Industrial & Engineering Chemistry Research, Vol.53, No.50, 19498-19505, 2014
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 similar to 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 (similar to 300 nm). Deactivation was observed for all catalysts. However, longer lifetime was observed for the nanosized ZSM-22 with crystal length of similar to 100 nm.