JP2023126494A - Ammonia synthesis catalyst - Google Patents
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 109
- 239000003054 catalyst Substances 0.000 title claims abstract description 103
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 53
- 238000003786 synthesis reaction Methods 0.000 title description 48
- 230000015572 biosynthetic process Effects 0.000 title description 44
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 14
- 238000006243 chemical reaction Methods 0.000 claims abstract description 13
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 13
- 239000001257 hydrogen Substances 0.000 claims abstract description 10
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 19
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 230000002194 synthesizing effect Effects 0.000 claims description 7
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 2
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 abstract description 11
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 abstract description 10
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 4
- 230000003197 catalytic effect Effects 0.000 abstract description 4
- 229910002788 Ru-CeO2 Inorganic materials 0.000 abstract description 3
- 230000000694 effects Effects 0.000 description 48
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 34
- 239000007864 aqueous solution Substances 0.000 description 29
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 27
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 12
- 238000001354 calcination Methods 0.000 description 11
- 239000011148 porous material Substances 0.000 description 11
- 239000000243 solution Substances 0.000 description 11
- 239000011777 magnesium Substances 0.000 description 10
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 238000002156 mixing Methods 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 239000012299 nitrogen atmosphere Substances 0.000 description 8
- YLPJWCDYYXQCIP-UHFFFAOYSA-N nitroso nitrate;ruthenium Chemical compound [Ru].[O-][N+](=O)ON=O YLPJWCDYYXQCIP-UHFFFAOYSA-N 0.000 description 7
- 230000001376 precipitating effect Effects 0.000 description 7
- 230000002378 acidificating effect Effects 0.000 description 6
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 6
- 239000002244 precipitate Substances 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 6
- 238000010304 firing Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 4
- 239000003929 acidic solution Substances 0.000 description 4
- 238000000975 co-precipitation Methods 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910002651 NO3 Inorganic materials 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001739 density measurement Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- 239000006069 physical mixture Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
- Y02P20/133—Renewable energy sources, e.g. sunlight
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
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Abstract
Description
本発明はＮ２とＨ２からＮＨ３を合成するアンモニア合成触媒に関する。 The present invention relates to an ammonia synthesis catalyst for synthesizing NH3 from N2 and H2 .
Ｎ２とＨ２からＮＨ３を合成する方法として、Ｆｅ３Ｏ４－Ａｌ２Ｏ３－Ｋ２ＯなどのＦｅ系触媒を用い、２３－３５ＭＰａ、約５００℃程度の高温高圧で反応を行うハーバー・ボッシュ法が知られている。
その後、Ｒｕ－ＣｅＯ２触媒を用いて、より低温低圧の温和な条件で反応を行う方法が開発された（特許文献１、２）。この方法で用いる触媒は、硝酸セリウムを、アンモニア水溶液を用いてアルカリ性条件下で沈殿させ、６００℃程度で焼成して得たＣｅＯ２に、Ｒｕカルボニルの溶液を含浸し、水素還元することで作製され、これにより、２００～６００℃程度の温度、１～２０気圧程度の低圧でのＮＨ３合成を実現している。
As a method for synthesizing NH 3 from N 2 and H 2 , a Fe-based catalyst such as Fe 3 O 4 -Al 2 O 3 -K 2 O is used, and the reaction is carried out at high temperature and pressure of about 23-35 MPa and about 500°C. The Haber-Bosch method is known.
Subsequently, a method was developed in which a Ru-CeO 2 catalyst was used to carry out the reaction under milder conditions at lower temperatures and pressures (
Ｒｕ－ＣｅＯ２は、特許文献１、２に示されるように、アンモニア合成触媒として特許が出願されているが、ＣｅＯ２の物理的・化学的状態が異なることによってＲｕ－ＣｅＯ２の触媒性能は全く異なり、高いアンモニア合成活性を再現性よく引き出す調製法を示した特許等の文献はない。
また、Ｒｕ－ＣｅＯ２はＲｕおよびＣｅＯ２ともに高コストな素材であり、どちらの元素の使用量も低減することが望まれる。
本発明は、高いアンモニア合成活性を得ることができるＲｕ－ＣｅＯ２触媒の調製法を提供すること、およびＲｕ－ＣｅＯ２触媒におけるＣｅＯ２使用量削減に対して効果的な触媒調製法を提供することを課題とする。
As shown in
Furthermore, both Ru and CeO 2 are high-cost materials, and it is desirable to reduce the amount of both elements used.
The present invention provides a method for preparing a Ru-CeO 2 catalyst that can obtain high ammonia synthesis activity, and a method for preparing a catalyst that is effective for reducing the amount of CeO 2 used in the Ru-CeO 2 catalyst. That is the issue.
本発明者らは、硝酸セリウムを水酸化カリウムもしくはアンモニアの水溶液を用いて沈殿・焼成して作製したＣｅＯ２に強酸性のニトロシル硝酸ルテニウム（Ｒｕ（ＮＯ）（ＮＯ３）３）の溶液を含浸することにより作製したＲｕ－ＣｅＯ２触媒が、従来のＲｕカルボニルを用いて作製した触媒と比べて、高いアンモニア合成活性を有することを見出した。これに対し、硝酸セリウムを水酸化ナトリウムやクエン酸により沈殿・焼成して作製したＣｅＯ２を用いた場合は、アンモニア合成活性は、従来のＲｕカルボニルを用いて作製した触媒よりも低かった。
また、アンモニア合成活性は、ＣｅＯ２の焼成温度によっても変化し、水酸化カリウムにより沈殿させたＣｅＯ２を用いた触媒では、６００℃で焼成したものが最も活性が高かった。
The present inventors impregnated CeO 2 , which was prepared by precipitating and calcining cerium nitrate with an aqueous solution of potassium hydroxide or ammonia, with a solution of strongly acidic ruthenium nitrosyl nitrate (Ru(NO)(NO 3 ) 3 ). It has been found that a Ru-CeO 2 catalyst prepared by this method has higher ammonia synthesis activity than a conventional catalyst prepared using Ru carbonyl. On the other hand, when CeO 2 prepared by precipitating and calcining cerium nitrate with sodium hydroxide or citric acid was used, the ammonia synthesis activity was lower than that of a conventional catalyst prepared using Ru carbonyl.
