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Issue 14, 2005
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In situXANES study of Mn in promoted sulfated zirconia catalysts

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Abstract

Mn-promoted sulfated zirconia catalysts (2 wt% Mn) were investigated in situ, during the catalyst activation, isomerization of n-butane, and subsequent re-activation, using X-ray absorption spectroscopy of the Mn K-edge. The average valence of Mn in the catalysts, as determined from the edge position, was found to change from either 2.65 or 2.77 in the calcined samples to about 2.5 during activation in He (703 K for 30 min). During the isomerization of n-butane (1% in He, 80 ml min−1, 0.5 g catalyst at 333 K), the average Mn valence did not change further. When the catalyst was activated in 50% O2 the average valence only decreased from about 2.78 to 2.72. In this case, the average valence during the isomerization reaction decreased at a nearly constant rate both during the induction of activity and deactivation of the catalyst. The data do not support a stoichiometric redox reaction involving the promoter as initiator of the isomerization. However, a higher Mn valence after activation was indicative of a higher maximum conversion. It is concluded that the promoter cations function through modification of the structure of the zirconia.

Graphical abstract: In situ XANES study of Mn in promoted sulfated zirconia catalysts

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Article information


Submitted
19 Apr 2005
Accepted
31 May 2005
First published
17 Jun 2005

Phys. Chem. Chem. Phys., 2005,7, 2830-2838
Article type
Paper

In situ XANES study of Mn in promoted sulfated zirconia catalysts

R. E. Jentoft, A. H. P. Hahn, F. C. Jentoft and T. Ressler, Phys. Chem. Chem. Phys., 2005, 7, 2830
DOI: 10.1039/B505464H

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