JP2020032331A - Methanation catalyst, manufacturing method therefor, and manufacturing method of methane - Google Patents
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本発明は、メタン化触媒、その製造方法、及びメタンの製造方法に関する。 The present invention relates to a methanation catalyst, a method for producing the same, and a method for producing methane.
従来のメタン化反応はＣＯを原料とした反応であり、石炭由来のＣＯからメタンを製造する方法等として実用化されている。これに対して、ＣＯ２を原料としたメタン化反応は、近年の地球温暖化抑制のためのＣＯ２排出量削減の観点から注目されているが、未だ実用化には至っておらず、貴金属であるＲｕやベースメタル元素であるＮｉが、ＣＯ２を原料としたメタン化反応において高い活性を示す触媒として検討されている。 The conventional methanation reaction is a reaction using CO as a raw material, and has been put to practical use as a method for producing methane from CO derived from coal. On the other hand, the methanation reaction using CO 2 as a raw material has attracted attention from the viewpoint of reducing CO 2 emissions for suppressing global warming in recent years. Certain Ru and Ni as a base metal element have been studied as catalysts having high activity in the methanation reaction using CO 2 as a raw material.
しかしながら、貴金属触媒は高コストであるため、製造コストの面では、メタン化触媒としてベースメタル元素を使用することが望ましいが、ベースメタル元素は反応温度によって活性が低くなる場合があり、ＣＯ２転化率が必ずしも十分に高いものではなかった。 However, since noble metal catalysts are expensive, it is desirable to use a base metal element as a methanation catalyst in terms of production cost. However, the activity of the base metal element may be lowered depending on the reaction temperature, and CO 2 conversion may occur. The rates were not always high enough.
例えば、特開平８−１２７５４４号公報（特許文献１）には、硝酸セリウムと硝酸ニッケルを溶解させた水溶液（Ｃｅ：Ｎｉ＝１：５）に炭酸ナトリウム水溶液を加えて中和し、共沈により生成したセリウムとニッケルの炭酸塩をろ別して焼成して得た混合酸化物が記載されている。この混合酸化物を触媒として二酸化炭素と水素とからメタンを製造した場合、３００℃以上の反応温度では高いメタン収率が得られるものの、２５０℃以下の反応温度では十分に高いメタン収率は得られていない。 For example, JP-A-8-127544 (Patent Document 1) discloses that an aqueous solution of cerium nitrate and nickel nitrate (Ce: Ni = 1: 5) is neutralized by adding an aqueous solution of sodium carbonate, and coprecipitation is performed. A mixed oxide obtained by filtering and firing the produced carbonate of cerium and nickel is described. When methane is produced from carbon dioxide and hydrogen using this mixed oxide as a catalyst, a high methane yield is obtained at a reaction temperature of 300 ° C. or higher, but a sufficiently high methane yield is obtained at a reaction temperature of 250 ° C. or lower. Not been.
また、特開２０１１−２０６７７０号公報（特許文献２）には、ジルコニアのヒドロゾルにＣｅ等の安定化元素の塩の水溶液と鉄族元素の塩の水溶液とを混合し、得られた混合物を濃縮・乾固・焼成して触媒前駆体を形成し、この触媒前駆体を還元処理することによってメタン化反応用触媒が得られることが記載されている。このメタン化反応用触媒の２５０℃以下の反応温度でのＣＯ２転化率（メタン収率）は特許文献１の混合酸化物に比べて高くなっているものの、必ずしも十分に高いものではなかった。 JP-A-2011-206770 (Patent Document 2) discloses that a zirconia hydrosol is mixed with an aqueous solution of a salt of a stabilizing element such as Ce and an aqueous solution of a salt of an iron group element, and the resulting mixture is concentrated. It describes that a catalyst for a methanation reaction can be obtained by forming a catalyst precursor by drying and calcining, and subjecting the catalyst precursor to a reduction treatment. The CO 2 conversion (methane yield) of this methanation reaction catalyst at a reaction temperature of 250 ° C. or lower was higher than that of the mixed oxide of Patent Document 1, but was not necessarily sufficiently high.
本発明は、上記従来技術の有する課題に鑑みてなされたものであり、低温（例えば、２５０℃以下）であっても高い触媒活性を示すメタン化触媒、その製造方法、及びこのメタン化触媒を用いたメタンの製造方法を提供することを目的とする。 The present invention has been made in view of the above-mentioned problems of the related art, and provides a methanation catalyst exhibiting high catalytic activity even at a low temperature (for example, 250 ° C. or lower), a method for producing the methanation catalyst, and a methanation catalyst. An object of the present invention is to provide a method for producing methane used.
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、共沈法によって製造された、セリア微粒子と鉄族金属元素を含む微粒子とを含有するメタン化触媒において、沈殿剤由来のＮａが二酸化炭素のメタン化反応を阻害することを見出した。そして、本発明者らは、このＮａの含有量を１ａｔ％以下に低減することによって、低温（例えば、２５０℃以下）であっても二酸化炭素のメタン化反応において高い触媒活性（メタン化触媒活性）が得られることを見出し、本発明を完成するに至った。 The present inventors have conducted intensive studies to achieve the above object, and as a result, in a methanation catalyst containing ceria fine particles and fine particles containing an iron group metal element, produced by a coprecipitation method, Na was found to inhibit the methanation reaction of carbon dioxide. By reducing the Na content to 1 at% or less, the present inventors have achieved a high catalytic activity (methanization catalytic activity) in the methanation reaction of carbon dioxide even at a low temperature (for example, 250 ° C. or less). ) Was obtained, and the present invention was completed.
すなわち、本発明のメタン化触媒は、セリア微粒子と鉄族金属又はその酸化物からなる鉄族金属元素含有微粒子とを含有するメタン化触媒であって、
前記メタン化触媒全体について蛍光Ｘ線分析法により測定した鉄族金属元素の含有量がＣｅと鉄族金属元素との合計量に対して１５〜８０質量％であり、
前記メタン化触媒全体について蛍光Ｘ線分析法により測定した鉄族金属元素の含有量に対する、前記メタン化触媒において無作為に抽出した２０点の測定領域（１μｍφ×１μｍ深さ）についてエネルギー分散型Ｘ線分光分析法により測定した鉄族金属元素の含有量の標準偏差が４以下であり、
Ｎａ含有量が１ａｔ％以下である、
ことを特徴とするものである。このようなメタン化触媒においては、前記鉄族金属元素含有微粒子の平均粒子径が０．５〜１０ｎｍであることが好ましい。
That is, the methanation catalyst of the present invention is a methanation catalyst containing ceria fine particles and iron group metal element-containing fine particles composed of an iron group metal or an oxide thereof,
The content of the iron group metal element measured by X-ray fluorescence analysis for the entire methanation catalyst is 15 to 80% by mass based on the total amount of Ce and the iron group metal element,
With respect to the content of the iron group metal element measured by the fluorescent X-ray analysis method for the entire methanation catalyst, energy dispersive X-ray analysis was performed for 20 measurement areas (1 μmφ × 1 μm depth) randomly extracted in the methanation catalyst. The standard deviation of the iron group metal element content measured by X-ray spectroscopy is 4 or less,
Na content is 1 at% or less,
It is characterized by the following. In such a methanation catalyst, the average particle diameter of the iron group metal element-containing fine particles is preferably 0.5 to 10 nm.
本発明の第一のメタン化触媒の製造方法は、セリウムイオンと鉄族金属イオンとを含有する前駆体溶液にＮａを含有する沈殿剤を添加してセリウム化合物と鉄族金属化合物とを含有する共沈物を生成させ、該共沈物をＮａ含有量が１ａｔ％以下になるまで洗浄した後、前記セリウム化合物と前記鉄族金属化合物とをセリア微粒子と鉄族金属又はその酸化物からなる鉄族金属元素含有微粒子とにそれぞれ変換せしめることを特徴とする方法である。このよう第一のメタン化触媒の製造方法においては、前記Ｎａを含有する沈殿剤が水酸化ナトリウム及び炭酸ナトリウムのうちの少なくとも一方であることが好ましい。 The first method for producing a methanation catalyst of the present invention contains a cerium compound and an iron group metal compound by adding a precipitant containing Na to a precursor solution containing cerium ions and an iron group metal ion. After forming a coprecipitate and washing the coprecipitate until the Na content becomes 1 at% or less, the cerium compound and the iron group metal compound are mixed with ceria fine particles and an iron group metal or an oxide thereof. The method is characterized in that the fine particles are converted into group metal element-containing fine particles. In such a first method for producing a methanation catalyst, the Na-containing precipitant is preferably at least one of sodium hydroxide and sodium carbonate.
本発明の第二のメタン化触媒の製造方法は、セリウムイオンと鉄族金属イオンとを含有する前駆体溶液にＮａを含有しない沈殿剤を添加してセリウム化合物と鉄族金属化合物とを含有する共沈物を生成させた後、前記セリウム化合物と前記鉄族金属化合物とをセリア微粒子と鉄族金属又はその酸化物からなる鉄族金属元素含有微粒子とにそれぞれ変換せしめることを特徴とする方法である。このよう第二のメタン化触媒の製造方法においては、前記Ｎａを含有しない沈殿剤が炭酸水素アンモニウムであることが好ましい。 The second method for producing a methanation catalyst of the present invention contains a cerium compound and an iron group metal compound by adding a precipitant not containing Na to a precursor solution containing cerium ions and iron group metal ions. After forming a coprecipitate, a method characterized in that the cerium compound and the iron group metal compound are respectively converted into ceria fine particles and iron group metal element-containing fine particles composed of an iron group metal or an oxide thereof. is there. In such a second method for producing a methanation catalyst, the Na-free precipitant is preferably ammonium bicarbonate.
