SELECTIVE OXIDATION OF ETHANE USING THE AU-VERTICAL-BAR-YSZ-VERTICAL-BAR-AG ELECTROCHEMICAL MEMBRANE SYSTEM

The catalytic conversion of ethane to acetaldehyde on an inert gold el ectrode has been studied using the electrochemical membrane reactor wi th yttria-stabilized zirconia (YSZ) solid electrolyte at 475 degrees C . On applying a direct current to the reaction cell, 5% ethane in N-2, Au\YSZ\Ag, 100% O-2, acetaldehyde was formed and the formation rate i ncreased linearly with increasing current. Selectivities to acetaldehy de and carbon dioxide were 45 and 55%, respectively. The addition of o xygen to the ethane-mixed gas in the anode space did not affect the ac etaldehyde formation. The use of YSZ powder as a fixed bed catalyst un der the mixed gas flow of ethane and oxygen at 450 to 600 degrees C re sulted in the formation of carbon monoxide, carbon dioxide, and ethene . Even the use of N2O instead of oxygen resulted in no formation of ac etaldehyde. Hence, it is likely that partial oxidation of ethane to ac etaldehyde was carried out by the oxygen species transferred electroch emically through the YSZ which appeared at the gold-YSZ-gas triple-pha se boundary. From the results of ethanol oxidation over the Au\YSZ\Ag system, the following mechanism was proposed: ethane is dehydrogenated to an ethyl radical, then converted to ethoxide, and finally to aceta ldehyde by the oxygen species transferred through the YSZ.