Distribution of the cobalt-containing component in the pore space of HZSM-5 upon a postsynthetic modification of the zeolite with hydroxo compounds of Co2+

Abstract

The distribution of the cobalt-containing modifying component in the pore space of zeolite HZSM-5 depending on the total cobalt content of the samples (0.5-5.0 wt %) was quantitatively studied for the first time. At cobalt concentrations to 3.0 wt %, the cobalt-containing modifying component mainly occurred as isolated CoOh2+ ions in the micropores (channels) of HZSM-5 at the ion-exchange positions of the zeolite and in one-dimensional CoO and CoAl2O4 nanoclusters. A further increase in the cobalt concentration to 5.0 wt % resulted, in addition to the filling of micropores, in the partial filling of the mesopore space of the zeolite with a small amount of three-dimensional CoO and CoAl2O 4 nanoparticles. Using sorption data and electronic diffuse reflectance spectra, we were the first to find that the effective density of a cobalt-containing modifying component in the pore space of a zeolite matrix was lower than the density of a bulk CoO phase by a factor of 6. © 2008 MAIK Nauka.