本発明のメタンの製造方法は、前記本発明のメタン化触媒に二酸化炭素と水素との混合ガスを接触せしめることを特徴とする方法である。 The method for producing methane of the present invention is a method characterized by contacting a mixed gas of carbon dioxide and hydrogen with the methanation catalyst of the present invention.
なお、本発明のメタン化触媒が低温（例えば、２５０℃以下）であっても高いメタン化触媒活性を示す理由は必ずしも定かではないが、本発明者らは以下のように推察する。すなわち、本発明のメタン化触媒は、セリア微粒子と鉄族金属元素を含む微粒子（鉄族金属元素含有微粒子）とを共沈法によって形成させた二次粒子からなるものである。このような共沈法によって製造した二次粒子においては、二酸化炭素との親和性が高いセリア微粒子の表面又は内部に二酸化炭素のメタン化反応において触媒活性点となる鉄族金属元素含有微粒子が均一に分散している。これにより、セリア微粒子と鉄族金属元素含有微粒子との接触界面が増加するため、セリア微粒子による二酸化炭素の吸着性能と鉄族金属元素含有微粒子による触媒性能との相乗効果によって、本発明のメタン化触媒は低温（例えば、２５０℃以下）であっても高いメタン化触媒活性を示すと推察される。 The reason why the methanation catalyst of the present invention exhibits high methanation catalyst activity even at a low temperature (for example, 250 ° C. or lower) is not always clear, but the present inventors presume as follows. That is, the methanation catalyst of the present invention is composed of secondary particles formed by coprecipitation of ceria fine particles and fine particles containing an iron group metal element (fine particles containing an iron group metal element). In the secondary particles produced by such a coprecipitation method, fine particles containing an iron group metal element which is a catalytic active site in the methanation reaction of carbon dioxide are uniformly formed on the surface or inside of the ceria fine particles having a high affinity for carbon dioxide. Is dispersed. As a result, the contact interface between the ceria fine particles and the iron group metal element-containing fine particles increases, so that the synergistic effect of the carbon dioxide adsorption performance of the ceria fine particles and the catalytic performance of the iron group metal element containing fine particles leads to the methanation of the present invention. It is assumed that the catalyst exhibits high methanation catalytic activity even at low temperatures (for example, 250 ° C. or lower).
一方、含浸法によりセリア微粒子に鉄族金属元素含有微粒子を担持させた場合には、共沈法により製造した本発明のメタン化触媒に比べて、鉄族金属元素含有微粒子が不均一に分散している。このため、セリア微粒子と鉄族金属元素含有微粒子との接触界面が少なく、セリア微粒子による二酸化炭素の吸着性能と鉄族金属元素含有微粒子による触媒性能との相乗効果が十分に得られないため、低温（例えば、２５０℃以下）でのメタン化触媒活性が低くなると推察される。 On the other hand, when the iron-group metal element-containing fine particles are supported on the ceria fine particles by the impregnation method, the iron-group metal element-containing fine particles are non-uniformly dispersed as compared with the methanation catalyst of the present invention manufactured by the coprecipitation method. ing. Therefore, the contact interface between the ceria fine particles and the iron group metal element-containing fine particles is small, and the synergistic effect of the carbon dioxide adsorption performance of the ceria fine particles and the catalytic performance of the iron group metal element-containing fine particles cannot be sufficiently obtained. It is assumed that the methanation catalyst activity at (for example, 250 ° C. or lower) becomes low.
また、ジルコニア微粒子、チタニア微粒子、アルミナ微粒子に鉄族金属元素含有微粒子を担持させた場合には、これらの微粒子がセリア微粒子に比べて二酸化炭素の吸着性能に劣るため、低温（例えば、２５０℃以下）でのメタン化触媒活性が更に低くなると推察される。 Further, when iron-group metal element-containing fine particles are supported on zirconia fine particles, titania fine particles, and alumina fine particles, these fine particles are inferior in carbon dioxide adsorption performance as compared with ceria fine particles. It is presumed that the methanation catalyst activity in ()) further decreases.
本発明によれば、低温（例えば、２５０℃以下）であっても高い触媒活性を示すメタン化触媒を得ることができる。また、このような本発明のメタン化触媒を用いることによって、低温（例えば、２５０℃以下）であっても二酸化炭素と水素とから高収率でメタンを製造することが可能となる。 According to the present invention, a methanation catalyst exhibiting high catalytic activity even at a low temperature (for example, 250 ° C. or lower) can be obtained. Further, by using such a methanation catalyst of the present invention, methane can be produced in high yield from carbon dioxide and hydrogen even at a low temperature (for example, 250 ° C. or lower).
以下、本発明をその好適な実施形態に即して詳細に説明する。 Hereinafter, the present invention will be described in detail with reference to preferred embodiments.
〔メタン化触媒〕
先ず、本発明のメタン化触媒について説明する。本発明のメタン化触媒は、セリア微粒子と鉄族金属又はその酸化物からなる鉄族金属元素含有微粒子とを含有するものである。
(Methanation catalyst)
First, the methanation catalyst of the present invention will be described. The methanation catalyst of the present invention contains fine ceria particles and fine particles containing an iron group metal element composed of an iron group metal or an oxide thereof.
本発明のメタン化触媒において、前記鉄族金属元素含有微粒子は鉄族金属又はその酸化物からなるものである。前記鉄族金属及びその酸化物としては、ニッケル、鉄、コバルト、酸化ニッケル、酸化鉄、酸化コバルトが挙げられる。このような鉄族金属及びその酸化物は１種を単独で使用しても２種以上を併用してもよい。これらの鉄族金属及びその酸化物の中でも、触媒活性に優れているという観点から、ニッケル、酸化ニッケルが好ましい。 In the methanation catalyst of the present invention, the fine particles containing an iron group metal element are made of an iron group metal or an oxide thereof. Examples of the iron group metal and its oxide include nickel, iron, cobalt, nickel oxide, iron oxide, and cobalt oxide. Such iron group metals and oxides thereof may be used alone or in combination of two or more. Among these iron group metals and oxides thereof, nickel and nickel oxide are preferred from the viewpoint of excellent catalytic activity.
このような鉄族金属元素含有微粒子の平均粒子径としては特に制限はないが、０．５〜１０ｎｍが好ましく、１〜１０ｎｍがより好ましい。鉄族金属元素含有微粒子の平均粒子径が前記下限未満になると、加熱時の粒成長により触媒性能が低下しやすい傾向にあり、他方、前記上限を超えると、触媒活性点が少ないため、触媒性能が低下する傾向にある。なお、前記鉄族金属元素含有微粒子の平均粒子径は、例えば、粉末Ｘ線回折測定等により求めることができる。 The average particle size of such fine particles containing an iron group metal element is not particularly limited, but is preferably 0.5 to 10 nm, more preferably 1 to 10 nm. When the average particle diameter of the iron group metal element-containing fine particles is less than the lower limit, the catalytic performance tends to be reduced due to grain growth during heating. Tends to decrease. The average particle diameter of the iron group metal element-containing fine particles can be determined, for example, by powder X-ray diffraction measurement or the like.
また、本発明のメタン化触媒において、セリア微粒子の平均粒子径としては特に制限はないが、１〜２０ｎｍが好ましく、１．５〜１０ｎｍがより好ましく、２〜６ｎｍが特に好ましい。セリア微粒子の平均粒子径が前記下限未満になると、加熱時の粒成長により比表面積が減少しやすい傾向にあり、他方、前記上限を超えると、触媒を均一に高分散しにくい傾向にある。なお、前記セリア微粒子の平均粒子径は、例えば、粉末Ｘ線回折測定等により求めることができる。 In the methanation catalyst of the present invention, the average particle diameter of the ceria fine particles is not particularly limited, but is preferably 1 to 20 nm, more preferably 1.5 to 10 nm, and particularly preferably 2 to 6 nm. When the average particle diameter of the ceria fine particles is less than the lower limit, the specific surface area tends to decrease due to the grain growth during heating. On the other hand, when the average particle diameter exceeds the upper limit, the catalyst tends to be difficult to be uniformly and highly dispersed. The average particle diameter of the ceria fine particles can be determined, for example, by powder X-ray diffraction measurement or the like.
