Surface Properties of Hydrotalcite-Based Zn(Mg)Al Oxides and Their Catalytic Activity in Aldol Condensation of Furfural with Acetone

Basic mixed oxides MgAl, ZnMgAl, and ZnAl were successfully prepared from hydrotalcite precursors synthesized by urea method. Materials with the same molar ratio (M2+/Al3+) = 2 were studied to describe the influence of Mg/Zn ratio on their physicochemical properties. Materials were tested as catalysts of the aldol condensation of furfural with acetone. For samples with similar particle sizes and surface BET areas, the varying catalytic activity was related to the different acidobasic properties. Higher furfural conversion and selectivity to longer carbon chain F2Ac product was observed for samples with higher total amount of basic sites. More specifically, it correlated with the population of Me2+-O2- pairs that represented dominant type of basic sites in all studied catalysts. At the same Al loading, Mg2Al mixed oxide exhibited higher specific surface area, higher total amount of basic sites and higher amount of acid sites than Zn2Al oxide.