Furthermore, the ammonia synthesis activity also changed depending on the firing temperature of CeO 2 , and among catalysts using CeO 2 precipitated with potassium hydroxide, the one fired at 600° C. had the highest activity.
ＣｅＯ２は塩基性の担体であり、強酸性の溶液で処理するとその表面が一部溶解する。このことが、強酸性のニトロシル硝酸ルテニウムの溶液をＣｅＯ２に含浸することにより作製した本発明の触媒が高いアンモニア合成活性を有することと関連しているのではないかとの想定の下に、本発明者らは、ＣｅＯ２を強酸性の溶液で処理したときに生じるＣｅＯ２担体の表面の状態を模するものとして、結晶性のＣｅＯ２に硝酸セリウム水溶液を含浸させ、焼成することで、結晶性ＣｅＯ２の表面に非晶質のＣｅＯ２を、種々のＡｍｏ（非晶質）／Ｃｒｙ（結晶質）の比率で担持した担体を作製し、これにＲｕを担持した触媒を用いてアンモニア合成反応を行った。
その結果、Ａｍｏの比率を高めるにつれて担体の表面積及び細孔容積は大きくなるが、触媒のアンモニア合成活性も同様に一律に高まるわけではなく、Ａｍｏ／Ｃｒｙ比が１である場合をピークに、それ以上Ａｍｏの比率を高めるとアンモニア合成活性がかえって低くなることを見出した。
硝酸セリウムを水酸化カリウムもしくはアンモニアの水溶液を用いて沈殿・焼成して作製したＣｅＯ２に強酸性のニトロシル硝酸ルテニウムの溶液を含浸することにより作製したＲｕ－ＣｅＯ２触媒においては、ＣｅＯ２担体の表面が、上述のＡｍｏ／Ｃｒｙ比が１である場合と類似する構造を有しているものと推察される。
CeO 2 is a basic carrier, and its surface partially dissolves when treated with a strongly acidic solution. Based on the assumption that this may be related to the high ammonia synthesis activity of the catalyst of the present invention prepared by impregnating CeO 2 with a solution of strongly acidic ruthenium nitrosyl nitrate, the present invention was conducted. The inventors imitated the surface state of a CeO 2 carrier that occurs when CeO 2 is treated with a strongly acidic solution, by impregnating crystalline CeO 2 with an aqueous cerium nitrate solution and firing it. Ammonia synthesis was carried out using a catalyst supporting Ru on the surface of amorphous CeO 2 with various Amo (amorphous)/Cry (crystalline) ratios . The reaction was carried out.
As a result, as the ratio of Amo increases, the surface area and pore volume of the carrier increase, but the ammonia synthesis activity of the catalyst also does not increase uniformly. It has been found that increasing the ratio of Amo actually lowers the ammonia synthesis activity.
In the Ru-CeO 2 catalyst prepared by impregnating CeO 2 prepared by precipitating and calcining cerium nitrate with an aqueous solution of potassium hydroxide or ammonia with a solution of strongly acidic ruthenium nitrosyl nitrate, It is presumed that the surface has a structure similar to that in the case where the Amo/Cry ratio is 1 as described above.
Ｒｕ－ＣｅＯ２触媒に用いられるＲｕもＣｅＯ２も高価な材料である。本発明者らは、Ｒｕ－ＣｅＯ２触媒にＭｇＯを混合することで、ＭｇＯの混合量に応じてＲｕ－ＣｅＯ２触媒に含まれるＣｅＯ２の量を減らすことができ、ＣｅＯ２の量を減らさない場合と匹敵し、あるいはそれを上回るアンモニア合成活性が得られることを見出した。これにより、高価な材料であるＣｅＯ２の、同一のＲｕの量に対する使用量を抑えることができる。
同様の量のＲｕ、ＣｅＯ２およびＭｇＯを用いても、共沈や物理的混合により得られたＣｅＯ２およびＭｇＯの混合物にＲｕを担持した場合や、ＭｇＯ外表面にＣｅＯ２を担持した後、これにＲｕを担持した場合には、このような効果は見られないことから、このような効果を得るためには、ＲｕはＣｅＯ２に集約されて担持されている必要があるものと考えられる。
Both Ru and CeO 2 used in the Ru-CeO 2 catalyst are expensive materials. The present inventors have found that by mixing MgO into the Ru-CeO 2 catalyst, the amount of CeO 2 contained in the Ru-CeO 2 catalyst can be reduced according to the amount of MgO mixed, and the amount of CeO 2 can be reduced. It has been found that an ammonia synthesis activity comparable to or exceeding that without the ammonia synthesis activity can be obtained. This makes it possible to suppress the amount of CeO 2 , which is an expensive material, used for the same amount of Ru.
Even if similar amounts of Ru, CeO 2 and MgO are used, when Ru is supported on a mixture of CeO 2 and MgO obtained by coprecipitation or physical mixing, or after CeO 2 is supported on the outer surface of MgO, When Ru is supported on this, such an effect is not observed, so it is thought that in order to obtain such an effect, Ru must be supported in a concentrated manner on CeO2 . .
本発明者らは、さらに、Ｒｕ－ＣｅＯ２触媒において、モル比Ｒｕ／Ｆｅ＝５～２００の範囲でＦｅを添加することにより、Ｆｅを添加しない場合を上回るアンモニア合成活性が得られることを見出した。
具体的には、Ｆｅ（ＮＯ３）３水溶液を用いてＣｅＯ２にＦｅを含浸担持させ、焼成した後、得られたＦｅ／ＣｅＯ２にニトロシル硝酸ルテニウムの溶液を用いてＲｕを含浸担持し、水素還元する。
第二成分の添加により触媒活性が向上することは、他の触媒系においても観察されることがあるが、モル比Ｒｕ／Ｆｅ＝１００～２００などの少ない量のＦｅの共存によっても上記効果が得られることは、本発明の際立った効果であるといえる。
The present inventors further discovered that by adding Fe in the Ru-CeO 2 catalyst at a molar ratio of Ru/Fe = 5 to 200, ammonia synthesis activity exceeding that in the case of not adding Fe can be obtained. Ta.