本発明のメタン化触媒は、このようなセリア微粒子と鉄族金属元素含有微粒子とを含有するものである。本発明のメタン化触媒において、メタン化触媒全体についての鉄族金属元素の含有量は、メタン化触媒全体についてのＣｅと鉄族金属元素との合計量に対して１５〜８０質量％である。メタン化触媒全体についての鉄族金属元素の含有量が前記下限未満になると、二酸化炭素のメタン化反応における触媒活性点が少なくなるため、低温（例えば、２５０℃以下）でのメタン化触媒活性が低下し、他方、前記上限を超えると、相対的に二酸化炭素の吸着サイトであるセリア微粒子の量が少なくなるため、二酸化炭素の吸着量が減少し、低温（例えば、２５０℃以下）でのメタン化触媒活性が低下する。このようなメタン化触媒全体についての鉄族金属元素の含有量としては、低温（例えば、２５０℃以下）でのメタン化触媒活性が向上するという観点から、メタン化触媒全体についてのＣｅと鉄族金属元素との合計量に対して、２５〜７０質量％が好ましく、３０〜６０質量％がより好ましい。なお、メタン化触媒全体についてのＣｅ及び鉄族金属元素の含有量は蛍光Ｘ線分析法（ＸＲＦ分析法）により測定した値である。 The methanation catalyst of the present invention contains such fine ceria particles and fine particles containing an iron group metal element. In the methanation catalyst of the present invention, the content of the iron group metal element in the entire methanation catalyst is 15 to 80% by mass based on the total amount of Ce and the iron group metal element in the entire methanation catalyst. When the content of the iron group metal element in the entire methanation catalyst is less than the lower limit, the catalytic activity in the methanation reaction of carbon dioxide decreases, so that the methanation catalytic activity at a low temperature (for example, 250 ° C. or lower) is reduced. On the other hand, if it exceeds the upper limit, the amount of ceria fine particles that are carbon dioxide adsorption sites is relatively small, so that the amount of carbon dioxide adsorbed is reduced, and methane at a low temperature (for example, 250 ° C. or lower) is used. Catalyst activity decreases. From the viewpoint that the methanation catalyst activity at a low temperature (for example, 250 ° C. or less) is improved, the content of the iron group metal element in the entire methanation catalyst is set to Ce and iron group in the entire methanation catalyst. The amount is preferably from 25 to 70% by mass, more preferably from 30 to 60% by mass, based on the total amount with the metal element. The contents of Ce and the iron group metal element in the entire methanation catalyst are values measured by X-ray fluorescence analysis (XRF analysis).
また、本発明のメタン化触媒においては、メタン化触媒全体についての鉄族金属元素の含有量に対する、無作為に抽出した２０点の測定領域（１μｍφ×１μｍ深さ）について測定した鉄族金属元素の含有量の標準偏差が４以下である。前記鉄族金属元素の含有量の標準偏差が前記上限以下のメタン化触媒は、鉄族金属元素含有微粒子が均一に分散したもの（鉄族金属元素含有微粒子の分散性が高いもの）であり、低温（例えば、２５０℃以下）でのメタン化触媒活性に優れている。このような鉄族金属元素の含有量の標準偏差としては、低温（例えば、２５０℃以下）でのメタン化触媒活性が向上するという観点から、３以下が好ましく、２以下がより好ましい。なお、メタン化触媒全体についての鉄族金属元素の含有量は蛍光Ｘ線分析法（ＸＲＦ分析法）により測定した値であり、メタン化触媒において無作為に抽出した２０点の測定領域（１μｍφ×１μｍ深さ）について測定した鉄族金属元素の含有量はエネルギー分散型Ｘ線分光分析法（ＥＤＸ法）により測定した値である。 Further, in the methanation catalyst of the present invention, the iron group metal element measured in 20 measurement areas (1 μmφ × 1 μm depth) randomly extracted with respect to the content of the iron group metal element in the entire methanation catalyst. Is 4 or less. The methanation catalyst in which the standard deviation of the content of the iron group metal element is equal to or less than the upper limit is one in which the iron group metal element-containing fine particles are uniformly dispersed (the iron group metal element-containing fine particles have high dispersibility), Excellent methanation catalyst activity at low temperatures (for example, 250 ° C. or lower). The standard deviation of the content of the iron group metal element is preferably 3 or less, more preferably 2 or less, from the viewpoint that the methanation catalyst activity at low temperatures (for example, 250 ° C. or less) is improved. The content of the iron group metal element in the entire methanation catalyst is a value measured by X-ray fluorescence analysis (XRF analysis), and 20 measurement areas (1 μmφ × 1) randomly extracted in the methanation catalyst. (1 μm depth) is a value measured by energy dispersive X-ray spectroscopy (EDX method).
さらに、本発明のメタン化触媒においては、Ｎａ含有量が１ａｔ％以下である。Ｎａ含有量が前記上限を超えると、二酸化炭素のメタン化反応が阻害されるため、メタンの収率が低下する。 Further, in the methanation catalyst of the present invention, the Na content is 1 at% or less. If the Na content exceeds the upper limit, the methanation reaction of carbon dioxide is inhibited, and the methane yield decreases.
本発明のメタン化触媒は、セリア微粒子及び鉄族金属元素含有微粒子のみからなるものであってもよいが、ジルコニア及び希土類金属酸化物からなる群から選択される少なくとも１種の金属酸化物の微粒子（以下、「他の金属酸化物微粒子」という）が更に含まれていてもよい。このようなジルコニア微粒子等の他の金属酸化物微粒子を含有することによって、セリア微粒子の熱安定性が向上し、メタン化触媒の耐熱性が向上する。 The methanation catalyst of the present invention may be composed of only ceria fine particles and iron-group metal element-containing fine particles, but fine particles of at least one metal oxide selected from the group consisting of zirconia and rare earth metal oxides. (Hereinafter, referred to as “other metal oxide fine particles”). By containing such other metal oxide fine particles such as zirconia fine particles, the thermal stability of the ceria fine particles is improved, and the heat resistance of the methanation catalyst is improved.
前記他の金属酸化物微粒子の含有量としては、前記他の金属酸化物微粒子を構成する金属元素の含有量が、メタン化触媒に含まれる全金属元素１００モル％に対して、２〜２０モル％となる量が好ましく、３〜１５モル％がとなる量がより好ましい。前記他の金属酸化物微粒子の含有量が前記下限未満になると、メタン化触媒の耐熱性が十分に向上しない場合があり、他方、前記上限を超えると、セリア微粒子と鉄族金属元素含有微粒子との相互作用が得られにくい傾向にある。 As the content of the other metal oxide fine particles, the content of the metal element constituting the other metal oxide fine particles is 2 to 20 mol based on 100 mol% of all metal elements contained in the methanation catalyst. %, And more preferably 3 to 15 mol%. When the content of the other metal oxide fine particles is less than the lower limit, the heat resistance of the methanation catalyst may not be sufficiently improved.On the other hand, when the content exceeds the upper limit, ceria fine particles and iron group metal element-containing fine particles may be used. Tend to be difficult to obtain.
〔メタン化触媒の製造方法〕
次に、本発明のメタン化触媒の製造方法について説明する。本発明のメタン化触媒の製造方法は、セリウムイオンと鉄族金属イオンとを含有する前駆体溶液にＮａを含有する沈殿剤を添加してセリウム化合物と鉄族金属化合物とを含有する共沈物を生成させ、この共沈物をＮａ含有量が１ａｔ％以下になるまで洗浄した後、前記セリウム化合物をセリア微粒子に、前記鉄族金属化合物を鉄族金属又はその酸化物からなる鉄族金属元素含有微粒子に、それぞれ変換せしめる方法（第一のメタン化触媒の製造方法）である。
(Production method of methanation catalyst)
Next, a method for producing the methanation catalyst of the present invention will be described. The method for producing a methanation catalyst according to the present invention comprises a coprecipitate containing a cerium compound and an iron group metal compound by adding a precipitant containing Na to a precursor solution containing cerium ions and an iron group metal ion. After washing the coprecipitate until the Na content becomes 1 at% or less, the cerium compound is converted to ceria fine particles, and the iron group metal compound is changed to an iron group metal or an iron group metal element comprising an oxide thereof. This is a method (a method for producing a first methanation catalyst) of converting each of the particles into contained fine particles.
セリウムイオンと鉄族金属イオンとを含有する前駆体溶液としては特に制限はないが、例えば、溶媒にセリウムの塩と鉄族金属の塩とを溶解した前駆体溶液が挙げられる。また、得られるメタン化触媒の耐熱性を向上させるために、この前駆体溶液に、ジルコニウム及び希土類金属からなる群から選択される少なくとも１種の金属（以下、「他の金属」という）の塩を添加してもよい。セリウムの塩、鉄族金属の塩及び他の金属の塩としては、これらの金属の硝酸塩、酢酸塩、塩化物等が挙げられる。溶媒としては、セリウムの塩、鉄族金属の塩及び他の金属の塩が溶解し、沈殿剤を添加することによって共沈物が生成する溶媒であれば特に制限はなく、例えば、水、エタノール、メタノール等、及び、水とエタノール、メタノール等との混合溶媒が挙げられる。 The precursor solution containing cerium ions and iron group metal ions is not particularly limited, and includes, for example, a precursor solution in which a cerium salt and an iron group metal salt are dissolved in a solvent. Further, in order to improve the heat resistance of the obtained methanation catalyst, a salt of at least one metal (hereinafter, referred to as “other metal”) selected from the group consisting of zirconium and a rare earth metal is added to the precursor solution. May be added. The salts of cerium, salts of iron group metals and salts of other metals include nitrates, acetates, chlorides and the like of these metals. The solvent is not particularly limited as long as it is a solvent in which a salt of cerium, a salt of an iron group metal and a salt of another metal are dissolved, and a coprecipitate is formed by adding a precipitant, for example, water, ethanol , Methanol and the like, and a mixed solvent of water and ethanol, methanol and the like.
