Epoxidation of dibenzocycloalkenes on Ti–Ge-MCM-41 and Ti-SBA-15 catalysts

Abstract

Epoxidation of a series of dibenzocycloalkenes: phenanthrene, 5H-dibenzo[ a, e]cycloheptene, 5H-dibenzo[ a, c] cycloheptene, 5,6-dihydrodibenzo[ a, e]cyclo-octene, and dibenzo[ a, e]cyclooctene with hydrogen peroxide was investigated on Ti- and Ge-modified Ti-incorporated-type mesoporous catalysts including MCM-41 and SBA-15 structures looking for the effect of the porous texture and Ge-promoting on both activity and selectivity to epoxide and H 2O 2 efficiency. Ti–Ge-MCM-41 catalysts (Si/Ti = 43; Si/Ge = 85 and Si/Ti = 41; Si/Ge = 62) were prepared by a one-pot surfactant-assisted procedure based on the use of a cationic surfactant (CTAB, cetyltrimethylammonium bromide), as structure directing agent, and a complexing polyalcohol (2,2′,2″-nitriletriethanol), able to harmonize the hydrolysis and co-condensation reaction rates of the different heteroelements and the self-assembling processes between the inorganic precursors and the surfactant micelles. Ti-SBA-15 catalysts were prepared in a strong acidic medium (2 M HCl solution) using Pluronic P-123 (HO(CH 2CH 2O) 20(CH 2CH(CH 3)O) 70(CH 2CH 2O) 20H),as surfactant and tetraethyl orthosilicate and tetrapropyl orthotitanate as silicon and titanium sources. All these materials were characterized by N 2 adsorption–desorption isotherm measurements, XRD, TEM and DR–UV–Vis, both as fresh and used catalysts.