Specifically, Fe is impregnated and supported on CeO 2 using an aqueous Fe(NO 3 ) 3 solution, and after firing, Ru is impregnated and supported on the obtained Fe/CeO 2 using a solution of ruthenium nitrosyl nitrate. Reduces hydrogen.
Although it has been observed in other catalyst systems that the catalytic activity is improved by the addition of a second component, the above effect can also be achieved by the coexistence of a small amount of Fe such as at a molar ratio of Ru/Fe = 100-200. This can be said to be a remarkable effect of the present invention.
本発明は、本発明者らが得た、これらの知見に基づいてなされたものであり、本出願は、具体的には、以下の発明を提供するものである。
〈１〉担体として酸化セリウム（ＣｅＯ２）を有し、触媒成分としてルテニウム（Ｒｕ）を有する、窒素と水素からアンモニアを合成する反応用の触媒の製造方法であって、硝酸セリウム水溶液へＫＯＨ水溶液またはアンモニア水溶液を沈殿剤として添加して得た沈殿を焼成することでＣｅＯ２を調製し、これをＲｕ（ＮＯ）（ＮＯ３）３水溶液に含浸させてＲｕを担持した後、水素処理して、ＣｅＯ２担持Ｒｕ触媒を調製することを特徴とする、触媒の製造方法。
〈２〉上記沈殿の焼成温度が５００－７００℃であることを特徴とする、〈１〉に記載の触媒の製造方法。
〈３〉上記水素処理を３００℃で行うことを特徴とする、〈１〉または〈２〉に記載の触媒の製造方法。
〈４〉窒素と水素からアンモニアを合成する反応用のＣｅＯ２担持Ｒｕ触媒であって、ＣｅＯ２担体のＢＥＴ比表面積が１７～１００ｍ２／ｇの範囲であり、細孔容積が０．０９～０．２５ｍＬ／ｇの範囲であることを特徴とする、触媒。
〈５〉ＣｅＯ２担持Ｒｕ触媒とＭｇＯが混合されてなる、窒素と水素からアンモニアを合成する反応用のＲｕ－ＣｅＯ２とＭｇＯの混合体触媒。
〈６〉混合体におけるＣｅとＭｇのモル比がＭｇ／Ｃｅ＝１～９である、〈５〉に記載の触媒。
〈７〉窒素と水素からアンモニアを合成する反応用のＣｅＯ２担持Ｒｕ触媒であって、ＣｅＯ２担体の表面にモル比Ｒｕ／Ｆｅ＝５～２００の範囲でＦｅが更に担持されていることを特徴とする、触媒。
The present invention has been made based on these findings obtained by the present inventors, and the present application specifically provides the following inventions.
<1> A method for producing a catalyst for the reaction of synthesizing ammonia from nitrogen and hydrogen, which has cerium oxide (CeO 2 ) as a carrier and ruthenium (Ru) as a catalyst component, in which a KOH aqueous solution is added to a cerium nitrate aqueous solution. Alternatively, CeO 2 is prepared by adding an ammonia aqueous solution as a precipitant and calcining the resulting precipitate, impregnating it with an Ru(NO)(NO 3 ) 3 aqueous solution to support Ru, and then hydrogen-treating it. , a method for producing a catalyst, which comprises preparing a CeO 2 -supported Ru catalyst.
<2> The method for producing a catalyst according to <1>, wherein the firing temperature of the precipitate is 500-700°C.
<3> The method for producing a catalyst according to <1> or <2>, wherein the hydrogen treatment is performed at 300°C.
<4> CeO 2 supported Ru catalyst for the reaction of synthesizing ammonia from nitrogen and hydrogen, in which the BET specific surface area of the CeO 2 support is in the range of 17 to 100 m 2 /g and the pore volume is 0.09 to Catalyst, characterized in that it is in the range of 0.25 mL/g.
<5> Ru-CeO 2 and MgO mixture catalyst for the reaction of synthesizing ammonia from nitrogen and hydrogen, which is a mixture of CeO 2 supported Ru catalyst and MgO.
<6> The catalyst according to <5>, wherein the molar ratio of Ce and Mg in the mixture is Mg/Ce = 1 to 9.
<7> A CeO 2 supported Ru catalyst for the reaction of synthesizing ammonia from nitrogen and hydrogen, in which Fe is further supported on the surface of the CeO 2 support at a molar ratio of Ru/Fe = 5 to 200. Features: Catalyst.
アンモニア合成においてＲｕ－ＣｅＯ２触媒は、比較的低温・低圧で作用する触媒であるとともに、条件変化に対して応答性がよいため、変動性である再生可能エネルギーにより製造されたＣＯ２フリー水素を原料にするＣＯ２フリーアンモニア合成プロセスに適した触媒であり、よって、再生可能エネルギーの大量導入にむけた再生可能エネルギー貯蔵の面で社会実装されることが期待される触媒である。
本発明により、より高いアンモニア合成活性を有するＲｕ－ＣｅＯ２触媒を提供することができ、また、ＣｅＯ２の使用量を減らすことで、より安価でＲｕ－ＣｅＯ２触媒を提供することができる。これにより、上記再生可能エネルギーの利用の分野にも資することが期待される。
In ammonia synthesis, the Ru-CeO 2 catalyst works at relatively low temperatures and pressures, and is highly responsive to changes in conditions. This catalyst is suitable for the CO2 - free ammonia synthesis process used as a raw material, and is therefore expected to be socially implemented in the field of renewable energy storage in preparation for the large-scale introduction of renewable energy.
According to the present invention, a Ru--CeO 2 catalyst having higher ammonia synthesis activity can be provided, and by reducing the amount of CeO 2 used, a Ru--CeO 2 catalyst can be provided at a lower cost. This is expected to contribute to the field of renewable energy utilization mentioned above.
