Surface coordinate geometry of iron catalysts: Distinctive behaviors of Fe/Al{sub 2}O{sub 3} in CO hydrogenation

Journal Article · Thu Feb 08 04:00:00 EST 1996 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp952577m· OSTI ID:219693

Kou, Y; Wang, H L; Niu, J Z; Ji, W J ^[1]

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1. Lanzhou Inst. of Chemical Physics (China)

Two well-defined iron catalysts, Fe(II)/Al{sub 2}O{sub 3} (4.5 wt %) and Fe{sub 2}O{sub 3}/Al{sub 2}O{sub 3} (1.5 wt %), have been studied using Fe K-edge X-ray absorption fine structure (XAFS). The total coordination number of the nearest oxygen neighbors is found to be 4.9 for the former and 5.7 for the latter, but the average Fe-O bond length remains the same, 1.98 A. The nearest iron neighbors at 2.95-2.97 A are observed for both the catalysts, but for the Fe{sub 2}O{sub 3}/Al{sub 2}O{sub 3}, further two iron neighbors at 3.42 and 3.86 A are also present. The fact that the shell radius of 3.42 A is 2/3{radical}3 times longer than that of the first nearest irons is consistent with what is expected from the para- and meta-positions surrounding the same oxygen on the {gamma}-Al{sub 2}O{sub 3} (111) plane but is at variance with the estimation made for the (110) plane. Two geometrical models proposed for the catalysts stoichiometrically explain why the higher metal loading only leads to one type of the iron neighbors but the lower metal loading unexpectedly leads to three types of iron neighbors. 19 refs., 6 figs., 2 tabs.

• OSTI ID: 219693
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 6 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ABSORPTION SPECTRA
ALUMINIUM OXIDES
BOND LENGTHS
CARBON MONOXIDE
CATALYSTS
COORDINATION NUMBER
GEOMETRY
HYDROGENATION
IRON
IRON OXIDES
MOLECULAR STRUCTURE
X-RAY SPECTRA