Cerium containing mcm-41-type mesoporous materials and their acidic and redox catalytic properties

The syntheses of cerium containing MCM-41 mesoporous molecular sieves (Ce-MCM-41) were carried out using different hydrothermal methods. However, the Ce-MCM-41 samples were mainly prepared by refluxing the gel mixture at atmospheric pressure under stirring adsorption, diffuse reflectance UV-visible (UV-vis) spectroscopy, IR spectroscopy, solid state magic-angle spinning nuclear magnetic resonance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry (EDX), transmission electron microscopy and thermogravimetric analyses of the samples reveal that well-ordered MCM-41-type mesoporous materials were prepared and Ce is incorporated presumably into the framework position and/or into the walls of silica matrix of MCM-41 structure. The EDX analyses of the samples confirm the presence of Ce in the Ce-MCM-41 samples. Typical XRD patterns of MCM-41-type hexagonal structures and high BET surface areas (983-1414 m² g^-1) with isotherms of type IV of these materials indicate the presence of hexagonal mesopores in the samples. The presence of a strong absorption band centered at ca. 300 nm and the absence of any absorption band at ca. 400 nm in the diffuse reflectance UV-vis spectra indicate the presence of tetra-coordinated cerium in the silica network of Ce-MCM-41 samples. The Ce-MCM-41 samples are active as catalysts for vapor-phase dehydration of cyclohexanol to cyclohexene and hydroxylation of 1-naphthol with aqueous H₂O₂ and tert-butyl hydroperoxide.