Synthesis of Pt pillared clay nanocomposite catalysts from [PtII(NH3)(4)]Cl-2 precursor

Pt-containing nanocomposite catalysts were synthesized by deposition of [Pt(NH3)(4)](2+) complex ions on several samples of Al pillared clays, differing in the nature of the parent clay and in the pillaring procedure. In particular, we compared classical Keggin-Al-13 pillared clays, with a rather open microporous network, with the new Al-13-heidi pillared clays, containing bulkier polycations. In Keggin-Al-13 pillared clays, Pt deposition occurred by grafting of the precursor complex ions on specific sites of the pillars. Upon subsequent H-2 reduction, mobile Pt species were formed that grew into large raft-like Pt-0 particles located between the clay layers, causing substantial disruption of the microporous network. In Al-13-heidi pillared clays, on the other hand, diffusion of the [Pt(NH3)(4)](2+) was strongly hindered, and Pt-0 particles were probably formed chiefly outside the clay layers. These structural differences translated into different activities for the reaction of benzene hydrogenation: Pt catalysts supported on Keggin-Al-13 pillared clays were much more active than a reference Pt/Al2O3 or than Pt/Al-13-heidi pillared clays, probably due to the existence of specific bifunctional sites at the interface between interlayer Pt-0 particles and acidic Al-containing pillars.