Structural Defects and Acidic and Basic Sites in Sol−Gel MgO

MgO prepared with the sol−gel technique had crystalline structure defects, obtained from X-ray powder diffraction and crystalline structure refinement, that correlated with its acidic and basic sites. The acidic sites, measured by adsorbing pyridine and NH 3, were found when brucite and MgO coexisted, which only occurred after annealing the sample at 673 K. Two different basic sites, measured by adsorbing CO 2, were present in a total concentration of about 10 21 sites per gram. These sites correlated to the presence of magnesium vacancies in MgO crystal. Both basic site and magnesium vacancy concentrations diminished when the sample annealing temperature was increased.