Single-Step Synthesis of Dimethyl Ether from Syngas over Nanoparticle-Derived Bifunctional Pd/CeO₂/Al₂O₃ Catalysts

The single-step syngas-to-dimethyl ether (STD) process offers both economic and technical advantages over the current two-step industrial process that utilizes Cu/ZnO/Al₂O₃ catalysts. Here, we report a highly active bifunctional Pd/CeO₂/γ-Al₂O₃ catalyst, in which Pd colloids dispersed in a nanoscale CeO₂ matrix serve as the key building block for the methanol-active component, efficiently catalysing the STD reaction. For Pd/CeO₂/γ-Al₂O₃ with a high Pd-CeO₂ interface concentration, CO conversion and dimethyl ether yield are significantly increased compared to Pd supported on Al₂O₃. Systematic investigations using spectroscopic and microscopic techniques reveal the formation of highly dispersed palladium clusters/particles confined within the nanoparticulate CeO₂ matrix. The superior catalytic performance in both activity and stability observed for the Pd/CeO₂/γ-Al₂O₃ in the STD reaction stems from the active cationic palladium interfacial species and the presence of adjacent O vacancies.