以下、本発明を実施例に基づいて更に詳細に説明する。但し、実施例は本発明の例示であって、本発明は実施例に限定されるものではない。 Hereinafter, the present invention will be explained in more detail based on examples. However, the examples are illustrative of the present invention, and the present invention is not limited to the examples.
［実施例１］各種のＣｅＯ２担体を用いたＲｕ－ＣｅＯ２触媒の調製とそのＮＨ３合成活性
（１）以下の要領で、Ｒｕ－ＣｅＯ２触媒の担体として用いる各種のＣｅＯ２を準備した。
（アルカリ水溶液による沈殿法によるもの）
硝酸セリウム重量の約１０倍数の体積のイオン交換蒸留水で硝酸セリウム水溶液を調製し、２７％ＮＨ３水もしくは０．０５－０．１ｍｏｌ／ＬのＫＯＨ、ＮａＯＨを徐々に加えて、ｐＨを１０以上にして得られる沈殿を６００℃で空気中焼成して、ＣｅＯ２を調製した。
（クエン酸水溶液による沈殿法によるもの）
上述の硝酸セリウム水溶液にセリウムの２倍ｍｏｌ量を含むクエン酸水溶液を加え、蒸発乾固させて得た沈殿を６００℃で空気中焼成して、ＣｅＯ２を調製した。
（市販品）
市販されている、比表面積の異なるＣｅＯ２を２種（高表面積および中程度の表面積）、準備した。これらはそれぞれ第一稀元素化学工業製ＣｅＯ２ Ｔｙｐｅ－ＡおよびＴｙｐｅ－Ｂであり、比表面積はそれぞれ１５０ｍ２／ｇおよび１００ｍ２／ｇであった。
（低表面積ＣｅＯ２）
市販のＣｅＯ２ Ｔｙｐｅ－Ａを９００℃、６時間、空気中で焼成して、比表面積９ｍ２／ｇのＣｅＯ２を調製した。
（２）これらのＣｅＯ２に、Ｒｕ（ＮＯ）（ＮＯ３）３水溶液を含浸させて、各種のＲｕ－ＣｅＯ２触媒を調製した。ＣｅＯ２は、メスシリンダーによる見かけの密度および真密度計による真密度を測定し、それらの差分によって得られる見かけの空隙容積を算出した。ＣｅＯ２の重量に応じて、見かけの空隙容積の１．５倍の水に必要量のＲｕ（ＮＯ）（ＮＯ３）３を溶解し、そのＲｕ（ＮＯ）（ＮＯ３）３水溶液中にＣｅＯ２を室温で１時間浸漬した後、１００℃で１２時間乾燥させてＲｕ担持ＣｅＯ２を得た。Ｒｕ担持ＣｅＯ２は、管状炉中で１０％Ｈ２／Ｎ２気流中３００℃、１時間焼成して目的の触媒を調製した。
また、これに加えて、市販の高表面積ＣｅＯ２にＲｕ３（ＣＯ）１２溶液を含浸させて、Ｒｕ－ＣｅＯ２触媒を調製した。上記と同様に測定したＣｅＯ２の見かけの空隙容積の５０倍のテトラヒドロフラン（ＴＨＦ）にＲｕ３（ＣＯ）１２を溶解し、上記と同様の手順で目的の触媒を得た。
得られた各Ｒｕ－ＣｅＯ２触媒のＲｕ担持量は、それぞれ１Ｗｔ％である。
[Example 1] Preparation of Ru-CeO 2 catalyst using various CeO 2 supports and its NH 3 synthesis activity (1) Various CeO 2 to be used as a support for Ru-CeO 2 catalyst were prepared in the following manner. .
(By precipitation method using alkaline aqueous solution)
Prepare a cerium nitrate aqueous solution with ion-exchanged distilled water in a volume approximately 10 times the weight of cerium nitrate, and gradually add 27% NH 3 water or 0.05-0.1 mol/L KOH or NaOH to adjust the pH to 10. The precipitate obtained above was calcined in air at 600° C. to prepare CeO 2 .
(By precipitation method using citric acid aqueous solution)
A citric acid aqueous solution containing twice the molar amount of cerium was added to the above-mentioned cerium nitrate aqueous solution, and the resulting precipitate was evaporated to dryness and calcined in air at 600° C. to prepare CeO 2 .
(Commercial goods)
Two types of commercially available CeO 2 with different specific surface areas (high surface area and medium surface area) were prepared. These were CeO 2 Type-A and Type-B manufactured by Daiichi Kigenso Kagaku Kogyo, respectively, and the specific surface areas were 150 m 2 /g and 100 m 2 /g, respectively.
(Low surface area CeO 2 )
Commercially available CeO 2 Type-A was calcined in air at 900° C. for 6 hours to prepare CeO 2 with a specific surface area of 9 m 2 /g.
(2) Various Ru--CeO 2 catalysts were prepared by impregnating these CeO 2 with an Ru(NO)(NO 3 ) 3 aqueous solution. For CeO 2 , the apparent density using a graduated cylinder and the true density using a true densitometer were measured, and the apparent void volume obtained from the difference between them was calculated. Depending on the weight of CeO2 , dissolve the required amount of Ru(NO)( NO3 ) 3 in water 1.5 times the apparent pore volume, and add CeO to the Ru(NO)( NO3 ) 3 aqueous solution. 2 was immersed at room temperature for 1 hour and then dried at 100° C. for 12 hours to obtain Ru-supported CeO 2 . The Ru-supported CeO 2 was calcined in a tube furnace at 300° C. for 1 hour in a 10% H 2 /N 2 stream to prepare the desired catalyst.
Additionally, a commercially available high surface area CeO 2 was impregnated with a Ru 3 (CO) 12 solution to prepare a Ru-CeO 2 catalyst. Ru 3 (CO) 12 was dissolved in tetrahydrofuran (THF) 50 times the apparent pore volume of CeO 2 measured in the same manner as above, and the target catalyst was obtained in the same manner as above.
