Oxidative coupling of CH4 using alkali-metal ion conductors as a solid electrolyte

Abstract

The oxidative coupling of CH₄ to C₂H₄ and C₂H₆(C₂-hydrocarbons) has been carried out using an Li⁺ ion conductor as a solid electrolyte. A single-compartment cell is constructed from (Li₂O)_0.17(BaO)_0.07(TiO₂)_0.76(LBT) ceramic with two gold electrodes. Alternative current voltages are applied between the two electrodes with a mixture of 8.3% CH₄ and 1.6% O₂ in argon. The experiments are carried out under various conditions. The formation of C₂-hydrocarbons is the most effectively enhanced at a temperature of 850 °C or a frequency of 10 Hz. For example, the conversion of CH₄ and the selectivity of C₂-hydrocarbons at 3 V are 2 and 1.5 times more than those at the open circuit, respectively. The applications of a dc voltage to a two-compartment cell suggested that the active sites are generated via the cathodic reaction. The mechanism for the formation of C₂-hydrocarbons is discussed in detail.