XPS STUDY ON THE EFFECTS OF TREATMENTS ON PT2+ AND CO2+ EXCHANGED INTO NAY ZEOLITE

X-ray photoelectron spectroscopy was applied to investigate Pt/NaY, Co /NaY and Pt-Co/NaY zeolites prepared by ion exchange (IE) and impregna tion (IM). Changes in the electronic states and surface distribution o f sodium and silicon were followed in NaY and in Pt and Co containing NaY in the as prepared (AP), calcined (OX) and reduced (RE) states. De coration of the zeolite surface by alumina detected, is attributed to the local processes during ion exchange. Introduction of Co2+ ions int o the Pt-containing samples influences the electronic states of platin um both in calcined and reduced state. Pt-degrees facilitates reductio n of Co2+ ions and formation of bimetallic Pt-Co particles within the zeolite supercages could also be evidenced. The results support earlie r TPR measurements indicating the presence of very small Pt-Co bimetal lic particles for (IE) samples. On the other hand, in the impregnated NaY no sodium exchange occurs and the transition-metal species are loc ated at the external surface of NaY zeolites.