molar ratio of 1: 2 so that the amount of tantalum was 0.05 mol%, and mixed uniformly. The obtained mixed powder was press-molded and sintered in air at 1300 ° C. for 2 hours. The obtained composite oxide sintered body was subjected to reduction treatment at 1000 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
Ｘ線回折による構成相同定の結果、比較例１、比較例２による材料も実施例１による材料も複合酸化物焼結体の組成はニッケル酸化物とマグネシウム酸化物の固溶体であることがわかった。また、これを還元処理したものは、いずれも金属ニッケルのピークと前記酸化物固溶体のピークによる複合体であることがわかった。タンタルおよびバナジウムを含む成分は特に検出されなかった。次に、これら還元処理後の試料についてその微構造を走査型電子顕微鏡（ＳＥＭ）にて観察した。その結果を図１、図２および図３に示す。 As a result of identifying the constituent phases by X-ray diffraction, it was found that the composition of the composite oxide sintered body was a solid solution of nickel oxide and magnesium oxide for both the materials according to Comparative Examples 1 and 2 and Example 1. . Moreover, it turned out that what reduced this is a composite_body | complex with the peak of metallic nickel, and the peak of the said oxide solid solution. No component containing tantalum and vanadium was detected. Next, the microstructure of these reduced samples was observed with a scanning electron microscope (SEM). The results are shown in FIG. 1, FIG. 2 and FIG.
バナジウム成分を添加しない比較例１の材料では、複合酸化物焼結体を構成する複合酸化物の粒子の大きさがおよそ１〜３μｍ程度であることがわかる。また、バナジウムと同じＶａ族に属するタンタルを添加した比較例２の材料でも、複合酸化物を構成する複合酸化物の粒子の大きさが１〜２μｍ程度であることがわかる。これに対し、実施例１の材料では、顕著な粒成長が起こっているのがわかる。その粒子サイズは数１０μｍのレベルで明らかに複合酸化物の粒子の界面（粒界）数は減っている。また、この粒成長により、比較例１および比較例2の材料が比較的多くの気孔を有しているのに対して、実施例１の材料では複合酸化物焼結体全体が緻密質になっているのがわかる。バナジウムを添加しない系の複合酸化物において、焼結温度を１４００℃に、あるいは焼結時間を１０時間以上にしたものも作製したが、観察の結果、それらはいずれも複合酸化物の粒子径が数μｍ程度であった。また、周期表のバナジウムと同じＶａ族に属する他の元素ではこのような巨大粒成長は確認されなかった。これはバナジウムを添加したときに特有の現象であることがわかった。 It can be seen that in the material of Comparative Example 1 in which no vanadium component is added, the size of the composite oxide particles constituting the composite oxide sintered body is about 1 to 3 μm. In addition, it can be seen that even in the material of Comparative Example 2 to which tantalum belonging to the same group Va as vanadium is added, the size of the composite oxide particles constituting the composite oxide is about 1 to 2 μm. On the other hand, it can be seen that remarkable grain growth occurs in the material of Example 1. The number of interfaces (grain boundaries) of the composite oxide particles is clearly reduced at a particle size of several tens of μm. In addition, due to this grain growth, the material of Comparative Example 1 and Comparative Example 2 has a relatively large number of pores, whereas the material of Example 1 makes the entire complex oxide sintered body dense. I can see that In the composite oxide of the system not added with vanadium, a composite oxide having a sintering temperature of 1400 ° C. or a sintering time of 10 hours or more was also produced. It was about several μm. In addition, such giant grain growth was not confirmed in other elements belonging to the same group Va as vanadium in the periodic table. This was found to be a unique phenomenon when vanadium was added.
図４に、バナジウム添加の実施例１をより拡大したＳＥＭ写真を示す。数１０ｎｍサイズのニッケル微粒子が複合酸化物の粒子上に高密度で分散しているのがわかる。粒子径もほぼそろっており、均一な組織となっている。 In FIG. 4, the SEM photograph which expanded Example 1 of addition of vanadium more is shown. It can be seen that nickel fine particles having a size of several tens of nm are dispersed at high density on the composite oxide particles. The particle size is almost the same and the structure is uniform.
