Catalytic properties, size and location of cobalt clusters prepared by the reduction of cobalt ion-exchanged NaY

Abstract

Characterization of cobalt metal clusters supported on NaY zeolite has been carried out by means of ferromagnetic resonance (FMR) spectroscopy, H₂ consumption and probe reactions such as hydrogenation of carbon monoxide and hydrogenolysis of ethane. In order to study the effects of the location, shape and size of the cobalt metal clusters, various catalysts were prepared by ion-exchange, impregnation and other special methods. The reducibility, FMR spectra and catalytic properties of prepared cobalt clusters varied with the methods of preparation and pretreatment conditions, indicating that we could control the location and size of cobalt clusters by changing the preparation conditions. The diameters of prepared cobalt metal clusters varied from <1 nm to 100 nm. Their locations varied from the sodalite cage and supercage to the exterior surface of the zeolite resulting in significant changes in the shape and intensity of the FMR band and in the catalytic properties.