The Ru supported amount of each of the obtained Ru--CeO 2 catalysts was 1 wt%.
これらのＲｕ－ＣｅＯ２触媒を用いて、アンモニアの合成試験を行った。試験は常圧固定床流通反応装置を用いて行った。反応温度４００℃で得られたその結果を、図１に示す。
図１に示されるように、硝酸セリウムを水酸化カリウムもしくはアンモニアの水溶液を用いて沈殿・焼成して作製したＣｅＯ２に強酸性のＲｕ（ＮＯ）（ＮＯ３）３（ニトロシル硝酸ルテニウム）の溶液を含浸することにより作製したＲｕ－ＣｅＯ２触媒は、従来のＲｕ３（ＣＯ）１２（Ｒｕカルボニル）を用いて作製した触媒と比べて、高いアンモニア合成活性を有する。これに対し、硝酸セリウムを水酸化ナトリウムやクエン酸により沈殿・焼成して作製したＣｅＯ２を用いた場合のアンモニア合成活性は、従来のＲｕカルボニルを用いて作製した触媒よりも低い。
Ammonia synthesis tests were conducted using these Ru-CeO 2 catalysts. The test was conducted using an atmospheric fixed bed flow reactor. The results obtained at a reaction temperature of 400° C. are shown in FIG.
As shown in Figure 1, a solution of strongly acidic Ru(NO)( NO3 ) 3 (ruthenium nitrosyl nitrate) is added to CeO2 , which is prepared by precipitating and calcining cerium nitrate with an aqueous solution of potassium hydroxide or ammonia. The Ru-CeO 2 catalyst prepared by impregnating Ru 3 (CO) 12 (Ru carbonyl) has higher ammonia synthesis activity than the conventional catalyst prepared using Ru 3 (CO) 12 (Ru carbonyl). On the other hand, the ammonia synthesis activity when using CeO 2 produced by precipitating and calcining cerium nitrate with sodium hydroxide or citric acid is lower than that of a conventional catalyst produced using Ru carbonyl.
また、アンモニア合成活性は、ＣｅＯ２の焼成温度によっても変化し、水酸化カリウムにより沈殿させたＣｅＯ２を用いた上記触媒では、６００℃で焼成したものが最も活性が高かった（図２）。 Furthermore, the ammonia synthesis activity also changes depending on the calcination temperature of CeO 2 , and among the above catalysts using CeO 2 precipitated with potassium hydroxide, the one calcined at 600° C. had the highest activity (FIG. 2).
［実施例２］ＣｅＯ２担体の表面構造と触媒活性の関連性
ＣｅＯ２は塩基性の担体であり、強酸性の溶液で処理するとその表面が一部溶解する。このことが、強酸性のニトロシル硝酸ルテニウムの溶液をＣｅＯ２に含浸することにより作製した本発明の触媒が高いアンモニア合成活性を有することと関連しているのではないかとの想定の下に、ＣｅＯ２を強酸性の溶液で処理したときに生じるＣｅＯ２担体の表面の状態を模するものとして、結晶性のＣｅＯ２に硝酸セリウム水溶液を含浸させ、焼成することで、結晶性ＣｅＯ２の表面に非晶質のＣｅＯ２を、種々のＡｍｏ（非晶質）／Ｃｒｙ（結晶質）の比率で担持した担体を作製し、これにＲｕを担持した触媒を用いてアンモニア合成反応を行った。
[Example 2] Relationship between surface structure of CeO 2 carrier and catalytic activity CeO 2 is a basic carrier, and its surface partially dissolves when treated with a strongly acidic solution. Under the assumption that this may be related to the high ammonia synthesis activity of the catalyst of the present invention prepared by impregnating CeO2 with a solution of strongly acidic ruthenium nitrosyl nitrate, we To imitate the surface state of a CeO 2 carrier that occurs when 2 is treated with a strongly acidic solution, crystalline CeO 2 is impregnated with a cerium nitrate aqueous solution and fired. Supports were prepared in which amorphous CeO 2 was supported at various Amo (amorphous)/Cry (crystalline) ratios, and an ammonia synthesis reaction was carried out using a catalyst in which Ru was supported on the supports.
上記担体および触媒の調製、および、これを用いたアンモニア合成試験は、具体的には、以下のとおりに行った：
実施例１でも用いた市販の高表面積ＣｅＯ２を空気中９００℃で６時間焼成することで、結晶性のＣｅＯ２（以下、ＣｅＯ２（Ｃｒｙ）という）を調製した。
所定量のＣｅＯ２（Ｃｒｙ）を各種濃度のＣｅ（ＮＯ３）３水溶液に含浸し、１００℃で１２時間乾燥させた後、１０％Ｈ２／Ｎ２雰囲気中３００℃で１時間焼成することで、ＣｅＯ２（Ａｍｏ）／ＣｅＯ２（ｃｒｙ）のモル比が、それぞれ０．０１、０．０２、０．１、０．２、０．５、１、２、１０であるＣｅＯ２（Ａｍｏ）／ＣｅＯ２（ｃｒｙ）を調製した。また、硝酸セリウムを３００℃で４時間焼成することで、ＣｅＯ２（Ａｍｏ）のみからなるＣｅＯ２を調製した。これらのＣｅＯ２について測定されたＢＥＴ法による比表面積および細孔容積を図３に示す。黒バーが比表面積を、また白抜き丸が細孔容積を示す。
このようにして調製した各種のＣｅＯ２を、Ｒｕ担持量が１Ｗｔ％となるように濃度調節したＲｕ（ＮＯ）（ＮＯ３）３水溶液中に含浸し、１００℃で８時間乾燥させた後、１０％Ｈ２／Ｎ２雰囲気中３００℃で１時間焼成することで、各種のＲｕ－ＣｅＯ２触媒を調製した。
これらのＲｕ－ＣｅＯ２触媒を用いて、アンモニアの合成試験を行った。アンモニア合成反応の反応条件は、実施例１と同様である。その結果を、図４に示す。
Specifically, the preparation of the above-mentioned carrier and catalyst and the ammonia synthesis test using the same were carried out as follows:
Crystalline CeO 2 (hereinafter referred to as CeO 2 (Cry)) was prepared by baking the commercially available high surface area CeO 2 used in Example 1 at 900° C. for 6 hours in air.
