This study reports the synthesis of size-controlled Fe-MFI （Fe-substituted zeolites with the MFI topology） and their catalytic performances for DTO （dimethyl ether-to-olefins） reaction. The amount of HC1 and aging...This study reports the synthesis of size-controlled Fe-MFI （Fe-substituted zeolites with the MFI topology） and their catalytic performances for DTO （dimethyl ether-to-olefins） reaction. The amount of HC1 and aging temperature were decisive factors to control the particle size of Fe-MFI in the range of 50 nm to 600 nm. The introduction of Fe3＋ ions into the zeolitic framework was confirmed by UV （ultraviolet）-visible spectroscopy. In addition, it was observed that the strength of acid site in prepared Fe-MFI was weaker than that of commercial ZSM-5. With decrease in the particle size, the amount of deposited coke decreased so that the catalyst life for the DTO reaction was well promoted. The present catalysts showed the higher light-olefin selectivity （C2= ＋ C3= ＋ C4=） than commercial ZSM-5 catalysts mainly due to the suppression of the formation of paraffins; however, the Fe-MFI catalysts were deactivated rapidly because of their low activity for the cracking of alkenes.展开更多
The α-Fe nanoparticles with oxide shell were prepared by the complete reduction of iron oxide ones with hydrogen, followed by the selective surface oxidation as a thin layer. As-treated α-Fe nanoparticles preserved ...The α-Fe nanoparticles with oxide shell were prepared by the complete reduction of iron oxide ones with hydrogen, followed by the selective surface oxidation as a thin layer. As-treated α-Fe nanoparticles preserved their saturation magnetization and metal α-Fe phase for at least 80 days in the air. In comparison, the unstabilized α-Fe nanoparticles protected only by their silica shell were oxidized instantly in the air and the saturation magnetization of the unstabilized α-Fe nanoparticles was decreased drastically. Since the stabilization procedure was carried out under dry conditions using silica-coated iron oxide nanoparticles as precursors, it could be applied to nanoparticles of various sizes and shapes to obtain a stable α-Fe phase.展开更多
文摘This study reports the synthesis of size-controlled Fe-MFI （Fe-substituted zeolites with the MFI topology） and their catalytic performances for DTO （dimethyl ether-to-olefins） reaction. The amount of HC1 and aging temperature were decisive factors to control the particle size of Fe-MFI in the range of 50 nm to 600 nm. The introduction of Fe3＋ ions into the zeolitic framework was confirmed by UV （ultraviolet）-visible spectroscopy. In addition, it was observed that the strength of acid site in prepared Fe-MFI was weaker than that of commercial ZSM-5. With decrease in the particle size, the amount of deposited coke decreased so that the catalyst life for the DTO reaction was well promoted. The present catalysts showed the higher light-olefin selectivity （C2= ＋ C3= ＋ C4=） than commercial ZSM-5 catalysts mainly due to the suppression of the formation of paraffins; however, the Fe-MFI catalysts were deactivated rapidly because of their low activity for the cracking of alkenes.
文摘The α-Fe nanoparticles with oxide shell were prepared by the complete reduction of iron oxide ones with hydrogen, followed by the selective surface oxidation as a thin layer. As-treated α-Fe nanoparticles preserved their saturation magnetization and metal α-Fe phase for at least 80 days in the air. In comparison, the unstabilized α-Fe nanoparticles protected only by their silica shell were oxidized instantly in the air and the saturation magnetization of the unstabilized α-Fe nanoparticles was decreased drastically. Since the stabilization procedure was carried out under dry conditions using silica-coated iron oxide nanoparticles as precursors, it could be applied to nanoparticles of various sizes and shapes to obtain a stable α-Fe phase.
