Guerbet reaction of methanol and ethanol catalyzed by CuMgAlO_x mixed oxides: Effect of M²⁺/Al³⁺ ratio

A series of hydrotalcite-like derived MgAlO_x (MA) and CuMgAlO_x (CMA) catalysts with various M²⁺/Al³⁺ molar ratios were prepared and evaluated by the aldol condensation reaction of formaldehyde and acetaldehyde and Guerbet reaction of methanol and ethanol, respectively. The acidity and the alkalinity as well as the surface copper species of catalysts were characterized by NH₃/CO₂-TPD, XPS, H₂-TPR and H₂-TPD techniques. The results show that the catalytic performance of Guerbet reaction of methanol and ethanol is related to the surface Cu⁰ species and the number of moderate basic sites. Increasing the specific surface area of Cu⁰ is beneficial to the dehydrogenation of methanol and ethanol to formaldehyde and acetaldehyde. The increase of the amount of moderate basic sites can promote the condensation reaction of formaldehyde and acetaldehyde.