Modification of zeolites by multi-charged cations by the use of in-situ formed “active gas-phase species”

Abstract

A new way of the modification of zeolites is discussed which is based on the use of active gas-phase species formed in situ upon thermal treatment of a [H-zeolite+modifier oxide] mixture with an air flow containing CCl 4 . The chemical transport reaction, with the formation of reactive and mobile oxychloride fragments in the zeolitic bed, provides effective dissipation of the oxide phase and migration of active species into the zeolitic channels at temperatures as low as 150–300°C. ESR is used as an informative and sensitive method to monitor transformations in systems containing paramagnetic ions. The peculiarities of the introduction of Mo 5+ ions into the H-forms of several zeolites (ZSM-5, beta, ferrierite, USY) differing in channel size and structure are discussed. Some transformations of H-ZSM-5 containing Fe 3+ and Gd 3+ ions are also studied.