THE INFLUENCE OF PLATINUM AMMINE COMPLEX IONIC VALENCE ON PT-SUPPORTED SIO2 BY ION-EXCHANGE

Platinum was supported on silica gel from tetraammineplatinum (II) dic hloride and hydroxyopentaammineplatinum (IV) trichloride, hereafter re ferred to simply as Pt (II) ammine and Pt (IV) ammine, and their adsor ption behavior and the platinum surface area were compared. Various pH s adjusted by ammonia were applied for ion exchange adsorption of the platinum complex ions onto silica gel. The maximum value of Pt (IV) am mine adsorption appeared as a relation of pH though the adsorption of Pt (II) ammine was increased with increasing pH. The direct hydrogen r eduction of the adsorbed complex ions into Pt metal gave a higher plat inum surface area as compared with calcination pretreatment in air. Th e platinum surface area from Pt (IV) ammine was decreased with increas ing pH over 7.2 though the surface area from Pt (II) ammine was indepe ndent of pH. Pt (IV) ammine adsorption in the range of pH < 7.2 gave a higher platinum surface area than Pt (II) ammine.