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'Atmospheric' direct route to propylene oxide
A significant research problem in industrial chemistry has been to find a direct oxidation process to make propylene oxide, a versatile chemical intermediate. In theory, combining O2 with propylene should work, but the conversion is low. So instead, a pair of two-step processes currently are used to manufacture propylene oxide--the chlorohydrin process and the peroxidation process--but both have major coproducts. Now, Torsten Berndt of the Institute for Tropospheric Research in Leipzig, Germany, and coworkers have uncovered a potentially viable direct route to propylene oxide by reacting propylene with nitrogen(V) oxides such as nitrate radicals in the gas phase--chemistry the researchers observed while conducting atmospheric studies [Ind. Eng. Chem. Res., 42, 2870 (2003)]. The researchers combine NO2 with O3 and add the mixture to propylene in a flow-through gas reactor. The nitrogen(V) oxides formed act as an oxygen-transfer agent to convert propylene to propylene oxide with yields and selectivity comparable with the current industrial routes, Berndt notes. This noncatalytic nitrate oxidation route would be a lucrative alternative if it can be successfully scaled up, the researchers believe.
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