催化作用
环氧丙烷
自动氧化
无机化学
碱金属
氧气
相(物质)
氧化物
多相催化
卤素
丙烯
化学
有机化学
环氧乙烷
聚合物
共聚物
烷基
作者
Sheima J. Khatib,S. Ted Oyama
标识
DOI:10.1080/01614940.2015.1041849
摘要
The direct oxidation of propylene to propylene oxide (PO) using molecular oxygen has many advantages over existing chlorohydrin and hydroperoxide process, which produce side products and require complex purification schemes. Recent advances in liquid-phase and gas-phase catalytic oxidation of propylene in the presence of only molecular oxygen as oxidant and in absence of reducing agents are summarized. Liquid-phase PO processes involving soluble or insoluble Mo, W, or V catalysts have been reported which provide moderate conversions and selectivities, but these likely involve autoxidation by homogeneous chain reactions. Gas-phase PO catalysts have been mostly Ag-, Cu-, or TiO2-based substances, although other compositions such as Au-, MoO3-, Bi-based catalysts and photocatalysts have also been suggested as possibilities. The Ag catalysts differ from those used for ethylene oxide production in having high Ag contents and numerous additives. The additives are solid-phase alkali metals, alkaline earth metals, and halogens, with the most common substances being NaCl and CaCO3. Nitrogen oxides in the form of gas-phase species or nitrates have also been found to be effective in enhancing PO production. Direct epoxidation by surface nitrates is a possibility. Titania catalysts supported on silicates have also been reported. These have higher PO selectivities at high conversion than silver catalysts.
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