Preparation of Zeolite from Ordered Mesostructured Carbon-Silica Nanocomposites
The development of the M41S family triggered the synthesis of wide variety of ordered mesoporous silicas with diverse symmetries using various templating agents such as the quaternary ammonium cationic surfactants and nonionic triblock copolymers. Mesoporous silicas contain ordered uniform pore systems similar to microporous zeolites, but mesostructures are not crystalline. The framework of the silicas are made up of amorphous silica. Thus, owing to their poor hydrothermal stability and weak acidity caused by the amorphous nature of the mesopore walls, practical utilization seems to be limited. It is thus very attractive to synthesize a material, which has the advantages of both zeolites and mesoporous materials.
In this study, we studied that the creation of zeolite inside meso-framework through a solid rearrangement process using hydrothermal synthesis using structure-directing agents or vapor phase transport (VPT) methods. Our strategy is as follows: first, ordered mesoporous carbon-silica composites are prepared. Carbon-silica composites have ordered mesopores and framework of carbon-silica. The composites obtained are crystallized whereas the part of carbon act as a template to retain the ordered mesostructure.
The nucleation and crystal growth of the zeolite occurred on the surface of the carbon-silica composites, although the part of carbon framework is essential to preserve the mesopores. The fabricated materials were zeolite crystals grown on mesoporous silica.