Long-term stability of iron-doped calcium titanate CaTi0.9Fe0.1O3−δ oxygen transport membranes under non-reactive and reactive atmospheres

Abstract

Oxygen transport membranes (OTM) are widely considered as a possible solution to limit the carbon footprint, but are notoriously afflicted by performance issues due to chemical instability observed during long-term operation. This paper reports on the stability of an OTM made of CaTi0.9Fe0.1O3−δ (CTF), and addresses its applicability. The redox stability of CTF was investigated using thermal gravimetry up to 1000 °C under air and H2, coupled with XRD and Mössbauer analyses. The redox potential of iron was measured using an electrochemical potential relaxation as a function of temperature. The baseline oxygen semi-permeability flux of dense CTF membranes was measured in inert atmospheres (air/argon or air/helium), and the long-term stability established for up to 1600 h under simulated operation atmospheres containing CO, CO2, H2 and CH4. CTF shows a remarkable performance stability and post mortem XRD, SEM-EDS and Raman analyses show no evidence of decomposition or reaction byproducts.