Mixed Ionic/Electronic Conducting Ceramic Membranes for Oxygen-Assisted CO2 Reforming

Abstract

Incorporating a SrFeCo0.5Ox (SFC) membrane into a CO2 reforming reactor doubles methane conversion with a powder Pt/ZrO2 catalyst. The deactivation of both Pt/ZrO2 and a Pt/CeZrO2 catalyst is also retarded substantially. Catalyst performance improvement is attributed to a beneficial in situ effect of the SFC membrane on catalyst oxidation state. The SFC membranes exhibit low oxygen flux (< 0.01 sccm/cm^2) and insignificant methane conversion activity. The molecular-level effects of SFC membranes, co-fed gas-phase oxygen, and conventional powder catalyst oxidation state are all assessed using reactor effluent composition trends. A novel single parameter (the Oxidation Factor) is proposed for evaluating product selectivity for CO2 reforming in the presence of oxygen. Membrane oxygen release is attributed entirely to hydrogen oxidation on the membrane surface under these reforming reaction conditions. This claim contradicts a long-standing assumption in the literature that membrane oxygen participates in reforming reactions as molecular oxygen.