A predetermined amount of CeO 2 (Cry) is impregnated into Ce(NO 3 ) 3 aqueous solution at various concentrations, dried at 100°C for 12 hours, and then fired at 300°C for 1 hour in a 10% H 2 /N 2 atmosphere. and the molar ratio of CeO 2 (Amo)/CeO 2 (cry) is 0.01, 0.02, 0.1, 0.2, 0.5, 1, 2, and 10, respectively. )/CeO 2 (cry) was prepared. Furthermore, CeO 2 consisting only of CeO 2 (Amo) was prepared by baking cerium nitrate at 300° C. for 4 hours. The specific surface area and pore volume measured by the BET method for these CeO2s are shown in FIG. The black bar indicates the specific surface area, and the open circle indicates the pore volume.
Various types of CeO 2 prepared in this way were impregnated in an aqueous solution of Ru(NO)(NO 3 ) 3 whose concentration was adjusted so that the amount of Ru supported was 1 wt%, and after drying at 100 ° C. for 8 hours, Various Ru-CeO 2 catalysts were prepared by calcining at 300° C. for 1 hour in a 10% H 2 /N 2 atmosphere.
Ammonia synthesis tests were conducted using these Ru-CeO 2 catalysts. The reaction conditions for the ammonia synthesis reaction are the same as in Example 1. The results are shown in FIG.
これらの実験の結果、Ａｍｏの比率を高めるにつれて担体の比表面積及び細孔容積は大きくなる（図３）が、触媒のアンモニア合成活性も同様に一律に高まるわけではなく、Ａｍｏ／Ｃｒｙ比が１である場合をピークに、それ以上Ａｍｏの比率を高めるとアンモニア合成活性がかえって低くなる（図４）ことを見出した。図３と４とから、担体の比表面積１７～１００ｍ２／ｇ、細孔容積０．０９～０．２５ｍＬ／ｇの範囲、より好ましくは、２０～６０ｍ２／ｇ、０．０９～０．２ｍＬ／ｇの範囲で高いアンモニア合成活性が得られたことが分かる。
硝酸セリウムを水酸化カリウムもしくはアンモニアの水溶液を用いて沈殿・焼成して作製したＣｅＯ２に強酸性のニトロシル硝酸ルテニウムの溶液を含浸することにより作製したＲｕ－ＣｅＯ２触媒においては、ＣｅＯ２担体の表面が、上述のＡｍｏ／Ｃｒｙ比が１である場合と類似する構造を有しているものと推察される。
As a result of these experiments, the specific surface area and pore volume of the carrier increase as the Amo ratio increases (Figure 3), but the ammonia synthesis activity of the catalyst also does not increase uniformly; It was found that when the Amo ratio was increased beyond the peak value, the ammonia synthesis activity actually decreased (FIG. 4). From FIGS. 3 and 4, it can be seen that the specific surface area of the carrier is in the range of 17 to 100 m 2 /g and the pore volume is in the range of 0.09 to 0.25 mL/g, more preferably 20 to 60 m 2 /g, 0.09 to 0. It can be seen that high ammonia synthesis activity was obtained in the range of 2 mL/g.
In the Ru-CeO 2 catalyst prepared by impregnating CeO 2 prepared by precipitating and calcining cerium nitrate with an aqueous solution of potassium hydroxide or ammonia with a solution of strongly acidic ruthenium nitrosyl nitrate, It is presumed that the surface has a structure similar to that in the case where the Amo/Cry ratio is 1 as described above.
［実施例３］Ｒｕ－ＣｅＯ２触媒へのＭｇＯの混合効果
Ｒｕ－ＣｅＯ２触媒に用いられるＲｕもＣｅＯ２も高価な材料である。本発明者らは、Ｒｕ－ＣｅＯ２触媒におけるＣｅＯ２の一部をＭｇＯで置き換えることで、Ｒｕ－ＣｅＯ２触媒に含まれるＣｅＯ２の量を減らすことを試みた。
[Example 3] Effect of mixing MgO into Ru-CeO2 catalyst Both Ru and CeO2 used in the Ru- CeO2 catalyst are expensive materials. The present inventors attempted to reduce the amount of CeO 2 contained in the Ru-CeO 2 catalyst by replacing part of the CeO 2 in the Ru-CeO 2 catalyst with MgO.
