Effect of the Zeolitic Matrix on the Reduction Process of Cu2+ Cations in Clinoptilolite, Mordenite and Erionite

Abstract

Three different zeolites (erionite, mordenite and natural clinoptilolite) were used to study influence of zeolite topology on the state of copper during ion-exchange and following reduction in hydrogen flow. This comparative study clearly demonstrates the influence of used zeolite matrices on the process of implantation of copper nanospecies. Starting from the ion-exchange, the alterations in the state of Cu2+ ions start to be evident due to variations of the intensity of charge transfer band. Copper ions start to reduce at specific temperatures depending on the type of zeolite matrix. Copper plasma resonance band change its shape and position for different zeolites. In the case of Cu-CLI samples this band change both the shape and position for different temperature of reduction. These observations permit to suggest that the mechanism of copper ion reduction and agglomeration to form copper nanoparticles noticeably depend on the type of zeolite matrix. This mechanism is more complex for the Cu CLI than for the Cu-MOR and Cu-ERI systems. Copper nanoparticles formed at low temperatures in the case of Cu-CLI samples undergo changes while temperature of reduction grow.