前述の前駆体溶液において、セリウムイオン、鉄族金属イオンの含有量としては、得られるメタン化触媒中のセリア微粒子と鉄族金属元素含有微粒子の質量比（セリア微粒子／鉄族金属元素含有微粒子）が１５／８０〜８０／２０となる量が好ましく、２５／７５〜７０／３０となる量がより好ましく、３０／７０〜６０／４０となる量が更に好ましい。セリア微粒子／鉄族金属元素含有微粒子が前記下限未満になると、二酸化炭素のメタン化反応における触媒活性点が少なくなるため、低温（例えば、２５０℃以下）でのメタン化触媒活性が低下する傾向にあり、他方、前記上限を超えると、相対的に二酸化炭素の吸着サイトであるセリア微粒子の量が少なくなるため、二酸化炭素の吸着量が減少し、低温（例えば、２５０℃以下）でのメタン化触媒活性が低下する傾向にある。 In the above-mentioned precursor solution, the content of cerium ions and iron group metal ions is determined by the mass ratio of ceria fine particles to iron group metal element-containing fine particles in the obtained methanation catalyst (ceria fine particles / iron group metal element-containing fine particles). Is preferably from 15/80 to 80/20, more preferably from 25/75 to 70/30, even more preferably from 30/70 to 60/40. When the ratio of ceria fine particles / iron group metal element-containing fine particles is less than the above lower limit, the catalytic activity in the methanation reaction of carbon dioxide decreases, so that the methanation catalytic activity at a low temperature (for example, 250 ° C. or lower) tends to decrease. On the other hand, if the upper limit is exceeded, the amount of ceria fine particles, which are sites for adsorbing carbon dioxide, becomes relatively small, so that the amount of carbon dioxide adsorbed decreases, and methanation at a low temperature (for example, 250 ° C. or lower) occurs. The catalytic activity tends to decrease.
また、前述の前駆体溶液において、他の金属イオンの含有量としては、得られるメタン化触媒中の他の金属酸化物微粒子を構成する金属元素の含有量が、メタン化触媒に含まれる全金属元素１００モル％に対して、２〜２０モル％となる量が好ましく、３〜１５モル％がとなる量がより好ましい。前記他の金属イオンの含有量が前記下限未満になると、メタン化触媒の耐熱性が十分に向上しない場合があり、他方、前記上限を超えると、セリア微粒子と鉄族金属元素含有微粒子との相互作用が得られにくい傾向にある。 In the precursor solution described above, the content of the other metal ions in the obtained methanation catalyst is determined by the content of the metal element constituting the other metal oxide fine particles in the obtained methanation catalyst. The amount is preferably 2 to 20 mol%, more preferably 3 to 15 mol%, based on 100 mol% of the element. When the content of the other metal ion is less than the lower limit, the heat resistance of the methanation catalyst may not be sufficiently improved, while when the content exceeds the upper limit, the interaction between the ceria fine particles and the iron group metal element-containing fine particles may not be improved. The effect tends to be difficult to obtain.
前記第一のメタン化触媒の製造方法においては、先ず、セリウムイオンと鉄族金属イオンとを含有し、必要に応じて他の金属イオンを更に含有する前駆体溶液に、Ｎａを含有する沈殿剤を添加する。これにより、セリウム化合物と鉄族金属化合物とを含有し、必要に応じて他の金属化合物を更に含有する共沈物が生成する。前記第一のメタン化触媒の製造方法に用いられるＮａを含有する沈殿剤としては、水酸化ナトリウム、炭酸ナトリウムが挙げられる。これらの沈殿剤は１種を単独で使用しても２種以上を併用してもよい。 In the first method for producing a methanation catalyst, first, a precipitant containing Na and containing a cerium ion and an iron group metal ion, and further containing another metal ion as necessary. Is added. Thereby, a coprecipitate containing the cerium compound and the iron group metal compound and further containing other metal compounds as necessary is generated. Examples of the precipitant containing Na used in the method for producing the first methanation catalyst include sodium hydroxide and sodium carbonate. One of these precipitants may be used alone, or two or more thereof may be used in combination.
このようにして得られる共沈物においては、鉄族金属化合物が均一に分散しており、得られるメタン化触媒は、鉄族金属元素含有微粒子の分散性が高いものであり、低温（例えば、２５０℃以下）であっても高いメタン化触媒活性を示す。一方、含浸法によりセリア微粒子に鉄族金属元素含有微粒子を担持させた場合には、鉄族金属元素含有微粒子の分散性が低く、低温（例えば、２５０℃以下）でのメタン化触媒活性が低下する。 In the coprecipitate thus obtained, the iron group metal compound is uniformly dispersed, and the obtained methanation catalyst has a high dispersibility of the iron group metal element-containing fine particles, and has a low temperature (for example, (250 ° C. or less) even at high temperatures. On the other hand, when the iron-group metal element-containing fine particles are supported on the ceria fine particles by the impregnation method, the dispersibility of the iron-group metal element-containing fine particles is low, and the methanation catalytic activity at a low temperature (for example, 250 ° C. or lower) decreases. I do.
このようにして得られる共沈物には、沈殿剤に由来するＮａが含まれており、このＮａが二酸化炭素のメタン化反応を阻害する。このため、前記第一のメタン化触媒の製造方法においては、得られた共沈物を洗浄してＮａを除去する。洗浄操作は、Ｎａ含有量が１ａｔ％以下に低減されるまで繰返し実施する。洗浄に用いる溶媒としては、共沈物が溶解せず、Ｎａを除去できる溶媒であれば特に制限はなく、例えば、水（例えば、室温〜７０℃の温水）等が挙げられる。 The coprecipitate thus obtained contains Na derived from the precipitant, and this Na inhibits the methanation reaction of carbon dioxide. Therefore, in the first method for producing a methanation catalyst, the obtained coprecipitate is washed to remove Na. The washing operation is repeatedly performed until the Na content is reduced to 1 at% or less. The solvent used for washing is not particularly limited as long as the coprecipitate does not dissolve and Na can be removed, and examples thereof include water (for example, warm water at room temperature to 70 ° C.).
次に、このようにしてＮａ含有量が低減された共沈物を、例えば、大気中で焼成して、前記セリウム化合物をセリア微粒子に、前記鉄族金属化合物を鉄族金属元素含有微粒子に、必要に応じて含まれる前記他の金属化合物を他の金属酸化物微粒子に、それぞれ変換させる。これにより、本発明のメタン化触媒を得ることができる。 Next, the coprecipitate having a reduced Na content in this manner is, for example, fired in the air to convert the cerium compound into ceria fine particles, and the iron group metal compound into iron group metal element-containing fine particles. The other metal compounds contained as necessary are converted into other metal oxide fine particles. Thereby, the methanation catalyst of the present invention can be obtained.
共沈物の焼成温度としては特に制限はないが、３５０〜６００℃が好ましく、４００〜５００℃がより好ましい。共沈物の焼成時間としては特に制限はないが、０．５〜５時間が好ましく、１〜３時間がより好ましい。 The firing temperature of the coprecipitate is not particularly limited, but is preferably 350 to 600 ° C, more preferably 400 to 500 ° C. The time for firing the coprecipitate is not particularly limited, but is preferably 0.5 to 5 hours, more preferably 1 to 3 hours.
また、本発明のメタン化触媒の製造方法においては、Ｎａを含有する沈殿剤の代わりにＮａを含有しない沈殿剤を用いることによって、前記第一のメタン化触媒の製造方法において、共沈物をＮａ含有量が１ａｔ％以下になるまで洗浄する操作を省略することができる。すなわち、セリウムイオンと鉄族金属イオンとを含有し、必要に応じて他の金属イオンを更に含有する前駆体溶液に、Ｎａを含有しない沈殿剤を添加して、セリウム化合物と鉄族金属化合物とを含有し、必要に応じて他の金属化合物を更に含有する共沈物を生成させた後、前記セリウム化合物をセリア微粒子に、前記鉄族金属化合物を鉄族金属元素含有微粒子に、必要に応じて含有する前記他の金属化合物を他の金属酸化物微粒子に、それぞれ変換せしめる方法〔第二のメタン化触媒の製造方法〕によって、セリア微粒子と鉄族金属元素含有微粒子と含有し、必要に応じて他の金属酸化物微粒子を更に含有する本発明のメタン化触媒を製造することもできる。 Further, in the method for producing a methanation catalyst of the present invention, a coprecipitate is produced in the first method for producing a methanation catalyst by using a precipitant not containing Na instead of a precipitant containing Na. The washing operation until the Na content becomes 1 at% or less can be omitted. That is, a precursor solution containing cerium ions and iron group metal ions, and further containing other metal ions as necessary, is added with a Na-free precipitant, and the cerium compound and iron group metal compound Containing, if necessary, a coprecipitate further containing another metal compound, and then the cerium compound is converted into ceria fine particles, and the iron group metal compound is converted into iron group metal element-containing fine particles. By the method of converting the other metal compound to be contained into other metal oxide fine particles (the method for producing the second methanation catalyst), containing ceria fine particles and iron group metal element-containing fine particles, if necessary. Thus, the methanation catalyst of the present invention further containing other metal oxide fine particles can be produced.
前記第二のメタン化触媒の製造方法に用いられるＮａを含有しない沈殿剤としては炭酸水素アンモニウムが好ましい。沈殿剤として炭酸水素アンモニウムを用いることによって、Ｎａを含有していない共沈物を高収率（セリウム及び鉄族金属の仕込量の８０％以上）で得ることができる。 As the Na-free precipitant used in the second method for producing a methanation catalyst, ammonium bicarbonate is preferable. By using ammonium bicarbonate as a precipitant, a coprecipitate containing no Na can be obtained in high yield (80% or more of the charged amount of cerium and iron group metal).
