| Abstract
| - Lanthanum-doped MCM-48 molecular sieves with different La contents were synthesized hydrothermallyand characterized by X-ray diffraction (XRD), nitrogen sorption, transmission electron microscopy (TEM),UV−visible spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. The results show that themajority of La cations have been incorporated into the framework of MCM-48 molecular sieves. When themolar ratio of La/Si is >0.039 in the sample, some of lanthanum species exist in the extraframework. Comparedwith pure silicate MCM-48, lanthanum-doped MCM-48 samples show the medium strong acidity that is dueto the incorporation of La in the framework of silica. In the oxidation of styrene with H2O2 as the oxidantover the lanthanum-doped MCM-48 catalysts, benzaldehyde is the main product with a small amount ofstyrene oxide. The La content in the catalysts, reaction temperature, reaction time, and solvent affect greatlythe catalytic oxidation of styrene. The conversion of styrene and the selectivity to styrene oxide increasenoticeably when a small amount of NaOH aqueous solution is added into the reaction mixture. Ln-dopedMCM-48 catalysts with 14 kinds of rare earth elements were synthesized hydrothermally and evaluated forthe oxidation of styrene. The results show that their catalytic performance is tremendously different anddepends on the nature of rare earth elements doped in the MCM-48 mesoporous materials.
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