SYNTHESIS AND CHARACTERIZATION OF VARIOUS MGO AND RELATED SYSTEMS

Various magnesium oxide catalysts have been prepared by thermal treatm ent of two different precursors: Mg(OH)(2) and Mg-5(OH)(2)(CO3)(4). An additional system based on MgO and doped with B2O3 was also prepared. The textural and acid-base properties of the catalysts were investiga ted. The synthesized solids were characterized from adsorption isother ms, X-ray diffraction (XRD), H-1 MAS NMR, diffuse reflectance IR Fouri er transform spectroscopy (DRIFT) and temperature-programmed desorptio n-mass spectrometry (TPD-MS) of adsorbed probe molecules (pyridine, 2, 6-dimethylpyridine and carbon dioxide). The surface properties of the solids were found to be strongly influenced by the magnesium oxide pre paration conditions (viz. the precursor and calcination method used). Use of Mg(OH)(2) as the precursor and in vacuo calcination provided hi ghly basic solids (those with the highest proportions of strong basic sites). Various types of Lewis-acid sites were observed in the catalys ts prepared in vacuo, probably as the result of the presence of Mg2+ c ations of low coordination after the calcination.