Selective Production of Propylene from Methanol Conversion over Nanosized ZSM-22 Zeolites

One dimensional pore zeolites such as ZSM-22 (TON) are potential catalysts for hydrocarbon conversion reactions, including methanol-to-propylene (MTP) reaction. Different crystal lengths of ZSM-22 zeolite were prepared and examined for the MTP reaction. Nanosized TON zeolites with crystal length of ∼100 nm were synthesized by dynamic hydrothermal synthesis. The zeolite crystal length was tuned by using ethylene glycol as crystal growth modifier. The crystal lengths of ZSM-22 zeolites (approximately 100 and 300 nm) were confirmed from FE-SEM and TEM micrographs. However, the textural properties such as BET surface area and crystallinity of crystals were fairly similar. The effect of ZSM-22 crystal length on catalytic activity and propylene yields in the methanol-to-propylene reaction was investigated. The TON nanocrystals resulted in a higher propylene yield and better catalytic stability compared to the submicrometer zeolite (∼300 nm). Deactivation was observed for all catalysts. However, longer lifetime was observed for the nanosized ZSM-22 with crystal length of ∼100 nm.