Mechanochemically synthesized LiAlOx catalyst for aqueous aldol condensation of furfural with acetone

摘要

In the present study, the mechanochemical method is proposed for synthesis of LiAl-layered double hydroxides (LDHs). This method is eco-friendly and allows obtaining LiAl-LDH under relatively mild conditions (centripetal acceleration of milling bodies 300 m s-2) and in a short period of time (15 minutes). The structures of as-prepared LiAl-LDH, LiAl-mixed oxide (calcined LDH) and “activated” LiAl-LDH obtained after rehydration of the corresponding mixed oxide were confirmed by X-ray diffraction. The basicity of LiAlOx was measured by temperature-programmed desorption of CO2 and double isotherm technique. According to data obtained, LiAl-mixed oxide has a significant higher carbon dioxide adsorption capacity compared to MgAlmixed oxides prepared by conventional co-precipitation method. This indicates a large amount of basic surface sites with different strength (strong, medium and weak) for Li-containing systems. The formation of “activated” LiAl-LDH having Bronsted basic sites (OH groups in the interlayer space) provides an increased catalytic activity of LiAlOx in the reaction of aqueous-phase aldol condensation between furfural and acetone.