Catalyst-modified perovskite hollow fiber membrane for oxidative coupling of methane

Abstract

The catalytic oxidative coupling of methane (OCM) to C2 hydrocarbons (C2H6 and C2H4) represents one of the most effective ways to convert natural gas to more useful products, which can be performed effectively using La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) perovskite hollow fiber membrane microreactor. In this work, the effects of adding a thin BaCe0.8Gd0.2O3−δ (BCG) catalyst film onto the inner LSCF fiber surface as the OCM catalyst and a porous Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) perovskite layer onto the outer LSCF surface to improve the oxygen permeation were evaluated. Between 700 °C and 1000 °C, methane conversion increased in the order of uncoated, BCG and BSCF-coated, and BCG-coated LSCF hollow fiber while C2-selectivity and C2-yield increased in the order of BCG and BSCF-coated, uncoated, and BCG-coated LSCF hollow fiber. Oxygen permeation flux at the same temperature range, on the other hand, was enhanced in the order of uncoated, BCG-coated, and BCG and BSCF-coated LSCF hollow fiber. This finding demonstrates the complex interplay between oxygen permeation and OCM performance. The BCG and BSCF-coated hollow fiber was also subjected to thermal cycles between 850 °C and 900 °C for up to 175 hours during which the fiber showed minor degradation in oxygen permeation fluxes and relatively stable OCM performance.