〔メタンの製造方法〕
次に、本発明のメタンの製造方法について説明する。本発明のメタンの製造方法は、前記本発明のメタン化触媒に、二酸化炭素と水素との混合ガスを接触せしめることによって、メタンを製造する方法である。本発明のメタン化触媒を用いることによって、低温（例えば、２５０℃以下）であっても二酸化炭素と水素とから高収率でメタンを製造することができる。
[Methane production method]
Next, the method for producing methane of the present invention will be described. The method for producing methane of the present invention is a method for producing methane by bringing a mixed gas of carbon dioxide and hydrogen into contact with the methanation catalyst of the present invention. By using the methanation catalyst of the present invention, methane can be produced in high yield from carbon dioxide and hydrogen even at a low temperature (for example, 250 ° C. or lower).
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.
（実施例１）
先ず、得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が２０質量％、セリア（ＣｅＯ２）の含有量が８０質量％となるように、イオン交換水に硝酸ニッケル六水和物（和光純薬工業株式会社製）及び硝酸セリウム六水和物（和光純薬工業株式会社製）を溶解してニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した。この前駆体水溶液に、攪拌しながら、Ｎｉ＋及びＣｅ２＋を水酸化物の状態で沈殿させるために必要な量の１．３倍の水酸化ナトリウム（ＮａＯＨ）を含有する沈殿剤水溶液を３０分間かけて滴下した後、７０℃で１時間加熱し、次いで、一晩静置して共沈物を生成させた。その後、ろ過と６０℃の温水での洗浄とを７回繰り返して共沈物中のＮａ＋を除去した。得られた精製物を１１０℃で１２時間乾燥した後、大気中、４５０℃で２時間焼成して、ＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Example 1)
First, nickel nitrate hexahydrate (Wako Pure Chemical Industries, Ltd.) was added to ion-exchanged water so that the content of nickel oxide (NiO) in the obtained catalyst was 20% by mass and the content of ceria (CeO 2 ) was 80% by mass. By dissolving cerium nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) and cerium nitrate hexahydrate, a precursor aqueous solution containing nickel ions (Ni + ) and cerium ions (Ce 2+ ) was prepared. An aqueous solution of a precipitant containing 1.3 times the amount of sodium hydroxide (NaOH) required for precipitating Ni + and Ce 2+ in a hydroxide state was added to the aqueous precursor solution with stirring for 30 minutes. After that, the mixture was heated at 70 ° C. for 1 hour, and then allowed to stand overnight to form a coprecipitate. Thereafter, filtration and washing with warm water at 60 ° C. were repeated seven times to remove Na + in the coprecipitate. The obtained purified product was dried at 110 ° C. for 12 hours, and then calcined at 450 ° C. for 2 hours in the air to obtain a NiO—CeO 2 coprecipitated catalyst powder.
（実施例２）
得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が３０質量％、セリア（ＣｅＯ２）の含有量が７０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した以外は実施例１と同様にしてＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Example 2)
Nickel ions (Ni + ) and cerium ions (Ce 2+ ) are contained so that the content of nickel oxide (NiO) in the obtained catalyst is 30% by mass and the content of ceria (CeO 2 ) is 70% by mass. except that the precursor solution was prepared to give the NiO-CeO 2 coprecipitated catalyst powder in the same manner as in example 1.
（実施例３）
得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が４０質量％、セリア（ＣｅＯ２）の含有量が６０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した以外は実施例１と同様にしてＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Example 3)
Nickel ions (Ni + ) and cerium ions (Ce 2+ ) are contained so that the content of nickel oxide (NiO) in the obtained catalyst is 40% by mass and the content of ceria (CeO 2 ) is 60% by mass. except that the precursor solution was prepared to give the NiO-CeO 2 coprecipitated catalyst powder in the same manner as in example 1.
（実施例４）
得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が５０質量％、セリア（ＣｅＯ２）の含有量が５０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した以外は実施例１と同様にしてＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Example 4)
Nickel ions (Ni + ) and cerium ions (Ce 2+ ) are contained so that the content of nickel oxide (NiO) in the obtained catalyst is 50% by mass and the content of ceria (CeO 2 ) is 50% by mass. except that the precursor solution was prepared to give the NiO-CeO 2 coprecipitated catalyst powder in the same manner as in example 1.
（実施例５）
得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が６０質量％、セリア（ＣｅＯ２）の含有量が４０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した以外は実施例１と同様にしてＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Example 5)
Nickel ions (Ni + ) and cerium ions (Ce 2+ ) are contained so that the content of nickel oxide (NiO) and the content of ceria (CeO 2 ) in the obtained catalyst are 60% by mass and 40% by mass, respectively. except that the precursor solution was prepared to give the NiO-CeO 2 coprecipitated catalyst powder in the same manner as in example 1.
（実施例６）
得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が４０質量％、セリア（ＣｅＯ２）の含有量が６０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製し、また、沈殿剤水溶液として、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を炭酸塩の状態で沈殿させるために必要な量の１．２倍の炭酸ナトリウムを含有する沈殿剤水溶液を用いた以外は実施例１と同様にしてＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Example 6)
Nickel ions (Ni + ) and cerium ions (Ce 2+ ) are contained so that the content of nickel oxide (NiO) in the obtained catalyst is 40% by mass and the content of ceria (CeO 2 ) is 60% by mass. An aqueous solution of a precursor to be prepared is prepared, and as an aqueous solution of a precipitant, sodium carbonate 1.2 times the amount necessary for precipitating nickel ions (Ni + ) and cerium ions (Ce 2 + ) in a carbonate state is prepared. except for using a precipitant aqueous solution containing got NiO-CeO 2 coprecipitated catalyst powder in the same manner as in example 1.
（実施例７）
先ず、実施例３と同様に、得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が４０質量％、セリア（ＣｅＯ２）の含有量が６０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した。この前駆体水溶液に、攪拌しながら、Ｎｉ＋及びＣｅ２＋を炭酸塩の状態で沈殿させるために必要な量の２．４倍の炭酸水素アンモニウムを含有する沈殿剤水溶液を３０分間かけて滴下した後、７０℃で１時間加熱し、次いで、一晩静置して共沈物を生成させた。その後、共沈物をろ過により回収し、１１０℃で１２時間乾燥した後、大気中、４５０℃で２時間焼成して、ＮｉＯ−ＣｅＯ２共沈触媒粉末を得た（収率：セリウム及びニッケルの仕込量の８１％）。
(Example 7)
First, as in Example 3, nickel ions (Ni + ) were added so that the content of nickel oxide (NiO) in the obtained catalyst was 40% by mass and the content of ceria (CeO 2 ) was 60% by mass. And a precursor aqueous solution containing cerium ions (Ce 2+ ). An aqueous solution of a precipitant containing 2.4 times the amount of ammonium bicarbonate required for precipitating Ni + and Ce 2+ in a carbonate state was added dropwise to the aqueous precursor solution over 30 minutes while stirring. Thereafter, the mixture was heated at 70 ° C. for 1 hour and then allowed to stand overnight to form a coprecipitate. Thereafter, the coprecipitate was collected by filtration, dried at 110 ° C. for 12 hours, and calcined at 450 ° C. for 2 hours in the air to obtain a NiO—CeO 2 coprecipitated catalyst powder (yield: cerium and nickel). 81% of the charged amount).
（比較例１）
先ず、硝酸セリウム六水和物（和光純薬工業株式会社製）にアンモニア水（和光純薬工業株式会社製）を添加してセリア前駆体の沈殿を生成させた後、１５０℃で５時間脱水処理を行い、さらに、４００℃で５時間仮焼して焼成することにより、平均粒子径が８．１ｎｍのセリア粉末を得た。
(Comparative Example 1)
First, ammonia water (manufactured by Wako Pure Chemical Industries, Ltd.) is added to cerium nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) to precipitate a ceria precursor, and then dehydrated at 150 ° C. for 5 hours. The resultant was subjected to a treatment, and further calcined at 400 ° C. for 5 hours to obtain a ceria powder having an average particle diameter of 8.1 nm.
次に、得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が２０質量％となるように、イオン交換水に硝酸ニッケル六水和物を溶解して前駆体水溶液を調製した。この前駆体水溶液に、得られる触媒中のセリア（ＣｅＯ２）の含有量が８０質量％となる量の前記セリア粉末を浸漬し、攪拌しながら蒸発乾固させた。得られた固形分を１１０℃で１２時間乾燥した後、大気中、４５０℃で２時間焼成して、ＮｉＯ／ＣｅＯ２担持触媒粉末を得た。 Next, nickel nitrate hexahydrate was dissolved in ion-exchanged water to prepare a precursor aqueous solution such that the content of nickel oxide (NiO) in the obtained catalyst was 20% by mass. The ceria powder in an amount such that the content of ceria (CeO 2 ) in the resulting catalyst was 80% by mass was immersed in this precursor aqueous solution, and evaporated to dryness with stirring. The obtained solid was dried at 110 ° C. for 12 hours, and then calcined at 450 ° C. for 2 hours in the air to obtain a NiO / CeO 2 supported catalyst powder.
