Synthesis of platinum-tin/alumina reforming catalysts from a well-defined platinum-tin precursor complex

The complex [(CH3)(4)N](3)[Pt(SnCl3)(5)] was selected as a molecular precur sor to prepare PtSn/gamma (c)-Al2O3 reforming catalysts. The spectroscopic fingerprints of the starting complex were obtained by Pt-195 and Sn-119 NMR and diffuse reflectance UV-visible spectroscopy. A series of supported cat alysts were synthesized by wet impregnation of alumina with a solution of t he precursor in acetone. Well-dispersed species are obtained for Pt loadings below 1 wt.%; at higher loadings, a second species is formed that has spectroscopic features remin iscent of the initial complex and precipitates as a separate phase. Apparen tly, the Pt-Sn bonds are hydrolyzed in the low-loading species and preserve d in the high-loading species. The thermal transformations of PtSn/gamma (c)-Al2O3 catalysts are also stud ied and compared with those of the bulk precursor. In particular, it is sho wn that the nature of the atmosphere of thermal treatment (neutral or oxidi zing) can orient the final catalyst towards preservation of an intimate Pt- Sn interaction, or towards demixtion. (C) 2001 Elsevier Science B.V. All ri ghts reserved.