Catalytic properties of magnesium oxides doped with sodium compounds

Abstract

The physicochemical properties and catalytic activity of MgO doped with sodium compounds that are readily decomposed into sodium or sodium oxides have been examined. By calcination of the MgO doped with such sodium compounds as NaBH₄, NaNH₂ and NaNO₃ at 500 or 700 °C in a flowing inactive gas the basic strength of the MgO increased and the concentration of the basic sites attained a maximum at a loading of 1–3 wt % of sodium. The surface area of the MgO was decreased by the doping of sodium, especially when NaNO₃ was the dopant. The cause of the decrease in surface area was ascribable to the sintering effect by sodium on MgO owing to compound formation between MgO and sodium or its compounds. On the other hand, the concentration of one-electron donor centres was a minimum at a loading of ca. 2 wt % of sodium, which was inferred as the cause of both the adsorption of sodium on the centres and the migration of sodium on the MgO surface.

The dehydrogenation of cumene proceeds on the basic sites and its activity could be correlated with basic sites with pK_a > 15.0.