Partial oxidation of ethane by reductively activated oxygen over iron phosphate catalyst

The catalytic oxidation of ethane was carried out at 573-773 K over iron phosphate catalyst. The oxidation of ethane by oxygen produced only ethylene and carbon oxides. The co-feed of hydrogen with oxygen remarkably accelerated the conversion of ethane. Ethanol and acetaldehyde were newly formed by co-feeding hydrogen. The partial oxidation of ethane to ethanol and acetaldehyde can also be achieved by using nitrous oxide as an oxidant. The co-feed of hydrogen with nitrous oxide increased the conversion of ethane and the yield to C-2 oxygenates. The investigation on the reaction paths suggests that ethanol is the primary product in the oxidation of ethane with hydrogen-oxygen gas mixture and with nitrous oxide. Acetaldehyde and ethylene are produced through further oxidation and dehydration of ethanol, respectively. The highest yield obtained for C-2 oxygenates was 4.4% (ethanol, 1.4%; acetaldehyde, 3.0%) at 673 K. The kinetic and mechanistic studies suggest that the oxidation of ethane proceeds by a similar reaction mechanism to the one proposed for the oxidation of methane. Oxygen is activated by the electrons and protons derived from hydrogen on the catalyst surface, generating a new oxygen species, probably adsorbed peroxide species, effective for the selective oxidation of ethane to ethanol. The same oxygen species can be generated from nitrous oxide by its reductive activation. Both kinetic results and isotopic effects on the conversion of ethane suggest that the dissociation of the C-H bond of ethane proceeds notably faster than the formation of the active oxygen species. In contrast with ethane, the rate of activation of methane was comparable to that of the generation of the active oxygen species. (C) 1997 Academic Press.