Mechanochemical Approach to Preparation of MFI Zeolites Substituted Isomorphously by Both Al and Fe as Durable Catalysts for the Dimethyl Ether to Olefin Reaction

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 SiO 2 and either α-Fe 2 O 3 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.

New avenues for mechanochemistry in zeolite science

“…In the most recent example, aluminium and iron were incorporated into MFI zeolite, resulting in durable catalysts for the DTO (dimethyl ether-to-olefin) reactions. 80 The authors determined once again the optimal conditions for all necessary steps (milling, ageing, hydrothermal synthesis) and succeeded in the preparation of catalytically active materials without often occurring impurity phases like extra-framework species of iron.…”

Clarification of acid site location in MSE-type zeolites by spectroscopic approaches combined with catalytic activity: comparison between UZM-35 and MCM-68

“…Hence, controlling the location of the Al atoms during the crystallization process of zeolite has been extensively tackled, 4 which is oftentimes achieved by selecting the organic structure-directing agents (OSDAs) [5][6][7][8][9][10] with inorganic cations and/or the starting materials. [11][12][13][14] Recently, we have also achieved the successful control of the location of Al atoms in MFI [5][6][7] and CHA 11,12 frameworks. The presence or absence of Na + with OSDAs gave the different framework Al distributions in the MFI-type framework.…”

“…However, the control of the acid site location in the MSE-type structure has not been achieved yet. In general, the control of the position of the framework Al atoms in zeolite structure is achieved by tuning various parameters: [5][6][7][8][9][10][11][12][13][14] Si and/or Al source, inorganic agents, OSDAs, etc. In contrast, the location of the acid site in MSEtype zeolites cannot be controlled in a similar way to other zeolite topologies because the synthesizable gel composition is limited to an extremely narrow range.…”

Mechanochemical NaCl–Mediated Synthesis of Porous CuxMo1–xOy Catalyst for Knoevenagel Condensation

“…25 In addition, Mo 2 C, MoS 2 , MoB, MoSi 2 have exhibited excellent activity in the Knoevenagel condensation reaction. 26 To date, mechanochemical synthesis has shown excellent capabilities in preparing porous materials, such as carbon, 27,28 zeolites, 29,30 metal−organic frameworks (MOF), 31,32 covalent organic frameworks (COF), 33,34 and metal oxides. 35−38 Meanwhile, much attention has been focused on NaCl as a solvent or template, because of its good solid-state solubility.…”

“…To date, mechanochemical synthesis has shown excellent capabilities in preparing porous materials, such as carbon, , zeolites, , metal–organic frameworks (MOF), , covalent organic frameworks (COF), , and metal oxides. − Meanwhile, much attention has been focused on NaCl as a solvent or template, because of its good solid-state solubility. In 2008, Yang et al prepared hierarchically microporous, mesoporous, and even macroporous MOFs, using NaCl as a solid solvent and template via mechanochemical synthesis.…”