Cobalt-containing hexagonal mesoporous molecular sieves (Co-HMS): Synthesis, characterization and catalytic activity in the oxidation reaction of ethylbenzene

Cobalt-containing hexagonal mesoporous materials (Co-HMS and Co/HMS) with different cobalt content were synthesized for the first time by direct hydrothermal and post-synthesis (grafting) method. The materials were characterized in detail by X-ray diffraction, BET surface area, N2 sorption isotherms, SEM, TEM, UV–vis and XPS techniques. Powder X-ray diffraction pattern, N2 adsorption–desorption analysis and TEM analysis show the presence of hexagonal mesoporous structure, having Type IV isotherms and reveals the typical wormhole-like morphology. Spectroscopic techniques like UV–vis and XPS reveal cobalt in +2 oxidation state and tetrahedrally coordinated. Liquid phase oxidation of ethylbenzene using TBHP (70 wt%) as an oxidant shows that the catalysts are highly active, under solvent free conditions as well as under lower cobalt concentrations. Leaching studies performed by hot filtration experiments show that the cobalt catalysts prepared by hydrothermal methods are stable, while the grafted catalysts show the leaching of cobalt under the reaction conditions.

Graphical abstractCobalt-containing hexagonal mesoporous molecular sieves were prepared by direct hydrothermal method as well as by post-synthesis grafting method, for the first time. The catalyst shows excellent activity in the oxidation of ethylbenzene in presence of tert-butyl hydroperoxide oxidant, under solvent free conditions. Figure optionsDownload full-size imageDownload as PowerPoint slide