（比較例２）
セリア粉末の代わりに、得られる触媒中のジルコニア（ＺｒＯ２）の含有量が８０質量％となる量のジルコニア粉末（第一稀元素化学工業株式会社製「ＲＣ１００」、粒子径：１．５〜４μｍ）を用いた以外は比較例１と同様にしてＮｉＯ／ＺｒＯ２担持触媒粉末を得た。
(Comparative Example 2)
Instead of ceria powder, zirconia powder (“RC100” manufactured by Daiichi Rare Element Chemical Co., Ltd., particle diameter: 1.5 to 10%) is used in an amount such that the content of zirconia (ZrO 2 ) in the obtained catalyst is 80% by mass. 4 μm) to obtain a NiO / ZrO 2 supported catalyst powder in the same manner as in Comparative Example 1.
（比較例３）
セリア粉末の代わりに、得られる触媒中のチタニア（ＴｉＯ２）の含有量が８０質量％となる量のチタニア粉末（石原産業株式会社製「ＴＴＯ−５１」、粒子径：１０〜３０ｎｍ）を用いた以外は比較例１と同様にしてＮｉＯ／ＴｉＯ２担持触媒粉末を得た。
(Comparative Example 3)
Instead of ceria powder, titania powder (“TTO-51” manufactured by Ishihara Sangyo Co., Ltd., particle diameter: 10 to 30 nm) is used in such an amount that the content of titania (TiO 2 ) in the obtained catalyst becomes 80% by mass. A NiO / TiO 2 -supported catalyst powder was obtained in the same manner as in Comparative Example 1 except for the above.
（比較例４）
セリア粉末の代わりに、得られる触媒中のアルミナ（Ａｌ２Ｏ３）の含有量が８０質量％となる量のアルミナ粉末（グレース・ダビソン社製「ＭＩ−３０７」、平均粒子径：１７μｍ）を用いた以外は比較例１と同様にしてＮｉＯ／Ａｌ２Ｏ３担持触媒粉末を得た。
(Comparative Example 4)
Instead of ceria powder, alumina powder (“MI-307” manufactured by Grace Davison, average particle diameter: 17 μm) having an alumina (Al 2 O 3 ) content of 80% by mass in the obtained catalyst was used. A NiO / Al 2 O 3 -supported catalyst powder was obtained in the same manner as in Comparative Example 1 except that the catalyst powder was used.
（比較例５）
前記共沈物の洗浄回数を３回に変更した以外は実施例１と同様にしてＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Comparative Example 5)
A NiO—CeO 2 coprecipitated catalyst powder was obtained in the same manner as in Example 1 except that the number of times of washing the coprecipitate was changed to three times.
（比較例６）
前記共沈物の洗浄回数を５回に変更した以外は実施例１と同様にしてＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Comparative Example 6)
A NiO—CeO 2 coprecipitated catalyst powder was obtained in the same manner as in Example 1, except that the number of times of washing the coprecipitate was changed to 5.
（比較例７）
得られる触媒中の酸化ニッケル（ＮｉＯ）の含有量が１０質量％、セリア（ＣｅＯ２）の含有量が９０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した以外は実施例１と同様にしてＮｉＯ−ＣｅＯ２共沈触媒粉末を得た。
(Comparative Example 7)
Nickel ions (Ni + ) and cerium ions (Ce 2+ ) are contained so that the content of nickel oxide (NiO) and the content of ceria (CeO 2 ) in the obtained catalyst become 10% by mass and 90% by mass, respectively. except that the precursor solution was prepared to give the NiO-CeO 2 coprecipitated catalyst powder in the same manner as in example 1.
（比較例８）
先ず、実施例４と同様に、目的とする触媒中の酸化ニッケル（ＮｉＯ）の含有量が５０質量％、セリア（ＣｅＯ２）の含有量が５０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した。この前駆体水溶液に、攪拌しながら、Ｎｉ＋及びＣｅ２＋を水酸化物の状態で沈殿させるために必要な量の１．３倍のアンモニア水を沈殿剤水溶液として３０分間かけて滴下した後、７０℃で１時間加熱し、次いで、一晩静置したが、沈殿は生成しなかった。
(Comparative Example 8)
First, as in Example 4, nickel ions (Ni + ) were added such that the content of nickel oxide (NiO) in the target catalyst was 50% by mass and the content of ceria (CeO 2 ) was 50% by mass. ) And cerium ions (Ce 2+ ). To this aqueous precursor solution, 1.3 times ammonia water, which is necessary for precipitating Ni + and Ce 2+ in a hydroxide state, was added dropwise as a precipitant aqueous solution over 30 minutes while stirring, Heated at 70 ° C. for 1 hour and then left overnight, no precipitate formed.
（比較例９）
先ず、実施例４と同様に、目的とする触媒中の酸化ニッケル（ＮｉＯ）の含有量が５０質量％、セリア（ＣｅＯ２）の含有量が５０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した。この前駆体水溶液に、攪拌しながら、Ｎｉ＋及びＣｅ２＋を水酸化物の状態で沈殿させるために必要な量の１．３倍のシュウ酸を含有する沈殿剤水溶液を３０分間かけて滴下した後、７０℃で１時間加熱し、次いで、一晩静置したところ、Ｃｅ２＋のみが沈殿してＮｉ＋は沈殿しなかったため、共沈物は得られなかった。
(Comparative Example 9)
First, as in Example 4, nickel ions (Ni + ) were added such that the content of nickel oxide (NiO) in the target catalyst was 50% by mass and the content of ceria (CeO 2 ) was 50% by mass. ) And cerium ions (Ce 2+ ). An aqueous solution of a precipitant containing 1.3 times the amount of oxalic acid required to precipitate Ni + and Ce 2+ in the form of a hydroxide was added dropwise to the aqueous precursor solution over 30 minutes while stirring. Thereafter, the mixture was heated at 70 ° C. for 1 hour and then allowed to stand overnight. As a result, only Ce 2+ precipitated and Ni + did not precipitate, and thus no coprecipitate was obtained.
（比較例１０）
先ず、実施例４と同様に、目的とする触媒中の酸化ニッケル（ＮｉＯ）の含有量が５０質量％、セリア（ＣｅＯ２）の含有量が５０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した。この前駆体水溶液に、攪拌しながら、Ｎｉ＋及びＣｅ２＋を水酸化物の状態で沈殿させるために必要な量の１．３倍のシュウ酸アンモニウムを含有する沈殿剤水溶液を３０分間かけて滴下した後、７０℃で１時間加熱し、次いで、一晩静置したところ、Ｃｅ２＋のみが沈殿してＮｉ＋は沈殿しなかったため、共沈物は得られなかった。
(Comparative Example 10)
First, as in Example 4, nickel ions (Ni + ) were added such that the content of nickel oxide (NiO) in the target catalyst was 50% by mass and the content of ceria (CeO 2 ) was 50% by mass. ) And cerium ions (Ce 2+ ). An aqueous solution of a precipitant containing 1.3 times the amount of ammonium oxalate necessary for precipitating Ni + and Ce 2+ in the form of hydroxide was added dropwise to the aqueous solution of the precursor over 30 minutes while stirring. After heating at 70 ° C. for 1 hour and then standing overnight, no coprecipitate was obtained because only Ce 2+ precipitated and Ni + did not precipitate.
（比較例１１）
先ず、実施例４と同様に、目的とする触媒中の酸化ニッケル（ＮｉＯ）の含有量が５０質量％、セリア（ＣｅＯ２）の含有量が５０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した。この前駆体水溶液に、攪拌しながら、Ｎｉ＋及びＣｅ２＋を水酸化物の状態で沈殿させるために必要な量の１．３倍のクエン酸を含有する沈殿剤水溶液を３０分間かけて滴下した後、７０℃で１時間加熱し、次いで、一晩静置したが、沈殿は生成しなかった。
(Comparative Example 11)
First, as in Example 4, nickel ions (Ni + ) were added such that the content of nickel oxide (NiO) in the target catalyst was 50% by mass and the content of ceria (CeO 2 ) was 50% by mass. ) And cerium ions (Ce 2+ ). An aqueous solution of a precipitant containing 1.3 times the amount of citric acid required to precipitate Ni + and Ce 2+ in the form of a hydroxide was added dropwise to the aqueous solution of the precursor over 30 minutes while stirring. Thereafter, the mixture was heated at 70 ° C. for 1 hour and then allowed to stand overnight, but no precipitate was formed.
（比較例１２）
先ず、実施例４と同様に、目的とする触媒中の酸化ニッケル（ＮｉＯ）の含有量が５０質量％、セリア（ＣｅＯ２）の含有量が５０質量％となるように、ニッケルイオン（Ｎｉ＋）及びセリウムイオン（Ｃｅ２＋）を含有する前駆体水溶液を調製した。この前駆体水溶液に、攪拌しながら、Ｎｉ＋及びＣｅ２＋を水酸化物の状態で沈殿させるために必要な量の１．３倍の尿素を含有する沈殿剤水溶液を３０分間かけて滴下した後、８５℃以上で３０分間加熱し、次いで、一晩静置したが、セリウムの沈殿物が僅かに生成したのみであった（収率：セリウム仕込み量の１％以下）。
(Comparative Example 12)
First, as in Example 4, nickel ions (Ni + ) were added such that the content of nickel oxide (NiO) in the target catalyst was 50% by mass and the content of ceria (CeO 2 ) was 50% by mass. ) And cerium ions (Ce 2+ ). An aqueous solution of a precipitant containing 1.3 times the amount of urea required for precipitating Ni + and Ce 2+ in the form of hydroxide was added dropwise to this aqueous precursor solution over 30 minutes while stirring. After heating at 85 ° C. or higher for 30 minutes and then standing overnight, only a small amount of cerium precipitate was formed (yield: 1% or less of the charged amount of cerium).
