Coupling of methanol and ethanol over CuMgAlOx catalysts: the roles of copper species and alkalinity

A series of CuMgAlOx mixed oxides with Cu content between 0 and 5mol%, were obtained by the calcination of hyrotalcite-like precursors. The catalytic activity was evaluated by the coupling of methanol and ethanol. The physical and chemical properties of the catalysts were characterized by XRD, TG, XPS, N2O titration, in situ CO-DRIFTS, XPS, H-2-TPR, NH3-TPD, and CO2-TPD techniques. The results show that with the increase of Cu content, the surface areas of exposed Cu species (Cu-0 and Cu+) and the hydrogen dissociation abilities of the reduced catalysts increase, while the amount of the moderately basic sites decreases. The catalytic performance shows that the conversions of methanol and ethanol are strongly related to the surface areas of exposed Cu species. The STY of Guerbet products (C3 and C4 alcohols, aldehydes) is closely related to the surface exposed Cu species and the moderately basic sites, and the CHT-3 catalyst has a maximum of 125.01gkg(-1) h(-1). Moreover, by-products including esters and CO2 also show a strong positive relationship with the surface areas of exposed Cu species.