実際、バナジウムの添加量については、多く加えてもほとんど同様の効果、組織が見られた。したがって、助剤成分としての添加量は特に限定されないが、バナジウムは希少な元素の一つでもあるため、０．５モル％ぐらいまでが適量と考える。０．５％以下であれば、焼結体の強度等、触媒としての機械的特性が好ましいためである。 In fact, almost the same effect and structure were observed even when a large amount of vanadium was added. Therefore, although the amount added as an auxiliary component is not particularly limited, vanadium is one of the rare elements, so it is considered that an appropriate amount is up to about 0.5 mol%. If it is 0.5% or less, the mechanical properties as a catalyst such as the strength of the sintered body are preferable.
（比較例３）
酸化ニッケル粉末と酸化アルミニウム粉末をモル比で１：２となるように混合し、プレス成形したのち大気中、１４００℃で２時間焼結して複合酸化物焼結体を得た。前記複合酸化物焼結体を水素雰囲気のもと１０００℃で１０分間還元処理を行い試料とした。
(Comparative Example 3)
Nickel oxide powder and aluminum oxide powder were mixed at a molar ratio of 1: 2, press molded, and then sintered in air at 1400 ° C. for 2 hours to obtain a composite oxide sintered body. The composite oxide sintered body was subjected to reduction treatment at 1000 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
（比較例４）
酸化コバルト粉末と酸化マグネシウム粉末をモル比で１：２となるように混合し、プレス成形したのち大気中、１３００℃で２時間焼結して複合酸化物焼結体を得た。次に、前記複合酸化物焼結体を水素雰囲気のもと１０００℃で１０分間還元処理を行い試料とした。
(Comparative Example 4)
Cobalt oxide powder and magnesium oxide powder were mixed at a molar ratio of 1: 2, press molded, and then sintered in the atmosphere at 1300 ° C. for 2 hours to obtain a composite oxide sintered body. Next, the composite oxide sintered body was subjected to reduction treatment at 1000 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
（比較例５）
α型の酸化鉄粉末と酸化マグネシウム粉末をモル比で１：１となるように混合し、プレス成形したのち大気中、１４００℃で２時間焼結して複合酸化物焼結体を得た。次に、前記複合酸化物焼結体を水素雰囲気のもと９００℃で１０分間還元処理を行い試料とした。
(Comparative Example 5)
α-type iron oxide powder and magnesium oxide powder were mixed at a molar ratio of 1: 1, press-molded, and sintered in air at 1400 ° C. for 2 hours to obtain a composite oxide sintered body. Next, the composite oxide sintered body was subjected to reduction treatment at 900 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
（比較例６）
酸化銅粉末と酸化アルミニウム粉末をモル比で１：１となるように混合し、プレス成形したのち大気中、１１５０℃で２時間焼結して複合酸化物焼結体を得た。次に、前記複合酸化物焼結体を水素雰囲気のもと７００℃で１０分間還元処理を行い試料とした。
（比較例７）
酸化ニッケル粉末と酸化クロミウム粉末をモル比で１：１となるように混合し、プレス成形したのち大気中、１４００℃で２時間焼結して複合酸化物焼結体を得た。次に、前記複合酸化物焼結体を水素雰囲気のもと９００℃で１０分間還元処理を行い試料とした。
(Comparative Example 6)
Copper oxide powder and aluminum oxide powder were mixed at a molar ratio of 1: 1, press molded, and then sintered in the atmosphere at 1150 ° C. for 2 hours to obtain a composite oxide sintered body. Next, the composite oxide sintered body was subjected to reduction treatment at 700 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
(Comparative Example 7)
Nickel oxide powder and chromium oxide powder were mixed at a molar ratio of 1: 1, press molded, and then sintered in the atmosphere at 1400 ° C. for 2 hours to obtain a composite oxide sintered body. Next, the composite oxide sintered body was subjected to reduction treatment at 900 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
（実施例２）
モル比１：１で混合した酸化ニッケル粉末と酸化アルミニウム粉末に、バナジウム元素量として０．０５モル％となるように五酸化バナジウム粉末を加え、均一になるように混合した。得られた混合粉末をプレス成形し、大気中、１４００℃で２時間焼結した。得られた複合酸化物焼結体を水素雰囲気のもと、１０００℃で１０分間還元処理を行い試料とした。
(Example 2)
Vanadium pentoxide powder was added to nickel oxide powder and aluminum oxide powder mixed at a molar ratio of 1: 1 so that the vanadium element amount was 0.05 mol%, and mixed uniformly. The obtained mixed powder was press-molded and sintered in air at 1400 ° C. for 2 hours. The obtained composite oxide sintered body was subjected to reduction treatment at 1000 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