具体的には、以下に示す４種類の触媒を調製し、そのアンモニア合成活性を調べた：
（共沈）
硝酸マグネシウム＋硝酸セリウム重量の約１０倍数の体積のイオン交換蒸留水で硝酸マグネシウムと硝酸セリウムの共水溶液（モル比Ｍｇ／Ｃｅ＝５）を調製し、これに２７％ＮＨ３水溶液を徐々に添加することによりｐＨを１０以上にして得られる沈殿を６００℃、４時間、空気中で焼成し、これにＲｕ（ＮＯ３）３水溶液をＲｕ含有量が１Ｗｔ％となるように含浸担持した後、Ｈ２／Ｎ２雰囲気中３００℃で焼成する。
（物理混合）
ＭｇＯとＣｅＯ２を上述の共沈法と同様の方法でそれぞれ沈殿から調製し、モル比Ｍｇ／Ｃｅ＝５で乳鉢によって混合し、得られたものに、Ｒｕ（ＮＯ３）３水溶液をＲｕ含有量が１Ｗｔ％となるように含浸担持した後、Ｈ２／Ｎ２雰囲気中３００℃で焼成する。
（表面担持）
所定量を秤量した硝酸セリウム水溶液中に上述の沈殿法によって調製したＭｇＯ粉体を浸漬し、蒸発乾固させることで、ＭｇＯ外表面にＣｅを析出させ、続いて、空気中６００℃で４時間焼成し、ＣｅＯ２が表面に担持したＭｇＯ（モル比Ｍｇ／Ｃｅ＝５）を得、これにＲｕ（ＮＯ３）３水溶液をＲｕ含有量が１Ｗｔ％となるように含浸担持した後、Ｈ２／Ｎ２雰囲気中３００℃で焼成する。
（Ｒｕ－ＣｅＯ２＋ＭｇＯ混合）
実施例１においてＮＨ３を用いた沈殿法により得られたＣｅＯ２にＲｕ（ＮＯ３）３水溶液をＲｕ含有量が２．２Ｗｔ％となるように含浸担持し、Ｈ２／Ｎ２雰囲気中３００℃で焼成した後、モル比Ｍｇ／Ｃｅ＝５となるようにＭｇＯをＲｕ－ＣｅＯ２に加えて、乳鉢で混合し、Ｒｕ含有量が混合物全体で１Ｗｔ％となるＲｕ－ＣｅＯ２＋ＭｇＯ混合触媒を得た。
これらの触媒、及び比較対象として、実施例１においてＮＨ３を用いた沈殿法により得られたＣｅＯ２にＲｕ（ＮＯ）（ＮＯ３）３水溶液をＲｕ含有量が１Ｗｔ％となるように含浸担持した後、Ｈ２／Ｎ２雰囲気中３００℃で焼成した触媒について、アンモニアの合成試験を行った。アンモニア合成反応の反応条件は、実施例１と同様である。その結果を、図５に示す。
Specifically, the following four types of catalysts were prepared and their ammonia synthesis activity was investigated:
(co-precipitation)
Prepare a co-aqueous solution of magnesium nitrate and cerium nitrate (molar ratio Mg/Ce = 5) with ion-exchanged distilled water in a volume approximately 10 times the weight of magnesium nitrate + cerium nitrate, and gradually add a 27% NH 3 aqueous solution to this. The precipitate obtained by raising the pH to 10 or higher was calcined in air at 600° C. for 4 hours, and impregnated with Ru(NO 3 ) 3 aqueous solution so that the Ru content was 1 Wt%. Calcinate at 300° C. in H 2 /N 2 atmosphere.
(physical mixture)
MgO and CeO 2 were prepared from precipitates using the same method as the coprecipitation method described above, and mixed in a mortar at a molar ratio of Mg/Ce = 5 . After being impregnated and supported in an amount of 1 wt%, it is fired at 300° C. in an H 2 /N 2 atmosphere.
(Surface supported)
The MgO powder prepared by the above-mentioned precipitation method was immersed in a predetermined amount of cerium nitrate aqueous solution and evaporated to dryness to precipitate Ce on the outer surface of MgO, and then heated in air at 600°C for 4 hours. After baking, MgO with CeO 2 supported on the surface (molar ratio Mg/Ce=5) was obtained, which was impregnated with Ru(NO 3 ) 3 aqueous solution so that the Ru content was 1 Wt%, and then H 2 / N2 atmosphere at 300°C.
(Ru-CeO2+MgO mixture)
CeO 2 obtained by the precipitation method using NH 3 in Example 1 was impregnated and supported with Ru(NO 3 ) 3 aqueous solution so that the Ru content was 2.2 Wt%, and the mixture was heated at 300% by weight in an H 2 /N 2 atmosphere. After firing at ℃, MgO is added to Ru-CeO 2 so that the molar ratio Mg/Ce=5, and mixed in a mortar, resulting in a Ru-CeO 2 +MgO mixed catalyst with a Ru content of 1 Wt% in the entire mixture. I got it.
For these catalysts and for comparison, an aqueous solution of Ru(NO)(NO 3 ) 3 was impregnated and supported on CeO 2 obtained by the precipitation method using NH 3 in Example 1 so that the Ru content was 1 Wt%. After that, an ammonia synthesis test was conducted on the catalyst calcined at 300° C. in an H 2 /N 2 atmosphere. The reaction conditions for the ammonia synthesis reaction are the same as in Example 1. The results are shown in FIG.
図５に示されるように、Ｒｕ－ＣｅＯ２触媒にＭｇＯを混合することで、ＭｇＯの混合量に応じてＲｕ－ＣｅＯ２触媒に含まれるＣｅＯ２の量を減らすことができ、ＣｅＯ２の量を減らさない場合と匹敵するアンモニア合成活性が得られることを見出した。これにより、高価な材料であるＣｅＯ２の、同一のＲｕの量に対する使用量を抑えることができる。
一方、同様の量のＲｕ、ＣｅＯ２およびＭｇＯを用いても、共沈や物理的混合により得られたＣｅＯ２およびＭｇＯの混合物にＲｕを担持した場合や、ＭｇＯ外表面にＣｅＯ２を担持した後、これにＲｕを担持した場合には、このような効果は見られないことから、このような効果を得るためには、ＲｕはＣｅＯ２に集約されて担持されている必要があるものと考えられる。
As shown in Figure 5, by mixing MgO into the Ru-CeO 2 catalyst, the amount of
On the other hand, even if similar amounts of Ru, CeO 2 and MgO are used, Ru is supported on a mixture of CeO 2 and MgO obtained by coprecipitation or physical mixing, or when CeO 2 is supported on the outer surface of MgO. Later, when Ru was supported on this, such an effect was not observed, so in order to obtain such an effect, Ru must be supported in a concentrated manner on CeO2 . Conceivable.