＜鉄族金属元素の含有量及びその分散性＞
先ず、実施例１〜７及び比較例１、７で得られた各触媒粉末について、触媒全体のＮｉ含有量（単位：質量％）を、走査型蛍光Ｘ線分析装置（ＸＲＦ、株式会社リガク製「ＺＳＸ Ｐｒｉｍｕｓ」）を用いて測定した。その結果を表１に示す。
<Content of iron group metal element and its dispersibility>
First, for each of the catalyst powders obtained in Examples 1 to 7 and Comparative Examples 1 and 7, the Ni content (unit: mass%) of the entire catalyst was measured using a scanning X-ray fluorescence analyzer (XRF, manufactured by Rigaku Corporation). "ZSX Primus"). Table 1 shows the results.
次に、実施例１〜７及び比較例１、７で得られた各触媒粉末０．０１ｇを導電性カーボンテープ上に塗布してＥＤＸ分析用試験片（５ｍｍ×５ｍｍ×０．１５ｍｍ）を作製した。この試験片の表面において無作為に２０点の測定領域（１μｍφ×１μｍ深さ）を抽出し、走査型電子顕微鏡（ＳＥＭ、株式会社日立ハイテクノロジーズ製「ＳＵ−３６００Ｎ」）に装着したエネルギー分散型Ｘ線分光分析装置（ＥＤＸ、アメテック社製「ＥＤＡＸ」）を用いて各測定領域内の元素分析を行い、各測定領域のＮｉ含有量（単位：質量％）を求めた。得られた各測定領域のＮｉ含有量に基づいて、ＳＥＭ−ＥＤＸ分析法により測定したＮｉ含有量の平均値、並びに、ＸＲＦ分析法により測定した触媒全体のＮｉ含有量に対する、２０点の前記測定領域についてＳＥＭ−ＥＤＸ分析法により測定したＮｉ含有量の標準偏差を算出した。その結果を表１に示す。 Next, 0.01 g of each catalyst powder obtained in Examples 1 to 7 and Comparative Examples 1 and 7 was applied on a conductive carbon tape to prepare a test piece for EDX analysis (5 mm × 5 mm × 0.15 mm). did. Twenty measurement areas (1 μmφ × 1 μm depth) were randomly extracted from the surface of the test piece, and the energy dispersive type was mounted on a scanning electron microscope (SEM, “SU-3600N” manufactured by Hitachi High-Technologies Corporation). Elemental analysis was performed in each measurement region using an X-ray spectrometer (EDX, "EDAX" manufactured by Ametech), and the Ni content (unit: mass%) in each measurement region was determined. Based on the obtained Ni content of each measurement region, the average of the Ni content measured by the SEM-EDX analysis method, and the above-described measurement at 20 points with respect to the Ni content of the entire catalyst measured by the XRF analysis method The standard deviation of the Ni content measured by SEM-EDX analysis for the region was calculated. Table 1 shows the results.
表１に示したように、共沈法により製造したＮｉＯ−ＣｅＯ２触媒粉末（実施例１〜７及び比較例７）は、Ｎｉ含有量の標準偏差が４以下と小さく、ＮｉＯ微粒子が均一に分散したもの（ＮｉＯ微粒子の分散性が高いもの）であることが確認された。一方、含浸法によりＮｉＯを担持せしめたＮｉＯ／ＣｅＯ２触媒粉末（比較例１）は、Ｎｉ含有量の標準偏差が７．４２と大きく、ＮｉＯ微粒子が不均一に分散したもの（ＮｉＯ微粒子の分散性が低いもの）であることがわかった。 As shown in Table 1, the NiO—CeO 2 catalyst powder (Examples 1 to 7 and Comparative Example 7) produced by the coprecipitation method had a small standard deviation of the Ni content of 4 or less, and the NiO fine particles were uniform. It was confirmed that the particles were dispersed (the particles had high dispersibility of the NiO particles). On the other hand, the NiO / CeO 2 catalyst powder supporting NiO by the impregnation method (Comparative Example 1) has a large standard deviation of the Ni content of 7.42, and the NiO fine particles are dispersed unevenly (dispersion of the NiO fine particles). Is low).
＜鉄族金属元素含有微粒子及びセリア微粒子の平均粒子径＞
実施例１、３、５及び比較例１〜４、７で得られた各触媒粉末中のＮｉＯ微粒子及びＣｅＯ２微粒子の平均粒子径を、粉末Ｘ線回折装置（ＸＲＤ、株式会社リガク製「ＵｌｔｉｍａＩＶ」）を用いて測定した。その結果を表２に示す。なお、比較例７で得られたＮｉＯ−ＣｅＯ２共沈触媒粉末については、ＮｉＯの含有量が少なかったため、ＸＲＤ分析によるＮｉＯ微粒子の平均粒子径の測定は困難であった。
<Average particle diameter of iron group metal element-containing fine particles and ceria fine particles>
The average particle diameter of the NiO fine particles and the CeO 2 fine particles in each of the catalyst powders obtained in Examples 1, 3, 5 and Comparative Examples 1 to 4, and 7 was measured using a powder X-ray diffractometer (XRD, “Ultima IV” manufactured by Rigaku Corporation). "). Table 2 shows the results. The NiO—CeO 2 coprecipitated catalyst powder obtained in Comparative Example 7 had a low NiO content, so that it was difficult to measure the average particle size of the NiO fine particles by XRD analysis.
表２に示したように、共沈法により製造したＮｉＯ−ＣｅＯ２触媒粉末（実施例１、３、５）は、含浸法によりＮｉＯを担持せしめた触媒粉末（比較例１〜４）に比べて、平均粒子径が小さいＮｉＯ微粒子を含有するものであることがわかった。 As shown in Table 2, the NiO—CeO 2 catalyst powder manufactured by the coprecipitation method (Examples 1, 3, and 5) was compared with the catalyst powder supporting NiO by the impregnation method (Comparative Examples 1 to 4). Thus, it was found that the particles contained NiO fine particles having a small average particle diameter.
＜触媒性能評価試験１＞
実施例１及び比較例１〜６で得られた各触媒粉末０．５ｍｌを内径６ｍｍのステンレス製反応管に充填し、この触媒にＨ２（１００ｍｌ／ｍｉｎ）＋Ｎ２（３７５ｍｌ／ｍｉｎ）の混合ガスを触媒入りガス温度３００℃で流通させて還元前処理を行なった。次いで、ＣＯ２（２５ｍｌ／ｍｉｎ）＋Ｈ２（１００ｍｌ／ｍｉｎ）＋Ｎ２（３７５ｍｌ／ｍｉｎ）の混合ガスを流通させ、触媒入りガス温度２２５℃における触媒出ガスのＣＯ２濃度及びＣＨ４濃度をガスクロマトグラフィ（株式会社島津製作所製「ＧＣ−１４Ｂ」）を用いて測定した。その結果、実施例１及び比較例１〜６で得られた、いずれの触媒粉末においても、ＣＨ４以外の炭化水素（ＨＣ）類の生成は確認されず、また、ＣＨ４の生成量はＣＯ２の減少量にほぼ対応していたことから、減少したＣＯ２のほぼ全量がＣＨ４に転化したことが確認された。そこで、各触媒粉末について、触媒入りガス温度２２５℃におけるＣＯ２転化率を算出した。その結果を表３〜表４に示す。
<Catalyst performance evaluation test 1>
0.5 ml of each catalyst powder obtained in Example 1 and Comparative Examples 1 to 6 was filled into a stainless steel reaction tube having an inner diameter of 6 mm, and the catalyst was mixed with H 2 (100 ml / min) + N 2 (375 ml / min). The gas was circulated at a catalyst-containing gas temperature of 300 ° C. to perform a pre-reduction treatment. Then, a mixed gas of CO 2 (25 ml / min) + H 2 (100 ml / min) + N 2 (375 ml / min) was passed, and the CO 2 concentration and CH 4 concentration of the catalyst exit gas at a catalyst-containing gas temperature of 225 ° C. were measured. The measurement was performed using chromatography (“GC-14B” manufactured by Shimadzu Corporation). As a result, in any of the catalyst powders obtained in Example 1 and Comparative Examples 1 to 6, generation of hydrocarbons (HC) other than CH 4 was not confirmed, and the generation amount of CH 4 was CO. Since it almost corresponded to the decrease amount of 2 , it was confirmed that almost all of the reduced CO 2 was converted to CH 4 . Therefore, for each catalyst powder, the CO 2 conversion at a catalyst-containing gas temperature of 225 ° C. was calculated. The results are shown in Tables 3 and 4.