（実施例３）
モル比１：２で混合した酸化コバルト粉末と酸化マグネシウム粉末に、バナジウム元素量として０．１モル％となるように五酸化バナジウム粉末を加え、均一になるように混合した。得られた混合粉末をプレス成形し、大気中、１３００℃で２時間焼結した。得られた複合酸化物焼結体を水素雰囲気のもと、１０００℃で１０分間還元処理を行い試料とした。
(Example 3)
Vanadium pentoxide powder was added to cobalt oxide powder and magnesium oxide powder mixed at a molar ratio of 1: 2 so that the amount of vanadium element was 0.1 mol%, and mixed uniformly. The obtained mixed powder was press-molded and sintered in air at 1300 ° C. for 2 hours. The obtained composite oxide sintered body was subjected to reduction treatment at 1000 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
（実施例４）
モル比１：１で混合したα型酸化鉄粉末と酸化マグネシウム粉末に、バナジウム元素量として０．０５モル％となるように五酸化バナジウム粉末を加え、均一になるように混合した。得られた混合粉末をプレス成形し、大気中、１４００℃で２時間焼結した。得られた複合酸化物焼結体を水素雰囲気のもと、９００℃で１０分間還元処理を行い試料とした。
Example 4
Vanadium pentoxide powder was added to α-type iron oxide powder and magnesium oxide powder mixed at a molar ratio of 1: 1 so that the vanadium element amount was 0.05 mol%, and mixed uniformly. The obtained mixed powder was press-molded and sintered in air at 1400 ° C. for 2 hours. The obtained composite oxide sintered body was subjected to a reduction treatment at 900 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
（実施例５）
モル比１：１で混合した酸化銅粉末と酸化アルミニウム粉末に、バナジウム元素量として０．１モル％となるように五酸化バナジウム粉末を加え、均一になるように混合した。得られた混合粉末をプレス成形し、大気中、１１５０℃で２時間焼結した。得られた複合酸化物焼結体を水素雰囲気のもと、７００℃で１０分間還元処理を行い試料とした。
（実施例６）
モル比１：１で混合した酸化ニッケル粉末と酸化クロミウム粉末に、バナジウム元素量として０．１モル％となるように五酸化バナジウム粉末を加え、均一になるように混合した。得られた混合粉末をプレス成形し、大気中、１４００℃で２時間焼結して複合酸化物焼結体を得た。次に、前記複合酸化物焼結体を水素雰囲気のもと９００℃で１０分間還元処理を行い試料とした。
(Example 5)
Vanadium pentoxide powder was added to copper oxide powder and aluminum oxide powder mixed at a molar ratio of 1: 1 so that the amount of vanadium element was 0.1 mol%, and mixed uniformly. The obtained mixed powder was press-molded and sintered in air at 1150 ° C. for 2 hours. The obtained composite oxide sintered body was subjected to reduction treatment at 700 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
(Example 6)
Vanadium pentoxide powder was added to nickel oxide powder and chromium oxide powder mixed at a molar ratio of 1: 1 so that the amount of vanadium element was 0.1 mol%, and mixed uniformly. The obtained mixed powder was press-molded and sintered in air at 1400 ° C. for 2 hours to obtain a composite oxide sintered body. Next, the composite oxide sintered body was subjected to reduction treatment at 900 ° C. for 10 minutes under a hydrogen atmosphere to prepare a sample.
上記表１に示したように、Ｘ線回折試験の結果、前記比較例３では主たる構成相はスピネル型の酸化物ＮｉＡｌ２Ｏ４であった。また、前記比較例４ではコバルト−マグネシウムの固溶体酸化物、前記比較例５ではスピネル型の複合酸化物ＭｇＦｅ２Ｏ４、前記比較例６ではＣｕＡｌ２Ｏ４、前記比較例７ではＮｉＣｒ２Ｏ４の各成分が検出された。これらの複合酸化物焼結体を構成する焼結体の粒子のサイズに関しては、前記比較例５の鉄−マグネシウム系で１０μｍを超えるサイズを示した以外はせいぜい１μｍ程度であった。また、前記比較例５を除いて、気孔も多く含まるものであった。 As shown in Table 1 above, as a result of the X-ray diffraction test, in Comparative Example 3, the main constituent phase was a spinel oxide NiAl 2 O 4 . The comparative example 4 is a solid solution oxide of cobalt-magnesium, the comparative example 5 is a spinel-type composite oxide MgFe 2 O 4 , the comparative example 6 is CuAl 2 O 4 , and the comparative example 7 is NiCr 2 O 4. Each component of was detected. Regarding the size of the particles of the sintered body constituting these composite oxide sintered bodies, it was at most about 1 μm except that the iron-magnesium system of Comparative Example 5 showed a size exceeding 10 μm. Moreover, many pores were included except for the comparative example 5.
