Membrane reactor for oxidative coupling of CH4with an oxide ion–electron hole mixed conductor

Abstract

A membrane reactor for the oxidative coupling of CH4 has been constructed with an oxide ion–electron hole mixed conductor, BaCe0.8Gd0.2O3–α. 10% CH4 diluted with Ar and an O2–Ar mixture at a given ratio were fed into opposite sides of the membrane at 1173 K. The formation rate of C2–hydrocarbons (ethane and especially ethene) in the CH4 compartment increased with Po2 in the O2–Ar compartment. This enhancement was due to electrochemical oxygen permeation, causing the conductor to short-circuit itself, resulting form the mixed conduction. For comparison, 10% CH4 and a small amount of O2 were co-fed into one side of the membrane. The membrane operation gave a C2 selectivity two times that of the co-feed operation for all CH4 conversions. From a catalytic study using BaCe1–xGdxO3 –α powders as catalyst, it was found that increasing both the oxide-ion and electron-hole conductivities enhanced the formation of C2 hydrocarbons, but reduced that of CO2. On the basis of these results, a mechanism for the oxidative coupling of CH4 of the mixed-conductor membrane was proposed.