Methanol Conversion on MFI Zeolites Obtained in Fluoride Medium: Effect of Silicon Source

The work is aimed at a fundamental study of the formation of acid sites in MFI zeolites obtained in a fluoride medium using Aerosil, silica gel, and silica sol as sources of silicon. The synthesized samples have been characterized by a set of instrumental methods and tested in the reaction of methanol conversion to hydrocarbons. It has been shown that the synthesis of MFI zeolite in a fluoride medium leads to the insertion of aluminum into the tetrahedral positions of the zeolite framework to form isolated acid sites. Moreover, the type of amorphous source of silicon affects both the amount of incorporated aluminum and the size of the product crystals. It has been established that the use of silica sol as a silicon source leads to an increase in the catalyst time-on-stream stability and a decrease in the selectivity for ethylene. The obtained result is explained by an increase in the proportion of Al atoms localized in zeolite channels.