Oxidation of ethane over vanadia-alumina-based catalysts: co-feed and redox experiments

The conversion of ethane in mixture with oxygen and helium (or air) over a V2O5/Al2O3 12:88 (w/w). and a V2O5-K2O/Al2O3 12:6:82 (w/w) catalysts has been studied. Results of co-feed experiments (with ethane-oxygen-He and with ethane-air feeds) and redox experiments, performed feeding pure ethane over fully oxidized catalysts, have been compared. Data concerning propane conversion over the same catalysts have also been considered. Over the heavily K-doped sample a direct combustion way to CO2 parallel to the oxydehydrogenation way to ethylene is likely to exist. On the contrary, over undoped vanadia-alumina the main combustion way is successive and mainly gives CO. Similar yields have been obtained but at lower temperatures for co-feed than for redox experiments. However, in similar conditions the productivities can be definitely higher in redox than in co-feed experiments. Nevertheless the conversion of ethane in the empty reactor gives rise to definitely higher selectivities and yields, although at very high temperatures, than the catalyzed reactions. (C) 2002 Elsevier Science B.V. All rights reserved.