Template synthesis of 3D-structured macroporous oxides and hierarchical zeolites

Abstract

The synthesis of macroporous supports using nanosized templates, which are then removed from the final product by burning or dissolution, has been extensively developed since 1997. Here, we report the template synthesis of 3D-structured macroporous supports of different chemical natures, namely, alumina, titanium and zirconium dioxides, and hierarchical silicalite and Fe-silicalite with the zeolite ZSM-5 structure. The templates consist of monodisperse, close-packed, polystyrene spheres 250 to 1150 nm in diameter. The template synthesis affords a marked increase in the specific pore volume and in the external surface area of the porous oxides. The pore volume of granular alumina samples obtained in the absence and in the presence of the polystyrene template is 0.34 and 1.22 cm 3 /g, respectively. The specific external surface area of Fesilicalite with the ZSM-5 structure increases from 26.8 to 410 m 2 /g on passing from the sample synthesized without a template to the sample prepared in the presence of the polystyrene template. The textural properties of the new materials are very promising for adsorption and catalytic processes involving macromolecular compounds, such as catalytic refining of heavy petroleum fractions and biomass and lignin conversion into chemical products, including liquid hydrocarbons; for the pharmaceutical industry; and for adsorption of large molecules, including heavy metals, from aqueous solutions.