Mechanochemical Approach to Preparation of MFI Zeolites Substituted Isomorphously by Both Al and Fe as Durable Catalysts for the Dimethyl Ether to Olefin Reaction
Mizuho Yabushita, Hiroki Kobayashi, Ryota Osuga, Masafumi Nakaya, Masaki Matsubara, Sachiko Maki, Kiyoshi Kanie, Atsushi Muramatsu
Abstract
Zeolites with an MFI-type framework topology containing both Al and Fe ([Al, Fe]-MFI) atoms were prepared via a two-step mechanochemically assisted method. In the first step, reactions between SiO2 and either α-Fe2O3 or γ-AlO(OH), induced by mechanical force during planetary ball-milling, produced one of the two types of amorphous composites. A second hydrothermal treatment of a mixture of these composites yielded the [Al, Fe]-MFI zeolites. The thus-prepared [Al, Fe]-MFI zeolites exhibited a longer lifetime in the catalytic conversion of dimethyl ether into light olefins, compared to zeolites prepared via the conventional one-pot hydrothermal process using homogeneous reagents. Extraframework Fe species were absent and Fe atoms were well distributed throughout the MFI zeolite prepared via the two-step process, while the conventionally prepared zeolites contained extraframework Fe species. The better homogeneity of Fe atoms in the zeolite catalyst achieved by the mechanochemically assisted method led to a longer catalyst lifetime.