PARTIAL OXIDATION OF C-2-C-4 ALKANES INTO OXYGENATES USING AN AU-VERTICAL-BAR-YTTRIA-STABILIZED ZIRCONIA-VERTICAL-BAR-AG ELECTROCHEMICAL REACTION CELL

An electrochemical reactor, using yttria-stabilized zirconia (YSZ) as a solid electrolyte, and gold and silver as the anode and cathode, res pectively, has been employed for the selective partial oxidation of al kanes at 425-475 degrees C. Using this system, ethane was converted to acetaldehyde, propane to acetone and acrylaldehyde, butane to methyl ethyl ketone and methyl vinyl ketone, and isobutane to methacrolein. I n all cases the combustion products, carbon dioxide and carbon monoxid e, were also formed. Alkane oxidation only occurred when the electrica l circuit was closed and a current applied across the electrodes; the production rate of the oxygenated products increased as the current, a nd therefore the oxygen flux across YSZ, was increased. In the presenc e of only gas-phase dioxygen, oxidation gave carbon oxides. Therefore, it is the electrochemically generated oxygen species that is responsi ble for the formation of oxygenates from alkanes. It is suggested that the active oxygen species is generated from the 'pumped' oxide ions a ppearing at the gold/YSZ/gas-phase three-phase boundary. The oxidation of butene to methyl vinyl ketone and crotonaldehyde, and isobutene to methacrolein (and some isobutylene oxide) is also demonstrated.