Catalytic activity for direct CO₂ hydrogenation to dimethyl ether with different proximity of bifunctional Cu-ZnO-Al₂O₃ and ferrierite

Dimethyl ether (DME) can be directly synthesized by carbon dioxide (CO₂) hydrogenation over bifunctional catalysts, which are suffered from various deactivation mechanisms caused by incompatible integrations of metal oxides and solid acid zeolites according to their different proximity. The core-shell structured integrations of Cu-ZnO-Al₂O₃ metal oxide (CZA) and ferrierite zeolite (FER) are investigated for direct CO₂ hydrogenation to DME. The detrimental and undesired surface properties formed by a possible ion-exchange of FER surfaces with the relatively volatile metal ions from Cu-ZnO-Al₂O₃ surfaces were effectively suppressed by applying the physically-coated interlayers with SiO₂ (CZA@FER) compared to the powder-mixed one (CZA/FER), where an intimate proximity of metal oxides and FER was eventually responsible for an increased CO selectivity and deactivation rate. The SiO₂ interlayers to isolate the CZA and FER with a suppressed migration of metal ions to FER surfaces further stabilized the active Cu-ZnO nanoparticles and acidic sites of FER surfaces.