National Institute Of Materials Physics - Romania

Silicalite embedded BiOx Clusters were prepared both with and without Na using sodium silicate and tetraethylorthosilicate as silicium precursors. Catalysts with 3 and 5 wt% Bi were obtained. The MFl structure was established from XRD, TEM, and N-2 adsorption measurements. No deterioration of the silicalite framework by bismuth was observed. Bi exists as BiOx clusters as evidenced from XPS and EXAFS characterization. These clusters are localized inside the silicalite channels. Py-FTIR measurements indicated that 5wt% Bi led to the formation of strong Lewis acid sites. Epoxidation of cyclohexene was found to depend oil both Bi and Na content. On 3%Bi-ZSM-5 it occurred with rather good conversion and selectivity to epoxide. No visible leaching was evidenced. The catalysts were reused for several runs.