Gas-phase epoxidation of propylene through radicals generated by silica-supported molybdenum oxide

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• 作者：Zhaoxia Song ; Naoki Mimura ; Juan J. Bravo-Suá ; rez ; Tomoki Akita ; Susumu Tsubota ; S. Ted Oyama
• 关键词：Epoxidation ; Propylene oxide ; Silica-supported molybdenum oxides ; Post-catalytic reaction ; Radical reaction
• 刊名：Applied Catalysis A ; General
• 出版年：2007
• 期刊代码：4_0926860x
• 类别：ch
• 出版时间：10 January 2007
• 卷：316
• 期：2
• 页码：142-151
• 文件大小：879 K

摘要

It was found that silica-supported molybdenum oxide was high effective for the epoxidation of propylene among various silica-supported metal oxides. The post-catalytic bed volume played an important role in its formation. On a MoO_x/SiO₂ with 0.255 mmol/g-SiO₂, a propylene conversion of 17.6%and a PO selectivity of 43.6%were obtained at 5 atm, 573 K and flow rates of C₃H₆/O₂/He = 10/5/10 cm³ min⁻¹. The characterization studies indicated that crystalline MoO₃ nano-particle species was more effective for propylene epoxidation to PO than molecularly dispersed Mo oxide species. The reaction mechanism of propylene epoxidation on MoO_x/SiO₂ catalysts is hypothesized to involve gas-phase radicals generated at relatively low temperature by the dispersed molybdenum oxide species. These radicals participated in homogeneous reactions with molecular oxygen to produce propylene oxide.