図６に、上述のＲｕ－ＣｅＯ２＋ＭｇＯ混合触媒において、モル比Ｍｇ／Ｃｅが１、３または９の混合触媒を更に調製し、これらと、モル比Ｍｇ／Ｃｅが５の触媒、及び、上述の（物理混合）に記載した調製法で調製したＭｇＯを含まない触媒、並びに、ＣｅＯ２を含まない触媒のアンモニア合成活性を調べた結果を示す。
図６から、上述のＲｕ－ＣｅＯ２触媒にＭｇＯを混合することの効果は、少なくともＭｇ／Ｃｅ比が１～９の範囲で得られ、この範囲で、同じＲｕ担持法による、ＭｇＯを含まない触媒のアンモニア合成活性を上回ることが分かる。
FIG. 6 shows that in the Ru-CeO 2 +MgO mixed catalyst described above, a mixed catalyst with a molar ratio Mg/Ce of 1, 3, or 9 was further prepared, and these, a catalyst with a molar ratio Mg/Ce of 5, and the above-mentioned mixed catalyst were further prepared. The results of investigating the ammonia synthesis activity of a catalyst containing no MgO and a catalyst containing no CeO 2 prepared by the preparation method described in (Physical Mixing) are shown below.
From FIG. 6, the effect of mixing MgO into the Ru-CeO 2 catalyst described above is obtained at least when the Mg/Ce ratio is in the range of 1 to 9. It can be seen that this exceeds the ammonia synthesis activity of the catalyst.
［実施例４］Ｒｕ－ＣｅＯ２触媒へのＦｅ配合の効果
多くの触媒において、第二成分を添加することにより活性が向上する現象が観察されることがある。そこで、本発明者らは、Ｒｕ－ＣｅＯ２触媒において、さらにＦｅを添加することが触媒のアンモニア合成活性に与える影響について検討した。
[Example 4] Effect of adding Fe to Ru-CeO 2 catalyst In many catalysts, it is sometimes observed that the activity is improved by adding a second component. Therefore, the present inventors investigated the effect of further adding Fe to the Ru-CeO 2 catalyst on the ammonia synthesis activity of the catalyst.
具体的には、実施例１で用いた市販の高表面積ＣｅＯ２の見かけの密度および真密度測定から見かけの空隙容積を算出し、その１．５倍体積のイオン交換蒸留水にＦｅ（ＮＯ３）３を溶解した水溶液中にＣｅＯ２を浸漬させ、６００℃、４時間、空気中で焼成し、Ｆｅ／ＣｅＯ２を調製した。これにＲｕ（ＮＯ）（ＮＯ３）３水溶液を用いてＲｕを１Ｗｔ％含浸担持した後、Ｈ２／Ｎ２雰囲気中３００℃で焼成することで、Ｒｕ／Ｆｅ／ＣｅＯ２触媒を得た。Ｒｕ／Ｆｅモル比が０．２～２００の範囲の１０種類の触媒を、Ｆｅ仕込み量を調整しながら調製し、これらの触媒、およびＦｅを担持させない触媒（Ｒｕ／Ｆｅが無限大）ならびにＲｕを担持させない５Ｗｔ％Ｆｅ担持触媒について、アンモニア合成活性を調べた。得られた結果を図７に示す。 Specifically, the apparent pore volume was calculated from the apparent density and true density measurements of the commercially available high surface area CeO 2 used in Example 1, and Fe(NO 3 ) CeO 2 was immersed in an aqueous solution in which Fe/CeO 2 was dissolved and calcined at 600° C. for 4 hours in air to prepare Fe/CeO 2 . This was impregnated with 1 wt% of Ru using a Ru(NO)(NO 3 ) 3 aqueous solution and supported, and then calcined at 300° C. in an H 2 /N 2 atmosphere to obtain a Ru/Fe/CeO 2 catalyst. Ten types of catalysts with Ru/Fe molar ratios in the range of 0.2 to 200 were prepared while adjusting the amount of Fe charged, and these catalysts, catalysts without Fe supported (Ru/Fe is infinite), and Ru The ammonia synthesis activity of the 5 Wt% Fe supported catalyst was investigated. The obtained results are shown in FIG.
図７から、上述の触媒において、モル比Ｒｕ／Ｆｅ＝５～２００の範囲でＦｅを添加することにより、Ｆｅを添加しない場合を上回るアンモニア合成活性が得られることが分かる。特に、モル比Ｒｕ／Ｆｅ＝１００～２００などの極めて少ない量のＦｅの共存によっても上記効果が得られることは、本発明の際立った効果であるといえる。 From FIG. 7, it can be seen that by adding Fe in the molar ratio Ru/Fe=5 to 200 in the above-mentioned catalyst, ammonia synthesis activity higher than that when Fe is not added can be obtained. In particular, it can be said that it is a remarkable effect of the present invention that the above effects can be obtained even with the coexistence of an extremely small amount of Fe such as a molar ratio of Ru/Fe=100 to 200.
アンモニアは、各種化合物の合成反応において原料化合物の１つとして用いられる等、化学工業において広く使用されている化合物であり、本発明は、これらの化学工業の分野で広く利用し得るものである。
また、アンモニアは、再生可能エネルギーの貯蔵の形態の一つとして期待されており、本発明は、この分野での利用も期待される。
Ammonia is a compound widely used in the chemical industry, such as being used as one of the raw material compounds in the synthesis reactions of various compounds, and the present invention can be widely used in these fields of the chemical industry.
Furthermore, ammonia is expected to be a form of renewable energy storage, and the present invention is also expected to be used in this field.
Claims (4)
ＣｅＯ２担体の表面にモル比Ｒｕ／Ｆｅ＝５～２００の範囲でＦｅが更に担持されていることを特徴とする、触媒。 A CeO 2 supported Ru catalyst for the reaction of synthesizing ammonia from nitrogen and hydrogen, comprising:
A catalyst characterized in that Fe is further supported on the surface of a CeO 2 carrier at a molar ratio Ru/Fe=5 to 200.
ＣｅＯ２にＦｅを担持させてＦｅ／ＣｅＯ２を得て、モル比Ｒｕ／Ｆｅ＝５～２００となるように、このＦｅ／ＣｅＯ２にＲｕを担持させる触媒の製造方法。 A method for producing a catalyst for a reaction that synthesizes ammonia from nitrogen and hydrogen, the method comprising:
A method for producing a catalyst in which Fe/CeO 2 is obtained by supporting Fe on CeO 2 and Ru is supported on this Fe/CeO 2 so that the molar ratio Ru/Fe is 5 to 200.
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