Investigation of Dispersion and Localization of Platinum Species in Mazzite Using EXAFS

Abstract

Dispersion and localization of Pt species in mazzite zeolites (0.3% Pt) were studied using an in situ EXAFS technique in the fluorescence mode and transmission electron microscopy. It was shown that an ion exchange with a Pt(NH3)4Cl2 solution followed by calcination led to the formation of small clusters of PtO2 located in the mazzite channels. Small metal particles (NPt-Pt < 4) were found in the zeolite after the reduction of Pt species with hydrogen. The comparison of the results gained with the TEM and EXAFS techniques showed that most of the Pt metal particles were located in the zeolite channels. Treatment of the Pt/mazzite with humid hydrogen at 823 K was found to result in the agglomeration of Pt metal particles up to the diameter of mazzite channels (7.4 Å).