Study of MgO and Pt/MgO systems by XRD, TPR, and H-1 MAS NMR

We studied changes in magnesium oxide upon rehydration under operating cond itions similar to those used in the subsequent impregnation of a metal salt on its surface. The ensuing transformations were monitored by using the XR D, TPR, and H-1 MAS NMR techniques. On the basis of the results, magnesium oxide (periclase phase) is rehydrated to magnesium hydroxide (brucite phase ) and dehydrated back to periclase when the calcination temperature is rais ed to 600 degrees C. At this point, the transformation occurs simultaneousl y with changes in the textural and basic properties of the solid. Pt/MgO ca talysts prepared by impregnation of magnesium oxide exhibit variable metall ic and surface properties depending on whether Pt(NH3)(4)(NO3)(2) or H2PtCl 6 is used as the impregnating salt.