On the Location and Accessibility of Active Acid Sites in MFI Zeolites Modified by Alkaline Treatment

Abstract

An MFI zeolite (Si/Al = 40) was desilicated by alkaline treatment in order to generate mesopores. Temperature, alkali concentration and treatment duration were adjusted to maximize mesoporosity while preserving the zeolite structure. Special attention was paid to the characterization of the strength and accessibility of the acid sites. The catalysts were tested in the isobutane/butene alkylation, a reaction that is typically catalyzed by zeolites but limited by coke deposition. Additionally, glycerol esterification with acetic acid was used as a test reaction due to the required participation of large pores. The results confirmed that mesopores were successfully generated in the MFI zeolite, and the diffusion through the solid was enhanced, but the active sites were mainly confined to the micropores.