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چکیده
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Manganese containing mesoporous molecular sieves, Mn-HMS and Mn-SBA-15, with different Si/Mn molar ratio was synthesized by direct incorporation method. The synthesized materials was characterized by various physicochemical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance ultraviolet–visible spectroscopy (DR-UV-VIS), SEM, TEM and BET surface area, N2 sorption isotherms. XRD, FTIR, and N2 sorption results show that the characteristic structural features of HMS and SBA-15 are preserved after manganese incorporation. The catalytic activity of manganese incorporated mesoporous molecular sieves Mn-HMS and Mn-SBA-15, was evaluated in the oxidation of benzyl alcohol in the liquid phase using tert-butylhydroperoxide (TBHP) as the oxidant. It was found that Mn-SBA-15 with Si/Mn=50 molar ratio is an efficient catalyst for the oxidation of benzyl alcohol and showed high selectivity to benzaldehyde. As we expected, the leaching of Mn from support during the reaction was negligible, because of strong interaction between Mn spices and structural features of mesopores. The effects of Mn loading and various solvents on the conversion and selectivity were studied. The activity of the Mn-SBA-15 catalyst differs with the type of the solvent and in this case, acetonitrile gives the best conversion results. The influences of reusability, and TBHP to benzyl alcohol molar ratio were investigated. Under optimized conditions 68.75% conversion of benzyl alcohol and 98% selectivity benzaldehyde were achieved.
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