ISSN:
1572-879X
Keywords:
sulfated zirconia
;
Fe–Mn‐promoted catalysts
;
n‐butane isomerization
;
Mössbauer spectroscopy
;
X‐ray photoelectron spectroscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Iron‐promoted sulfated zirconia catalysts have been characterized by Mössbauer spectroscopy and XPS before and after catalytic test for the isomerization of n‐butane. The data obtained by Mössbauer spectroscopy show that iron is present in the fresh catalysts at the surface of zirconia both as isolated cations and small ferric oxide particles. The diameters of these particles do not exceed 4 nm. The characterization of the catalysts by Mössbauer spectroscopy after 20 and 120 min of reaction shows no apparent reduction of the iron cations. However, the analysis of the peak of Fe 3d3/2 in the XPS spectra shows that iron has been partially reduced in the used catalysts. These apparently contradictory results could be explained by the study of a pre‐reduced catalyst by both techniques. This study shows first that the Fe3+ cations in the particles can be reduced into Fe2+ and reoxidized at room temperature, and second that the reduction observed by XPS corresponds to the departure of the O2 re‐adsorbed at room temperature under air, occurring when the catalysts are placed under vacuum. All the data obtained seemed to confirm that the loss of the promoting effect of iron during the catalytic reaction may partially be due to the irreversible reduction of the iron species susceptible to undergo such reduction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1019003523926
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