Manganese, iron and sulfur K edge XAFS of promoted sulfated zirconia catalysts

Promoted sulfated zirconia samples were prepared by the incipient wetness t echnique to produce isomerization catalysts which were active for the conve rsion of n-butane to isobutane at 338K (up to 10% conversion of 1% n-butane , 1atm., 0.25 h(-1) WHSV). The local structure of Fe and Mn in promoted sul fated zirconia was investigated using fluorescence yield XAS. Spectra were taken of calcined samples, activated samples, and samples after reaction wi th n-butane (maximum activity and deactivated). Factor analysis reveals tha t the Mn K edge XANES can be described by a linear combination of the spect ra of two separate components, and that the ratio of these components chang es with activation of the catalyst, and during use in the n-butane isomeriz ation reaction. The change in ratio of the Mn species during activation and reaction results in a reduction of the average Mn valence from 2.4 to 2.2. The Fe K edge XANES was not similarly affected by activation and reaction with n-butane.