PLATINUM-TIN ALUMINA CATALYST - MODIFICATION OF THE METALLIC PHASE AFTER SUCCESSIVE OXIDATION-REDUCTION CYCLES

Pt-Sn/Al2O3 catalysts, prepared by different deposition techniques and submitted to successive oxidation-reduction cycles at 500°C, were characterized by TPR and test reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis), and compared with fresh samples. Interpretation of the results is based on the fact that in catalysts obtained by both coimpregnation and successive impregnation, a higher quantity of Pt-Sn alloys was produced as a consequence of the oxidation-reduction cycles. In catalysts prepared by impregnating the support with the [PtCl2(SnCl3)2]2- complex, the cycles produced changes in the metallic phase probably due to either a surface enrichment of tin in alloy particles or a modification of the alloy phase composition.