Cerium-incorporated cage-type mesoporous KIT-6 materials: Synthesis, characterization and catalytic applications

摘要

Ce-KIT-6 with Si/Ce = 5, 10, 20, 50, 100 and 150 mesoporous molecular sieves were successfully synthesized by a hydrothermal method. The synthesized materials were characterized extensively to understand the physico-chemical properties of the materials. The low-angle powder XRD patterns of calcined Ce-KIT-6 material showed a phase that can be indexed to cubic Ia3d. The UV-vis spectra of Ce-KIT-6 samples exhibited two distinct bands with maxima at 265 and 300 nm due to charge transfer to Ce~(3+) and Ce~(4+) respectively. Their intensity increased with increase in the Ce content of the samples. The BET surface area was found to be in the range of 668.4-836.9 m2/g. HR-TEM images revealed well-ordered cubic 3-D mesoporous channels. The catalytic activity was tested in the liquid phase oxidation of cyclohexane with hydrogen peroxide. Cyclohexanol was found to be the major product. Ce-KIT-6 (5) gave 74% cyclohexane conversion, which is higher than other catalysts. Ce4* is suggested to activate hydrogen peroxide by coordination to oxidise cyclohexane.