Catalytic epoxidation of propylene over a Schiff-base molybdenum complex supported on a silanized mesostructured cellular foam

A Schiff-base molybdenum complex (MoO2-salen) supported on mesostructured cellular foam (MCF) was initially prepared by an in situ synthesis method under acidic conditions. Following silanization modification, a MoO2-salen@MCF-S sample with improved surface hydrophobicity was obtained. The ligand environment of molybdenum within the samples has been analyzed by Fourier-transform infrared spectroscopy, ultraviolet/visible spectroscopy, and X-ray photoelectron spectroscopy. Furthermore, the textural and structural properties of the corresponding materials have been characterized by nitrogen adsorption-desorption isotherms and transmission electron microscopy. Despite of the presence of fewer MoO(2)species, the results showed that MoO2-salen@MCF-S has more active Mo centers than MoO2-salen and MoO2-salen@MCF on the basis of maintaining the mesoporous structure. The catalytic performances of the synthesized samples were assessed in the epoxidation of propylene withtert-butyl hydroperoxide (TBHP) as an oxidant, and the mechanism of propylene epoxidation under MoO2-salen@MCF was given. The prepared MoO2-salen@MCF-S material showed the best epoxidation performance with 1,2-dichloroethane as a solvent and a molar ratio of propylene to TBHP of 10:1 at 120 degrees C, giving a TBHP conversion of up to 100% after 1 h, with selectivities for propylene oxide andtert-butyl alcohol reaching 94.7% and 84.6%, respectively.