Rapid solvent-free synthesis of nano-sized ZSM-5 with a low Si/Al ratio at 90 °C

Abstract

Nano-sized ZSM-5 zeolites with wide framework Si/Al ratios are highly desired in the petrochemical and other fields, whereas their synthesis suffers from cost, efficiency and environmental issues. Herein, a new protocol is proposed for the rapid synthesis of ZSM-5 with a low Si/Al ratio at a low temperature. That is, preparing a solid mixture by grinding solid raw materials with a liquid seed and crystallizing the mixture under solvent-free conditions at 90 °C. It is proved that the liquid seed not only accelerates the zeolite crystallization but also boosts the incorporation of Al into the zeolite framework. It is found that the ZSM-5 zeolite with a Si/Al ratio of 36 and an ultra-small crystal size (ca. 25 nm) can be synthesized within 30 hours at 90 °C and a framework Si/Al ratio of 28 can be reached at this temperature in this way. This ZSM-5 zeolite exhibited better catalytic performance in the reaction of methanol to olefins compared to that synthesized by the conventional hydrothermal method.