The stoichiometric oxidation of ethylene by anion radicals of cc-oxygen, (FeIII-O center dot-)(alpha), created on the surface of non-modified and Na-modified FeZSM-5 zeolite was studied in the temperature range from 25 down to -60 degrees C. Upon extraction, the products were identified using the gas chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance. Unlike the oxidation of methane, the reaction C2H4 + O-alpha was shown to proceed without hydrogen abstraction from the ethylene (infrared spectroscopy data). It leads to O-alpha addition over the double C=C bond yielding the ethylene oxide (EO) primary product. Sodium modification of the zeolite strongly increases the selectivity for EO, which attains 80-84% at the reaction temperature of -60 degrees C. A much lower selectivity at room temperature relates mainly to a secondary reaction of EO with ethylene leading to butyraldehyde. High epoxidizing selectivity of alpha-oxygen is discussed in relation to the mechanism of ethylene epoxidation on silver catalyst. (C) 2013 Elsevier Inc. All rights reserved,