Innovative ZSM-5-based catalyst design via 3D printing for methanol dehydration to DME

Abstract

In the last years, the use of 3D printing for the preparation of structured materials with catalytic functionalities has attracted considerable interest. In this work, using ZSM-5 zeolite as acidity provider, we explore two routes that employ additive manufacturing to prepare structured catalysts for dimethyl ether production via methanol dehydration. In the first route, ZSM-5-based monoliths are 3D-printed using crystalline ZSM-5 powder and bentonite clay as a binder. In the second route, α-alumina support structures are first fabricated via robocasting, followed by in situ hydrothermal synthesis of ZSM-5 on the printed structures. The structured catalysts along with their starting materials are characterized by N₂ adsorption, XRD, pyridine-FTIR, electron microscopy, while stress–strain curves are also obtained to evaluate the monoliths' mechanical stability. The structured catalyst prepared via the first route adequately retains the physicochemical properties of the ZSM-5 crystallites. Via the second route, ZSM-5 crystallites with good porosity and acidity are grown on the 3D printed α-Al₂O₃ support, achieving a total loading of ca. 4 wt%. When compared on an equivalent ZSM-5 basis, the ZSM-5/α-Al₂O₃ catalyst exhibits up to twice the activity in methanol conversion with 100 C-mol% DME selectivity, while it also outperforms the corresponding hydrothermally prepared ZSM-5 powder. This is possibly linked to the excellent dispersion of the ZSM-5 active sites on the 3D-printed α-Al₂O₃ structure, which provides a unique substrate for the growth of surface ZSM-5 nano-crystallites. This work highlights the great potential of employing 3D printing techniques for catalytic applications.