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Direct observation of catalytic oxidation of particulate matter using in situ TEM.

Kamatani K, Higuchi K, Yamamoto Y, Arai S, Tanaka N, Ogura M - Sci Rep (2015)

Bottom Line: Ag/SiO2 catalyzed the reaction at the interface of the mobile Ag species and carbon, while the Cs species was fixed on the nepheline surface during the reaction.In the latter case, carbon particles moved, remained attached to the Cs2CO3/nepheline surface, and were consumed at the interface by the oxidation reaction.Using this technique, we were able to visualize such mobile and immobile catalysis according to different mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Institute of Industrial Science, The University of Tokyo, Komaba 4-6-1, Meguro-ku, Tokyo 153-8505, Japan.

ABSTRACT
The ability to observe chemical reactions at the molecular level convincingly demonstrates the physical and chemical phenomena occurring throughout a reaction mechanism. Videos obtained through in situ transmission electron microscopy (TEM) revealed the oxidation of catalytic soot under practical reaction conditions. Carbon oxidation reactions using Ag/SiO2 or Cs2CO3/nepheline catalysts were performed at 330 °C under an O2 flow of 0.5 Pa in the TEM measurement chamber. Ag/SiO2 catalyzed the reaction at the interface of the mobile Ag species and carbon, while the Cs species was fixed on the nepheline surface during the reaction. In the latter case, carbon particles moved, remained attached to the Cs2CO3/nepheline surface, and were consumed at the interface by the oxidation reaction. Using this technique, we were able to visualize such mobile and immobile catalysis according to different mechanisms.

No MeSH data available.


Related in: MedlinePlus

In situ TEM images of Cs2CO3/nepheline catalyst. (A)–(C) show TEM time course images for carbon oxidation using Cs2CO3/nepheline at 330 °C with an O2 gas flow of 0.5 Pa. (D) shows the TEM image of Cs2CO3/nepheline, and (E) and (F) show EELS mapping on Cs2CO3/nepheline for Cs M-core at RT and 400 °C, respectively. (G)–(I) show TEM time course images during carbon oxidation using only Cs2CO3 at 330 °C with an O2 gas flow of 0.5 Pa.
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f3: In situ TEM images of Cs2CO3/nepheline catalyst. (A)–(C) show TEM time course images for carbon oxidation using Cs2CO3/nepheline at 330 °C with an O2 gas flow of 0.5 Pa. (D) shows the TEM image of Cs2CO3/nepheline, and (E) and (F) show EELS mapping on Cs2CO3/nepheline for Cs M-core at RT and 400 °C, respectively. (G)–(I) show TEM time course images during carbon oxidation using only Cs2CO3 at 330 °C with an O2 gas flow of 0.5 Pa.

Mentions: Figures 3(A) and SI_3 show the TEM image of Cs2CO3/nepheline physically mixed with carbon at 330 °C in vacuum. Images (B) and (C) demonstrate the time course of carbon oxidation at 330 °C, with O2 flowing at 0.5 Pa, acquired over 28 min. In image (A), the dark spheres correspond to Cs2CO3/nepheline, and the gray shadows are the agglomerated carbon particles. As explained above, the nepheline itself did not catalyze carbon oxidation at 330 °C; therefore, the oxidation activity derives from the Cs species. Images (A)–(C) led us to conclude that carbon oxidation occurs at the whole surface of the Cs2CO3/nepheline. This also indicates that the Cs species was highly dispersed on the nepheline surface. During the reaction, carbon particles continuously moved toward the Cs2CO3/nepheline surface, where carbon was oxidized.


Direct observation of catalytic oxidation of particulate matter using in situ TEM.

Kamatani K, Higuchi K, Yamamoto Y, Arai S, Tanaka N, Ogura M - Sci Rep (2015)

In situ TEM images of Cs2CO3/nepheline catalyst. (A)–(C) show TEM time course images for carbon oxidation using Cs2CO3/nepheline at 330 °C with an O2 gas flow of 0.5 Pa. (D) shows the TEM image of Cs2CO3/nepheline, and (E) and (F) show EELS mapping on Cs2CO3/nepheline for Cs M-core at RT and 400 °C, respectively. (G)–(I) show TEM time course images during carbon oxidation using only Cs2CO3 at 330 °C with an O2 gas flow of 0.5 Pa.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495604&req=5

f3: In situ TEM images of Cs2CO3/nepheline catalyst. (A)–(C) show TEM time course images for carbon oxidation using Cs2CO3/nepheline at 330 °C with an O2 gas flow of 0.5 Pa. (D) shows the TEM image of Cs2CO3/nepheline, and (E) and (F) show EELS mapping on Cs2CO3/nepheline for Cs M-core at RT and 400 °C, respectively. (G)–(I) show TEM time course images during carbon oxidation using only Cs2CO3 at 330 °C with an O2 gas flow of 0.5 Pa.
Mentions: Figures 3(A) and SI_3 show the TEM image of Cs2CO3/nepheline physically mixed with carbon at 330 °C in vacuum. Images (B) and (C) demonstrate the time course of carbon oxidation at 330 °C, with O2 flowing at 0.5 Pa, acquired over 28 min. In image (A), the dark spheres correspond to Cs2CO3/nepheline, and the gray shadows are the agglomerated carbon particles. As explained above, the nepheline itself did not catalyze carbon oxidation at 330 °C; therefore, the oxidation activity derives from the Cs species. Images (A)–(C) led us to conclude that carbon oxidation occurs at the whole surface of the Cs2CO3/nepheline. This also indicates that the Cs species was highly dispersed on the nepheline surface. During the reaction, carbon particles continuously moved toward the Cs2CO3/nepheline surface, where carbon was oxidized.

Bottom Line: Ag/SiO2 catalyzed the reaction at the interface of the mobile Ag species and carbon, while the Cs species was fixed on the nepheline surface during the reaction.In the latter case, carbon particles moved, remained attached to the Cs2CO3/nepheline surface, and were consumed at the interface by the oxidation reaction.Using this technique, we were able to visualize such mobile and immobile catalysis according to different mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Institute of Industrial Science, The University of Tokyo, Komaba 4-6-1, Meguro-ku, Tokyo 153-8505, Japan.

ABSTRACT
The ability to observe chemical reactions at the molecular level convincingly demonstrates the physical and chemical phenomena occurring throughout a reaction mechanism. Videos obtained through in situ transmission electron microscopy (TEM) revealed the oxidation of catalytic soot under practical reaction conditions. Carbon oxidation reactions using Ag/SiO2 or Cs2CO3/nepheline catalysts were performed at 330 °C under an O2 flow of 0.5 Pa in the TEM measurement chamber. Ag/SiO2 catalyzed the reaction at the interface of the mobile Ag species and carbon, while the Cs species was fixed on the nepheline surface during the reaction. In the latter case, carbon particles moved, remained attached to the Cs2CO3/nepheline surface, and were consumed at the interface by the oxidation reaction. Using this technique, we were able to visualize such mobile and immobile catalysis according to different mechanisms.

No MeSH data available.


Related in: MedlinePlus