The synthesis of Zn-Al hydrotalcites under different conditions and testing in aldol condensation

Abstract

The Zn-Al hydrotalcites (materials with the layered structure) with constant molar ratio of Zn/Al 2:1 were synthesized by co-precipitation method under different reaction conditions, such as pH, the concentration of ions, temperature throughout co-precipitation, the intensity of stirring, etc. The mixed oxides were formed from hydrotalcites by calcination at 450 °C. All synthesized materials were characterized by X-ray diffraction, thermogravimetric analysis, and via the specific surface area. The influence of the synthesis conditions on the crystallite size and specific surface area were studied. The formation of hydrotalcites as well as mixed oxides was confirmed by X-ray diffraction. The mixed oxides chosen were rehydrated, which enabled to restore their layered structure. Both mixed oxides and rehydrated (mixed) oxides were tested in the aldol condensation of furfural, resulting in finding that the rehydration would decrease the conversion of furfural when using all the rehydrated mixed oxides.