Synthesis of silicalite-1 by dry-gel conversion method: factors affecting its crystal size and morphology

Silicalite-1 crystals were synthesized from clear and diluted solutions by the dry-gel conversion method and the hydrothermal method was used as reference to do a comparative study. The effect of the structure-directing agent, silica source, aging time and crystallization time was investigated. Zeolite crystals, about 200-500 nm and 1 micron, were obtained by the liquid phase hydrothermal (LPH) and steam-assisted crystallization (SAC), called as dry-gel conversion method, respectively. The crystals were identified by XRD and SEM. The results show that the aging time and the water content are crucial in the synthesis of zeolites. Indeed, well formed zeolite crystals are obtained by the SAC technique using a lower amount of water than in the LPH method. However, the presence of the structure directing agent (SDA) into the dry gel determines the crystallization of silicalite-1.