Oxidation of C 2–C 4 hydrocarbons over MoO 3 and V 2O 5 supported on a YSZ-aided membrane reactor

Abstract

An electrochemical reactor, using yttria-stabilized zirconia (YSZ) as a solid electrolyte and gold and silver as the anode and cathode, respectively, has been employed for the selective partial oxidation of C 2–C 4 hydrocarbons at 775 K. MoO 3 or V 2O 5 was deposited as the catalyst film on the Au anode of the electrochemical cell. The reaction was carried out over the catalyst film under oxygen pumping through the cell; the results are compared with those obtained by the reaction with gaseous oxygen. Under oxygen pumping, no alkane was oxidized over MoO 3, while isobutane and propane were partially oxidized to methacrolein and propene, respectively, and ethane was oxidized a little over V 2O 5. It is supposed that CH cleavage is the rate determining step of the alkane oxidation over V 2O 5. Alkenes were partially oxidized over both MoO 3 and V 2O 5, and the selectivities to the oxygenated products, i.e., acetaldehyde, acrolein and methacrolein from ethene, propene, and isobutene, respectively, were higher on the former than on the latter. Over both MoO 3 and V 2O 5, the selectivity to aldehyde was higher in the reaction under oxygen pumping than in that by gaseous oxygen. Over MoO 3, the other oxygenated compounds than aldehyde were observed in the reaction by gaseous oxygen, while this is not the case under oxygen pumping. Under oxygen pumping, the highest selectivity was observed with methacrolein, followed by acrolein and acetaldehyde, among which acetaldehyde was further oxidized to carbon oxides. Over V 2O 5, alkenes were far more rapidly oxidized by gaseous oxygen than under oxygen pumping, and the selectivity to the oxygenated products were still higher under oxygen pumping than by gaseous oxygen. The highest selectivity was observed with methacrolein, and those of both acrolein and acetaldehyde were low. No further oxidation of acetaldehyde was observed over V 2O 5.