＜触媒性能評価試験２＞
実施例１〜７及び比較例７で得られた各触媒粉末０．３７５ｍｌを内径６ｍｍのステンレス製反応管に充填し、この触媒にＨ２（１００ｍｌ／ｍｉｎ）＋Ｎ２（３７５ｍｌ／ｍｉｎ）の混合ガスを触媒入りガス温度３００℃で流通させて還元前処理を行なった。次いで、ＣＯ２（２５ｍｌ／ｍｉｎ）＋Ｈ２（１００ｍｌ／ｍｉｎ）の混合ガスを流通させ、触媒入りガス温度２２５℃における触媒出ガスのＣＯ２濃度及びＣＨ４濃度をガスクロマトグラフィ（株式会社島津製作所製「ＧＣ−１４Ｂ」）を用いて測定した。その結果、実施例１〜７及び比較例７で得られた、いずれの触媒粉末においても、ＣＨ４以外の炭化水素（ＨＣ）類の生成は確認されず、また、ＣＨ４の生成量はＣＯ２の減少量にほぼ対応していたことから、減少したＣＯ２のほぼ全量がＣＨ４に転化したことが確認された。そこで、各触媒粉末について、触媒入りガス温度２２５℃におけるＣＯ２転化率を算出した。その結果を表５〜表６に示す。
<Catalyst performance evaluation test 2>
0.375 ml of each catalyst powder obtained in Examples 1 to 7 and Comparative Example 7 was filled in a stainless steel reaction tube having an inner diameter of 6 mm, and the catalyst was mixed with H 2 (100 ml / min) + N 2 (375 ml / min). The gas was circulated at a catalyst-containing gas temperature of 300 ° C. to perform a pre-reduction treatment. Next, a mixed gas of CO 2 (25 ml / min) + H 2 (100 ml / min) was passed, and the CO 2 concentration and CH 4 concentration of the catalyst exit gas at a catalyst-containing gas temperature of 225 ° C. were measured by gas chromatography (manufactured by Shimadzu Corporation). "GC-14B"). As a result, in any of the catalyst powders obtained in Examples 1 to 7 and Comparative Example 7, generation of hydrocarbons (HC) other than CH 4 was not confirmed, and the generation amount of CH 4 was CO. Since it almost corresponded to the decrease amount of 2 , it was confirmed that almost all of the reduced CO 2 was converted to CH 4 . Therefore, for each catalyst powder, the CO 2 conversion at a catalyst-containing gas temperature of 225 ° C. was calculated. The results are shown in Tables 5 and 6.
＜触媒中のＮａ含有量＞
実施例１及び比較例５〜６で得られた各触媒粉末について、触媒全体のＮａ含有量を、走査型蛍光Ｘ線分析装置（ＸＲＦ、株式会社リガク製「ＺＳＸ Ｐｒｉｍｕｓ」）を用いて測定した。その結果を表４に示す。
<Na content in catalyst>
For each of the catalyst powders obtained in Example 1 and Comparative Examples 5 to 6, the Na content of the entire catalyst was measured using a scanning X-ray fluorescence spectrometer (XRF, “ZSX Primus” manufactured by Rigaku Corporation). . Table 4 shows the results.
表３に示したように、共沈法により製造され、ＮｉＯ微粒子の分散性が高いＮｉＯ−ＣｅＯ２共沈触媒粉末（実施例１）は、含浸法により製造され、ＮｉＯ微粒子の分散性が低いＮｉＯ／ＣｅＯ２担持触媒粉末（比較例１〜４）に比べて、ＣＯ２の転化率が高く、メタン化触媒活性が高いことがわかった。 As shown in Table 3, the NiO—CeO 2 coprecipitated catalyst powder (Example 1) manufactured by the coprecipitation method and having high dispersibility of the NiO fine particles was manufactured by the impregnation method, and the dispersibility of the NiO fine particles was low. It was found that the conversion rate of CO 2 was higher and the methanation catalyst activity was higher than the NiO / CeO 2 supported catalyst powder (Comparative Examples 1 to 4).
表４に示したように、Ｎａ含有量が１ａｔ％以下のＮｉＯ−ＣｅＯ２共沈触媒粉末（実施例１）は、Ｎａ含有量が６．２ａｔ％又は１．８ａｔ％のＮｉＯ−ＣｅＯ２共沈触媒粉末（比較例５、６）に比べて、ＣＯ２の転化率が高く、メタン化触媒活性が高いことがわかった。 As shown in Table 4, the NiO—CeO 2 coprecipitated catalyst powder having an Na content of 1 at% or less (Example 1) had a Na content of 6.2 at% or 1.8 at% for NiO—CeO 2 . It was found that the conversion rate of CO 2 was higher and the methanation catalyst activity was higher than the precipitated catalyst powder (Comparative Examples 5 and 6).
表５に示したように、触媒全体のＮｉ含有量が１５質量％以上のＮｉＯ−ＣｅＯ２共沈触媒粉末（実施例１〜５）は、触媒全体のＮｉ含有量が９．３質量％のＮｉＯ−ＣｅＯ２共沈触媒粉末（比較例７）に比べて、ＣＯ２の転化率が高く、メタン化触媒活性が高いことがわかった。 As shown in Table 5, Ni content of 15 mass% or more NiO-CeO 2 coprecipitated catalyst powder of the entire catalyst (Examples 1-5) is, Ni content of the entire catalyst is 9.3 wt% It was found that the conversion rate of CO 2 was higher and the methanation catalyst activity was higher than that of the NiO—CeO 2 coprecipitated catalyst powder (Comparative Example 7).
表６に示したように、水酸化ナトリウム（実施例３）、炭酸ナトリウム（実施例６）、及び炭酸水素アンモニウム（実施例７）のいずれの沈殿剤を用いた場合でも、ＣＯ２の転化率が高く、メタン化触媒活性が高いＮｉＯ−ＣｅＯ２共沈触媒粉末が得られることがわかった。 As shown in Table 6, the conversion rate of CO 2 was obtained using any of the precipitants sodium hydroxide (Example 3), sodium carbonate (Example 6), and ammonium bicarbonate (Example 7). It has been found that a NiO—CeO 2 coprecipitated catalyst powder having a high methanation catalytic activity and a high methanation catalyst activity is obtained.
以上説明したように、本発明によれば、低温（例えば、２５０℃以下）であっても高い触媒活性を示すメタン化触媒を得ることが可能となる。したがって、本発明のメタンの製造方法は、このようなメタン化触媒を用いているため、低温（例えば、２５０℃以下）においても二酸化炭素と水素とから高収率でメタンを製造することができる方法として有用である。 As described above, according to the present invention, it is possible to obtain a methanation catalyst having high catalytic activity even at a low temperature (for example, 250 ° C. or lower). Therefore, in the method for producing methane of the present invention, since such a methanation catalyst is used, methane can be produced in high yield from carbon dioxide and hydrogen even at a low temperature (for example, 250 ° C. or lower). Useful as a method.
Claims (7)
前記メタン化触媒全体について蛍光Ｘ線分析法により測定した鉄族金属元素の含有量がＣｅと鉄族金属元素との合計量に対して１５〜８０質量％であり、
前記メタン化触媒全体について蛍光Ｘ線分析法により測定した鉄族金属元素の含有量に対する、前記メタン化触媒において無作為に抽出した２０点の測定領域（１μｍφ×１μｍ深さ）についてエネルギー分散型Ｘ線分光分析法により測定した鉄族金属元素の含有量の標準偏差が４以下であり、
Ｎａ含有量が１ａｔ％以下である、
ことを特徴とするメタン化触媒。 A methanation catalyst containing ceria fine particles and iron group metal element-containing fine particles composed of an iron group metal or an oxide thereof,
The content of the iron group metal element measured by X-ray fluorescence analysis for the entire methanation catalyst is 15 to 80% by mass based on the total amount of Ce and the iron group metal element,
With respect to the content of the iron group metal element measured by the fluorescent X-ray analysis method for the entire methanation catalyst, energy dispersive X-ray analysis was performed for 20 measurement areas (1 μmφ × 1 μm depth) randomly extracted in the methanation catalyst. The standard deviation of the iron group metal element content measured by X-ray spectroscopy is 4 or less,
Na content is 1 at% or less,
A methanation catalyst characterized by the above-mentioned.
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| WO2024181400A1 (en) * | 2023-02-28 | 2024-09-06 | 三井金属鉱業株式会社 | Method for producing methane from material gas containing carbon dioxide gas and hydrogen gas, and catalyst for methanation of carbon dioxide |
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| JPH08127544A (en) * | 1994-10-31 | 1996-05-21 | Agency Of Ind Science & Technol | Production of methane from carbon dioxide and hydrogen |
| JP2008056539A (en) * | 2006-08-31 | 2008-03-13 | Catalysts & Chem Ind Co Ltd | Carbon monoxide methanation method |
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| JPS5791740A (en) * | 1980-07-16 | 1982-06-08 | Dyson Refractories | Improved catalyst of hydrocarbon and its manufacture |
| JPH08127544A (en) * | 1994-10-31 | 1996-05-21 | Agency Of Ind Science & Technol | Production of methane from carbon dioxide and hydrogen |
| JP2008056539A (en) * | 2006-08-31 | 2008-03-13 | Catalysts & Chem Ind Co Ltd | Carbon monoxide methanation method |
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| CN114471512A (en) * | 2020-10-27 | 2022-05-13 | 中国石油天然气股份有限公司 | Low-temperature methanation catalyst and preparation method thereof |
| WO2024181400A1 (en) * | 2023-02-28 | 2024-09-06 | 三井金属鉱業株式会社 | Method for producing methane from material gas containing carbon dioxide gas and hydrogen gas, and catalyst for methanation of carbon dioxide |
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