Remarkable increasing of ZSM-5 lifetime in methanol to hydrocarbon reaction by post engineering in fluoride media

Abstract

Long lived methanol to hydrocarbon (MTH) catalyst was obtained by the post-engineering of ZSM-5 in FeF3/NH4HF2 media. Optimized Fe/ZSM-5 preparation can increase the lifetime of ZSM-5 by a factor of 10 under investigated conditions. The modified catalysts were subjected to detailed characterization including XRD, FT-IR, nitrogen adsorption, NH3-TPD and Mössbauer spectroscopy analyses to explore the performance improvement mechanism. The characterization results indicate the post-engineering step selectively diminishing Lewis acidity and internal hydroxyl produced by defect sites without extensively removing Al from ZSM-5 lattice as well as nano-sized FexOy entrapping in zeolite. The synergic effect of these modifications resulted in the reduction of coke species accumulation rate in zeolite and consequently long catalyst lifetime. The simple and effective nature of such post-engineering method make it become an interesting method for MTH reaction especially when combined with the fluoride processing infrastructure in existed fluoride industry.