Surface-to-volume ratio of synthesis reactor vessel governing low temperature crystallization of ZSM-5

Abstract

Zeolite ZSM-5 is one of the major catalysts in the petroleum and finechemical industries. The synthesis of zeolite ZSM-5 is usually carried out at a temperature above 100 °C using an immense amount of organic structuredirecting agents (OSDA). It is interesting to note that fine-tuning the initial gel mixture can be used to enhance the typical slow crystallization rate of ZSM-5. Herein, we report the effect of the surface-to-volume ratio of the reactor vessel on the crystallization of ZSM-5 at low temperature. The surface-to-volume ratio of the reactor vessel influences the heat-transfer during the synthesis, which further governs the crystallization of ZSM-5. It was found that the higher the surface-to-volume of the reactor, the more crystalline the resulting product. The products with the highest crystallinity exhibited a nearly spherical morphology composed of smaller ZSM-5 crystallites. This phenomenon allows the presence of inter-crystallite mesopores, which is an advantage for the catalytic reaction of bulky molecules.