これに対し、実施例２〜実施例６における複合酸化物の粒子はそれより１桁〜２桁大きいサイズに成長していた。特に実施例５の鉄−マグネシウム−バナジウム系ではさらに成長して１００μｍを超えるものもあった。密度もより向上しており、バナジウム成分が複合酸化物の粒子の粒子径を大きくするだけではなく、緻密化にも大きく寄与することが明らかになった。いずれの試料においても数ｎｍ〜数１０ｎｍサイズで高密度に分散したニッケルやコバルト、鉄、および銅の粒子が観察された。 On the other hand, the composite oxide particles in Examples 2 to 6 grew to a size one to two orders of magnitude larger than that. In particular, the iron-magnesium-vanadium system of Example 5 further grew and exceeded 100 μm. The density has also been improved, and it has been clarified that the vanadium component not only increases the particle diameter of the composite oxide particles but also greatly contributes to densification. In each sample, particles of nickel, cobalt, iron, and copper dispersed at a high density with a size of several nm to several tens of nm were observed.
以上のように作製された銅系を除く触媒を用いて、エチレンガスを導入し、カーボン合成試験を行った結果、いずれも触媒である金属粒子径より小さな径（数１０ｎｍ）でサイズのそろったカーボンナノ繊維が高密度に生成することが確認された。
銅系触媒の場合は、主にアルコールと水蒸気を反応させて水素を取り出す改質触媒として用いることができる。分散密度が高く、粒子径のそろった本発明による触媒は、より高い改質性能が期待される。
As a result of introducing a carbon gas and conducting a carbon synthesis test using a catalyst excluding the copper-based catalyst prepared as described above, all of them were made smaller in diameter (several tens of nm) than the metal particle diameter as a catalyst. It was confirmed that carbon nanofibers were formed with high density.
In the case of a copper-based catalyst, it can be used mainly as a reforming catalyst that takes out hydrogen by reacting alcohol with water vapor. A catalyst according to the present invention having a high dispersion density and a uniform particle size is expected to have higher reforming performance.
本発明のいくつかの実施形態及び実施例を説明したが、これらの実施形態及び実施例は、例として提示したものであり、発明の範囲を限定することは意図していない。これら新規な実施形態及び実施例は、その他の様々な形態で実施されることが可能であり、発明の要旨を逸脱しない範囲で、種々の省略、置き換え、変更を行うことができる。これら実施形態及び実施例やその変形は、発明の範囲や要旨に含まれるとともに、特許請求の範囲に記載された発明とその均等の範囲に含まれる。 Although several embodiments and examples of the present invention have been described, these embodiments and examples are presented as examples and are not intended to limit the scope of the invention. These novel embodiments and examples can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments, examples, and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
Claims (4)
前記混合物を加熱反応処理して複合酸化物とする工程と、
前記複合酸化物を還元処理しニッケル、コバルト、鉄、銅の少なくとも一種を含む金属微粒子を前記複合酸化物の表面に析出せしめる工程と、
を有する触媒の製造方法。
Mixing at least one selected from nickel, cobalt, iron and copper, at least one selected from aluminum, magnesium and chromium, and a compound containing vanadium;
A step of subjecting the mixture to a heat treatment to form a composite oxide;
Reducing the composite oxide to deposit metal fine particles containing at least one of nickel, cobalt, iron, and copper on the surface of the composite oxide; and
The manufacturing method of the catalyst which has this.
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| JP2014073471A (en) * | 2012-10-05 | 2014-04-24 | Cosmo Oil Co Ltd | Oxidative dehydrogenation catalysts and method of producing the same, and method of producing alkadiene |
| KR101795738B1 (en) | 2016-07-04 | 2017-11-08 | 한국과학기술원 | Method for manufacturing oxide support - metal nanoparticle composites and oxide support - metal nanoparticle composites manufactured by the method |
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