PT-SN/AL2P3 CATALYSTS PREPARED WITH NOVEL BIMETALLIC PRECURSORS - CHARACTERIZATION AND CATALYTIC ACTIVITY

New bimetallic compounds are proposed as models for the preparation of Pt-Sn/Al2O3 reforming catalysts. [Pt(NH3)(4)][SnCl4], [Pt(NH3)(4)][SnCl6] and [Pt(NH3)(4)][PtCl2(SnCl3)(2)] have been recently synthesized and characterized by XRD, EXAFS and infrared spectroscopy, The air calcination of the precursors leads to the formation of platinum clusters and the loss of tin whereas the H-2 reduction gives only the PtSn alloy. The supported samples prepared by formation of the bimetallic precursors in the porosity of the carrier show a better (Pt-Sn) interaction than conventional catalysts obtained by coimpregnation or successive impregnations. This interaction displays low catalytic activity for cyclohexane dehydrogenation and depends on the activation conditions or aging of the catalysts.