Identification of isolated Pt atoms in H-mordenite

Abstract

The state and dispersion of Pt supported on mordenite have been studied using FTIR spectroscopy, CO Chemisorption, and H–D isotope exchange of cyclopentane. Under conditions for which other criteria indicate the presence of monatomic Pt⁰, a characteristic IR band of adsorbed CO is identified at 2123 cm^–1. The position of this band does not change with CO coverage, indicating an interaction between CO and highly dispersed Pt. A significant blue shift of the band with respect to that of CO on multiatomic Pt clusters and the disappearance of this band upon neutralizing the acidic OH groups show that the Pt atoms are electron-deficient and interact with zeolite protons. These FTIR data thus confirm the presence of extremely small Pt clusters, presumably [Pt₁—H_z]^z+ adducts, in H-mordenite.