IN-SITU X-RAY-ABSORPTION SPECTROSCOPIC STUDY OF A HIGHLY DISPERSED PTSN/AL2O3 CATALYST

The state of platinum in a PtSn/Al2O3 catalyst prepared from organometallic precursors was studied in situ by EXAFS and XANES spectroscopies. While the XANES spectra show that the platinum is completely reduced after treatment in H-2 at 773 K, the results obtained by EXAFS indicate that, besides platinum and tin, oxygen atoms are present in the first coordination shell of platinum, but with a Pt-O distance longer than for platinum oxide (2.24 vs 2.02 angstrom). These findings can be rationalized assuming the formation of a highly dispersed bimetallic platinum-tin phase, which is stabilized on the alumina surface through Pt-O-Sn2+ bonds.