Microcalorimetric Studies of Zn—Al Mixed Oxides Obtained From Hydrotalcite-type Precursors

A series of Zn–Al hydrotalcites with Zn/Al molar ratios of 1, 2, 3 and 6 were prepared by co-precipitation method. TG-DTG results showed that the hydrotalcites decompose in two stages, corresponding to the two endothermic peaks around 180 and 220°C. After calcination at 400°C, the samples were converted into Zn–Al mixed oxides with the only XRD pattern of ZnO, except for the sample with the ratio of 6. The Zn–Al mixed oxides possess similar surface acidity revealed by microcalorimetric adsorption of NH₃. The basicity of the samples increases with the order: ZnO>6Zn/Al>1Zn/Al>Al₂O₃.This revised version was published online in November 2005 with corrections to the Cover Date.