Hydrothermal synthesis and crystallization of zeolites

Abstract

Silicalite-1 layers were successfully grown by standard hydrothermal syntheses on macroporous carbon discs and tested as membranes. All the carbon supports were previously oxidized to favor the anchoring of the zeolite-like material. The silicalite-1 crystals were synthesized using different templates, pHs, ageing times, and hydrothermal synthesis times and temperatures. Some synthetic routes proved to be more useful and reproducible for growing continuous and defect-free layers of silicalite-1 on the surface of a carbon disc. The control of the ageing time, oxidation of the support, use of clear solutions, and the pH of the synthesis solution are key parameters for a successful synthesis, as previously reported. Permeation studies of the prepared composites after removal of the template with both pure gases and gas mixtures proved that the prepared materials show good membrane properties.