In this study,Mn-Na_(2)WO_(4)/γ-Al_(2)O_(3) catalysts with varying ratios of Mn/W were prepared using the dry impregnation method.These catalysts were then tested for their suitability in the oxidative coupling of me...In this study,Mn-Na_(2)WO_(4)/γ-Al_(2)O_(3) catalysts with varying ratios of Mn/W were prepared using the dry impregnation method.These catalysts were then tested for their suitability in the oxidative coupling of methane reaction.The X-ray photoelectron results revealed the presence of the tetrahedral WO_(4)^(2–)phase in all prepared catalysts.It is believed that the presence of this phase is associated with high catalyst activity,indicating the potential of the catalysts for the desired reaction.The activity results show that the catalyst with a high Mn/W ratio exhibited higher activity at 800℃,whereas the catalyst with a low Mn/W ratio showed greater activity at 850℃.This suggests that the Mn/W ratio influences the reaction temperature at which the catalyst is most active.Furthermore,the X-ray diffraction results of the treated catalysts revealed that the catalyst with a high Mn/W ratio exhibited more MnAl_(2)O_(4) at 800℃,whereas the catalyst with a low Mn/W ratio contained more MnWO_(4) at 850℃.The results suggest that the presence of MnAl_(2)O_(4) sites may promote a more facile Mn^(2+)↔Mn^(3+)cycle at lower temperatures than the MnWO_(4) site,potentially contributing to the enhanced catalyst activity in the oxidative coupling of methane reaction at 800℃.展开更多
By calcinating commercial silica gel at 1500℃or adding Na2C2O4 and then calcinating at 850℃,α cristobalite was formed.On the basis of the vibration spectroscopy of silica support,Na W Mn/SiO2 catalyst was character...By calcinating commercial silica gel at 1500℃or adding Na2C2O4 and then calcinating at 850℃,α cristobalite was formed.On the basis of the vibration spectroscopy of silica support,Na W Mn/SiO2 catalyst was characterized by Raman spectroscopy.The results show that the structure of support and the interaction among metal components have significant effect on the dispersion and the structure of metal sites,and the tetrahedrally coordinated formed on α cristobalite surface is the most possible site of methane activation with high C2 selectivity.展开更多
基金support of the Ferdowsi University of Mashhad Research Council,Mashhad,Iran(Grant No.68841)and(OCM project No.23346).
文摘In this study,Mn-Na_(2)WO_(4)/γ-Al_(2)O_(3) catalysts with varying ratios of Mn/W were prepared using the dry impregnation method.These catalysts were then tested for their suitability in the oxidative coupling of methane reaction.The X-ray photoelectron results revealed the presence of the tetrahedral WO_(4)^(2–)phase in all prepared catalysts.It is believed that the presence of this phase is associated with high catalyst activity,indicating the potential of the catalysts for the desired reaction.The activity results show that the catalyst with a high Mn/W ratio exhibited higher activity at 800℃,whereas the catalyst with a low Mn/W ratio showed greater activity at 850℃.This suggests that the Mn/W ratio influences the reaction temperature at which the catalyst is most active.Furthermore,the X-ray diffraction results of the treated catalysts revealed that the catalyst with a high Mn/W ratio exhibited more MnAl_(2)O_(4) at 800℃,whereas the catalyst with a low Mn/W ratio contained more MnWO_(4) at 850℃.The results suggest that the presence of MnAl_(2)O_(4) sites may promote a more facile Mn^(2+)↔Mn^(3+)cycle at lower temperatures than the MnWO_(4) site,potentially contributing to the enhanced catalyst activity in the oxidative coupling of methane reaction at 800℃.
文摘By calcinating commercial silica gel at 1500℃or adding Na2C2O4 and then calcinating at 850℃,α cristobalite was formed.On the basis of the vibration spectroscopy of silica support,Na W Mn/SiO2 catalyst was characterized by Raman spectroscopy.The results show that the structure of support and the interaction among metal components have significant effect on the dispersion and the structure of metal sites,and the tetrahedrally coordinated formed on α cristobalite surface is the most possible site of methane activation with high C2 selectivity.
