Pt/SiO2 catalyst preparation: high platinum dispersions by using low temperature treatments.

A method to prepare platinum on silica catalyst using temperatures as low as possible is a goal of this study. Therefore, thermal stability in both oxidizing and reducing atmosphere of 8 different precursors was studied with thermogravimetric analyses (TGA). Based on these data, the precursors were tested to prepare silica supported catalysts, resulting in relationship between the thermal stability of the precursors, the procedures of impregnation, reduction and calcination with the final dispersion on silica. Platinum precursors decomposed more easily in reducing than in oxidizing environment, due to thermochemistry. Catalysts prepared by using ion-exchange and direct reduction in hydrogen resulted in highly dispersed platinum particles on silica. PtClx and PtOx species, when present during catalyst preparation, cause platinum sintering at temperatures higher than 250°C (PtClx) and 350°C (PtOx), respectively. These species can be converted more easily in hydrogen than in air