Time-resolved XAS and XRD studies on the solid-state ion exchange of platinum into zeolite Y

The course of solid-state ion exchange of NH 4 Y zeolite with platinum oxide, chloride and bromide was monitored by TPR, XRD and ― for the first time ― by DEXAFS. In the absence of air PtO 2 and PtCl 2 are reduced at about 300° C to oxidation state zero by ammonia from the zeolite under formation of highly dispersed platinum clusters. In the presence of air this reduction is inhibited and the chlorine neighbour of Pt is replaced by oxygen. Hydrogen treatment resulted in a reduction to a formal oxidation number lower than zero which might be tentatively explained either by formation of a hydride phase or by quantum-size effects