Amorphization effects on the basic sites of nanometric magnesium oxide.

Abstract

The paper reports the catalytic action of the basic sites of nanocrystalline particles of rare earth-doped magnesium oxide in the aldolization reaction between acetone and methanol leading to the C–C bond formation of an a,b-unsaturated compound (methyl vinyl ketone), also forming methyl ethyl ketone and isopropyl alcohol. Undoped and doped MgO samples were prepared by high-energy mechanical milling of commercial Mg, Y and Ce oxide powders. Catalytic activity and surface basicity of these compounds were strongly influenced by doping and the time of mechanical milling (amorphization process). Such milling leads to the formation of nanocrystalline materials. Influence of mechanical processing of these compounds was investigated by means of N2 adsorption (BET), X-ray diffraction (XRD), TEM, CO2 chemisorption and room temperature photoluminescence emission. Strong changes of polar groups such as hydroxyl groups on the surface of the solid were directly related to the photoluminescence emission observed.