State of tin in Pt-Sn/Al2O3 reforming catalysts investigated by TPR and chemisorption

The state of tin in Pt-SnAl2O3 was investigated by temperature-programmed reduction (TPR) and adsorption of H2 and of O2. With both these independent methods a partial reduction of SnIV to Sn0 was detected. This Sn0 is alloyed with Pt. The composition of the alloy only depends on the total tin content. The main part of SnIV is reduced only to SnII. The reduction of all the SnIV is catalyzed by Pt. At higher temperatures (500 °C) Pt and/or Sn species were found to become mobile. A model of the surface topography is proposed.