The study of methanol-to-olefin over proton type aluminosilicate CHA zeolites

A series of proton-type aluminosilicate H/CHA zeolites with different Si/Al ratios have been synthesized, characterized and used as catalysts for the methanol-to-olefin (MTO) reaction. The structure and acidities of zeolites are characterized by various techniques such as Al-27 MAS NMR and in situ IR spectroscopy. It is found preparation procedures remarkably affect the incorporation of Al into the zeolite framework, and the low amount of Bronsted acid sites effectively mitigate the coking during the MTO process, resulting in prolonged catalytic stability at relatively low reaction temperatures. In situ IR spectroscopy indicates that methanol reacts with proton of H/CHA zeolites to form methoxy species at 373 K. The physisorbed methanol reacts with methoxy species at elevated temperatures, leading to the formation of methane. (C) 2007 Published by Elsevier Inc.