Dispersion and states of platinum ions in BEA-zeollite pores: effect of the framework basicity

摘要

Pt/Cs-BEA materials prepared by a classical ion-exchange procedure using two Cs-BEA supports with different Cs loadings, and a reference acidic Pt/H-BEA, have been studied to investigate the effect of the framework basicity (evaluated by FT-IR of adsorbed CO2) on the state of platinum species after the initial steps (introduction of Pt complex by ion-exchange and subsequent calcination) of the preparation procedure. DR-UV data revealed that the framework basicity affects the structure of the Pt2+ complexes introduced as countercations in the zeolite by ion exchange. FT-IR spectra of adsorbed CO indicated that zeolite basicity rules the fate of platinum species in the subsequent calcination. Hence, in Pt/H-BEA essentially well dispersed Pt delta+ (4 >= delta >= 1) are present, while PtOx particles progressively prevail as the basic character of the zeolite increases.