A kinetic and surface study of the oxidation of ethane by nitrous oxide and by oxygen over manganese(III) oxide

Article abstract of DOI:10.1139/v82-133

The kinetics of the nitrous oxide/ethane and oxygen/ethane reactions on manganese(III) oxide have been studied from 573 to 673 K and from 523 to 593 K, respectively.The apparent activation energy for carbon dioxide formation was 130+/-4kJ mol^-1 in both reactions while that for nitrogen formation in the nitrous oxide/ethane reaction changed from 106+/-4 kJ mol^-1, 573-613 K, to 133+/-4 kJ mol^-1, 623-673 K.The kinetic results for both reactions fit the same rate equation: (formula) where p_x represents either p_N2O or p_O2.The rate-controlling step has been associated with the interaction of absorbed species on the catalyst surface while both ethane and oxidising gas appear to be directly involved in further steps in the mechanism.Samples were analysed routinely by scanning electron microscopy, X-ray powder diffraction, and infrared spectroscopy.Electron spectroscopy results from samples treated in various ways with hydrocarbon/oxidant mixtures gave O(1s) values from 528.7 to 529.7 eV which are indicative of binding energies usually associated with chemisorbed oxygen.No N(1s) spectrum was obtained from catalysts exposed to hydrocarbon/nitrous oxide mixtures, in agreement with the absence of bands in the infrared which are usually associated with nitrates or nitrogen/oxygen complexes.A binding energy value of 406.5 eV was measured in the comparable N(1s) spectrum of a catalyst used at 623 K for the oxydation of ethane by nitric oxide - a result which confirms conclusions from previous surface studies on the same system using infrared spectroscopy.