X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) Spectra of Pt—Sn—Alumina Catalysts

This report concerns one of four groups of Pt/Sn loaded catalysts, prepared according to selected protocols, which incorporated a range of Sn loadings (0.4 to 3.4%), with Pt maintained at 1%. The X-ray fluorescence and absorption spectra of these preparations were recorded, for both the calcined and reduced states, at the CHESS facility. The near-edge and extended-edge spectra, at the Pt L III and Sn K-edges, were analyzed to ascertain the states of the metallic constituents. Spectra of the pure metals, of alloys (Pt/Sn 1:1 and 3:1), of their oxides and chlorides were used for calibration. Both the near and extended edge spectra show that reduction with H2 at 773K (one atm) for 5 hours leaves major fractions of oxides and chlorides unreduced, but enhances dispersion. Differences due to tin loading are discernible. A radial distribution peak may be assigned to (Sn-Pt) scattering, but by itself is not sufficient to demonstrate the development of alloy clusters upon reduction.