The role of the acidity of alumina prepared by aluminum-carbon black composite for CO hydrogenation to dimethyl ether on hybrid Cu-ZnO-Al₂O₃/alumina

The effects of surface area and the acidity of mesoporous γ-Al₂O₃, which is prepared by calcining aluminum-carbon black composite (Al/CB) of the precipitated aluminum nitrate on carbon black at different weight ratios, were investigated to verify the roles of carbon black in the surface properties and stability of Cu-ZnO-Al₂O₃ for the direct synthesis of dimethyl ether (DME) from syngas. A high surface area of ∼100 m²/g with a large pore diameter of ∼25 nm originated from the occupied spaces of carbon black enhanced the dispersion of the active Cu-ZnO-Al₂O₃ particles by forming a strong and stable interaction with mesoporous solid acid γ-Al₂O₃ surfaces. The enhanced dispersion of copper-containing particles, being strongly interacted with the acid sites of the hybrid Cu-ZnO-Al₂O₃/Al₂O₃ catalyst using γ-Al₂O₃ prepared at an optimal Al/CB weight ratio of 10, is mainly responsible for the high CO conversion with a high yield to oxygenates and a suppressed aggregation of active copper species during the direct synthesis of DME from syngas.