Structure and Stability of Mg-HZSM-5/Al2O3 Catalysts for Synthesizing Olefins from DME: Effect of Thermal and Hydrothermal Treatments

Changes in the structural, textural, and acidic properties of Mg-HZSM-5/Al2O3 catalyst subjected to pretreatment (thermal and hydrothermal) of varying temperatures and durations are studied. The catalysts are characterized by XRF, XRD, Al-27 solid-state NMR spectroscopy, nitrogen adsorption, DRIFT spectroscopy, and ammonia TPD. The catalytic activity of the samples in converting dimethyl ether (DME) to lower olefins is studied. It is shown that the initial catalytic activity of an Mg-containing zeolite catalyst is determined by the total acidity of the surface and does not depend on the initial acid site strength distribution, while the stability of the catalyst depends on its morphological properties.