Silicalite-1 hollow spheres and bodies with a regular system of macrocavities

Silicalite-1 macrostructures in the form of hollow silicalite-1 spheres and bodies with a regular system of macrocavities were prepared using two types of polystyrene beads as shape-directing macrotemplates. The incompatibility between the organic support and the inorganic shell was circumscribed by using negatively charged substrates, reverse of their surface charge, and adsorption of zeolite nanoseeds. These pretreated microbeads were subsequently subjected to a continuous growth in a zeolite precursor mixture. The combustion of the polystyrene core leads to the transformation of the core/shell beads into hollow silicalite-1 spheres. The mechanical properties of the latter were found to be a function of the thickness of the silicalite-1 shell, the diameter-to-wall thickness (d:t) ratio, and the calcination conditions. Silicalite-1 bodies with a regular system of macrocavities were prepared by hydrothermal treatment with a silicalite-1 precursor mixture of a layer of pretreated polystyrene beads deposited in a confined space. The obtained body comprised the polystyrene macrotemplates, which after combustion left a regular system of macrocavities. The formation of silicalite-1 macrostructures and their specific properties was studied by XRD, SEM, and TG/DTA analyses and N-2 adsorption measurements.