Active Fe-and Mn-loaded MCM-41(Fe–Mn/MCM-41),which was synthesized via a hydrothermal reaction followed by impregnation,is used in the heterogeneous Fenton reaction to degrade methyl orange(MO) in aqueous solution. T...Active Fe-and Mn-loaded MCM-41(Fe–Mn/MCM-41),which was synthesized via a hydrothermal reaction followed by impregnation,is used in the heterogeneous Fenton reaction to degrade methyl orange(MO) in aqueous solution. The synthesized samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,N_2 adsorption–desorption isotherm analysis,Fourier transform infrared spectroscopy,and X-ray photoelectron spectroscopy. Compared with Fe/MCM-41 and Mn/MCM-41,Fe–Mn/MCM-41 showed higher activity for MO degradation and mineralization. Effects of various operating parameters,such as pH,Mn content,and H_2O_2 dosage,on the degradation process were subsequently investigated. Results of experiments on the effect of radical scavengers revealed that the degradation of MO could be attributed to oxidation by HO_·. The synergy of Fe and Mn species in the Fenton oxidation process was also explained.展开更多
MCM-41 was synthesized by a soft template technique.The specific surface area and pore volume of the MCM-41 were 805.9 m2/g and 0.795 cm3/g,respectively.MCM-41-supported manganese and cobalt oxide catalysts were prepa...MCM-41 was synthesized by a soft template technique.The specific surface area and pore volume of the MCM-41 were 805.9 m2/g and 0.795 cm3/g,respectively.MCM-41-supported manganese and cobalt oxide catalysts were prepared by an impregnation method.The energy dispersive X-ray spectroscopy clearly confirmed the existence of Mn,Co,and O,which indicated the successful loading of the active components on the surface of MCM-41.The structure and function of the catalysts were changed by modulating the molar ratio of manganese to cobalt.The 10%MnCo(6:1)/MCM-41(Mn/Co molar ratio is 6:1)catalyst displayed the best catalytic activity according to the activity evaluation experiments,and chlorobenzene(1000 ppm)was totally decomposed at 270°C.The high activity correlated with a high dispersion of the oxides and was attributed to the exposure of more active sites,which was demonstrated by X-ray diffraction and high-resolution transmission electron microscopy.The strong interactions between MnO2,Co3O4,MnCoOx,and MCM-41 indicated that cobalt promoted the redox cycles of the manganese system.The bimetal-oxide-based catalyst showed better catalytic activity than that of the single metal oxide catalysts,which was further confirmed by H2 temperature-programmed reduction.Chlorobenzene temperature-programmed desorption results showed that 10%MnCo(6:1)/MCM-41 had higher adsorption strength for chlorobenzene than that of single metal catalysts.And stronger adsorption was beneficial for combustion of chlorobenzene.Furthermore,10%MnCo(6:1)/MCM-41 was not deactivated during a continuous reaction for 1000 h at 260°C and displayed good resistance to water and benzene,which indicated that the catalyst could be used in a wide range of applications.展开更多
A secondary amino-modified mesoporous molecular sieve MCM-41 was obtained by reaction of bis(3-(triethoxysilyl)propyl)amine with MCM-41. The chiral Salen-Mn (III) complex was anchored onto the modified MCM-41 by a mul...A secondary amino-modified mesoporous molecular sieve MCM-41 was obtained by reaction of bis(3-(triethoxysilyl)propyl)amine with MCM-41. The chiral Salen-Mn (III) complex was anchored onto the modified MCM-41 by a multi-step grafting method and two heterogenized catalysts with different Mn contents were obtained. The catalysts were characterized by XRD, N2 adsorption, ICP, FT-IR and DR UV-Vis. Their catalysis on asymmetric epoxidation of several olefins was studied with NaClO and m-CPBA as oxidants respectively. It was found that both the activity and enantioselectivity of the cata- lysts decreased after the homogeneous catalyst was heterogenized. The reasons resulting in the de- crease of catalytic performance were discussed.展开更多
基金supported by the National Basic Research Program of China ("973" Program, No. 2012CB720302)Program for Changjiang Scholars and the Innovative Research Team in Universities (No. IRT0936)
文摘Active Fe-and Mn-loaded MCM-41(Fe–Mn/MCM-41),which was synthesized via a hydrothermal reaction followed by impregnation,is used in the heterogeneous Fenton reaction to degrade methyl orange(MO) in aqueous solution. The synthesized samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,N_2 adsorption–desorption isotherm analysis,Fourier transform infrared spectroscopy,and X-ray photoelectron spectroscopy. Compared with Fe/MCM-41 and Mn/MCM-41,Fe–Mn/MCM-41 showed higher activity for MO degradation and mineralization. Effects of various operating parameters,such as pH,Mn content,and H_2O_2 dosage,on the degradation process were subsequently investigated. Results of experiments on the effect of radical scavengers revealed that the degradation of MO could be attributed to oxidation by HO_·. The synergy of Fe and Mn species in the Fenton oxidation process was also explained.
文摘MCM-41 was synthesized by a soft template technique.The specific surface area and pore volume of the MCM-41 were 805.9 m2/g and 0.795 cm3/g,respectively.MCM-41-supported manganese and cobalt oxide catalysts were prepared by an impregnation method.The energy dispersive X-ray spectroscopy clearly confirmed the existence of Mn,Co,and O,which indicated the successful loading of the active components on the surface of MCM-41.The structure and function of the catalysts were changed by modulating the molar ratio of manganese to cobalt.The 10%MnCo(6:1)/MCM-41(Mn/Co molar ratio is 6:1)catalyst displayed the best catalytic activity according to the activity evaluation experiments,and chlorobenzene(1000 ppm)was totally decomposed at 270°C.The high activity correlated with a high dispersion of the oxides and was attributed to the exposure of more active sites,which was demonstrated by X-ray diffraction and high-resolution transmission electron microscopy.The strong interactions between MnO2,Co3O4,MnCoOx,and MCM-41 indicated that cobalt promoted the redox cycles of the manganese system.The bimetal-oxide-based catalyst showed better catalytic activity than that of the single metal oxide catalysts,which was further confirmed by H2 temperature-programmed reduction.Chlorobenzene temperature-programmed desorption results showed that 10%MnCo(6:1)/MCM-41 had higher adsorption strength for chlorobenzene than that of single metal catalysts.And stronger adsorption was beneficial for combustion of chlorobenzene.Furthermore,10%MnCo(6:1)/MCM-41 was not deactivated during a continuous reaction for 1000 h at 260°C and displayed good resistance to water and benzene,which indicated that the catalyst could be used in a wide range of applications.
基金Supported by the National Natural Science Foundation of China (Grant No. 20376017)
文摘A secondary amino-modified mesoporous molecular sieve MCM-41 was obtained by reaction of bis(3-(triethoxysilyl)propyl)amine with MCM-41. The chiral Salen-Mn (III) complex was anchored onto the modified MCM-41 by a multi-step grafting method and two heterogenized catalysts with different Mn contents were obtained. The catalysts were characterized by XRD, N2 adsorption, ICP, FT-IR and DR UV-Vis. Their catalysis on asymmetric epoxidation of several olefins was studied with NaClO and m-CPBA as oxidants respectively. It was found that both the activity and enantioselectivity of the cata- lysts decreased after the homogeneous catalyst was heterogenized. The reasons resulting in the de- crease of catalytic performance were discussed.
