PLATINUM SPECIATION DURING SUPPORTED CATA LYSTS PREPARATION FOLLOWED BY PT-195 NMR

Platinum speciation during supported catalysts preparation followed by Pt-195 NMR. The initial steps of Pt/Al2O3 and Pt/SiO2 preparation fro m hexachloroplatinate solutions were studied by both liquid-state and solid-state Pt-195 NMR spectroscopy. These two techniques can provide new information at three levels: (i) liquid-state Pt-195 NMR spectrosc opy evidences changes in platinum speciation in solution upon contact with the solid support; (ii) Pt-195 NMR allows direct observation of a dsorbed species at the support/solution interface and the study of the ir interaction with the support; and (iii) solid-state Pt-195 NMR spec troscopy allows further reactions of the platinum species on drying an d low-temperature thermal treatments to be followed, as long as the lo cal symmetry remains quasi-octahedral. The information gained in this way also leads to significant progress in the interpretation of other experimental results, for example, the temperature-programmed reductio n of Pt/SiO2.