Synthesis of Pt pillared clay nanocomposite catalysts from [PtII(NH3)4]Cl2 precursor

Abstract

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-Al13 pillared clays, with a rather open microporous network, with the new “Al13-heidi” pillared clays, containing bulkier polycations. In Keggin-Al13 pillared clays, Pt deposition occurred by grafting of the precursor complex ions on specific sites of the pillars. Upon subsequent H2 reduction, mobile Pt species were formed that grew into large raft-like Pt0 particles located between the clay layers, causing substantial disruption of the microporous network. In Al13-heidi pillared clays, on the other hand, diffusion of the [Pt(NH3)4]2+ was strongly hindered, and Pt0 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-Al13 pillared clays were much more active than a reference Pt/Al2O3 or than Pt/Al13-heidi pillared clays, probably due to the existence of specific bifunctional sites at the interface between interlayer Pt0 particles and Bronsted acidic Al-containing pillars.