A novel hydrofobic niobium oxyhydroxide as catalyst: Selective cyclohexene oxidation to epoxide

A surface modified niobium oxyhydroxide catalyst was utilized for the selective liquid-phase oxidation of cyclohexene to epoxide in the presence of hydrogen peroxide. After surface modification with a surfactant (cetiltrimetilamonium bromide-CTAB), the very active niobium oxyhydroxide (NbO2OH), presented hydrophobic characteristics and good activity for the oxidation of cyclohexene over the heterogeneous catalyst. Furthermore, the hydrophobic material presented a high selectivity toward the formation of the epoxide species. The mass spectrometry analysis of the reaction showed that epoxide species was produced with a selectivity of 60% using 0.2 mL of hydrogen peroxide, with 65% of conversion. The results strongly suggest that the reaction involves oxidizing species generated after the reaction with H2O2. The surfactant anchored over the niobium catalyst promotes a better interaction with the nonpolar substrate. (C) 2013 Elsevier B.V. All rights reserved.