Hydrogenation of CO₂ to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

Eschewing the common trend toward use of catalysts composed of Cu, it is reported that PdZn alloys are active for CO₂ hydrogenation to oxygenates. It is shown that enhanced CO₂ conversion is achievable through the introduction of Brønsted acid sites, which promote dehydration of methanol to dimethyl ether. We report that deposition of PdZn alloy nanoparticles onto the solid acid ZSM-5, via chemical vapor impregnation affords catalysts for the direct hydrogenation of CO₂ to DME. This catalyst shows dual functionality; catalyzing both CO₂ hydrogenation to methanol and its dehydration to dimethyl in a single catalyst bed, at temperatures of >270 °C. A physically mixed bed comprising 5% Pd 15% Zn/TiO₂ and H-ZSM-5 shows a comparably high performance, affording a dimethyl ether synthesis rate of 546 mmol kg_cat^–1 h^–1 at a reaction temperature of 270 °C