STRUCTURAL AND SURFACE ACID BASE PROPERTIES OF HYDROTALCITE-DERIVED MGALO OXIDES CALCINED AT VARYING TEMPERATURES/

This paper describes the influence of calcination temperature on bulk and surface properties of MgAlO binary oxide derived from the hydrotal cite precursor. MAS(27)Al NMR revealed that significant phase transiti ons occurred in the samples calcined at 673, 873, and 1073 K. These tr ansitions seem to be important in determining the surface acid/base pr operties of the samples. Microcalorimetric adsorptions of NH3 and CO2 showed that the acidity of these samples decreases in the order: gamma -Al2O3 > 673 K > 873 K approximate to 1073 K, while the basicity follo ws the order: MgO > 873 K > 1073 K > 673 K. IR spectroscopy revealed t hat the surface acid/base sites of the calcined hydrotalcite samples a re mainly Lewis type. (C) 1998 Academic Press.