The genesis of carbon-supported Fe-Mn and K-Fe-Mn catalysts from stoichiometric mixed-metal carbonyl clusters. II. Characterization by Moessbauer spectroscopy and TEM/EDS

Journal Article · Tue Aug 01 04:00:00 EDT 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90331-X· OSTI ID:7271273

Chen, A A; Phillips, J; Venter, J J; Vannice, M A ^[1]

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1. Pennsylvania State Univ., University Park, PA (USA)

Moessbauer effect spectroscopy (MES) and transmission electron microscopy/energy-dispersive X-ray spectroscopy (TEM/EDS) were used to study the chemistry of the iron particles produced by the thermal decomposition of stoichiometric K-Fe, Fe-Mn, and K-Fe-Mn mixed-metal carbonyl clusters on a high surface area carbon. Intermediate chemical states during the cluster decomposition process below 473 K were identified using MES, and they indicated that decarbonylation occurred via the formation of Fe(CO){sub 5} and (Fe{sub 4}(CO){sub 13}){sup {minus}} during heating in H{sub 2}. Following decomposition at 473 K, the principal final phase was the D-structure, which has been associated with superparamagnetic Fe combined with an Fe{sup 2+} state. Additionally, a doublet characteristic of Fe{sup 3+} oxide and/or superparamagnetic carbide appeared in the spectrum. No evidence for a mixed spinel such as Fe{sub 2}MnO{sub 4} was obtained, but the Fe and Mn appeared to remain in contact, presumably as MnO{sub x} on top of small Fe crystallites. A subsequent treatment in H{sub 2} at 673 K caused the K-promoted catalyst to sinter and form separate phases of Mn oxide and large particles of {alpha}-Fe, as detected by MES and TEM/EDS. For the unpromoted Fe-Mn sample, little sintering occurred under H{sub 2} at 673 K, and the particles existed in a phase which has been previously found in Fe-only carbon-supported catalysts.

• OSTI ID: 7271273
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 118:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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