Performance of membranes based on novel Ce0.8Sm0.2O2-δ /Ag cermet and molten carbonates for CO2 and O2 separation

Abstract

• SDC-Ag cermets exhibit outstanding wettability against molten carbonates. • Cermet shows metallic-like electrical conductivity; therefore, σ cermet ≫σ MC. • The cermet phase shows no degradation induced by molten carbonates. • Simultaneous CO 2 and O 2 separation are achieved for the long-term test. This work proposes a cermet infiltrated with a mixture of Li 2 CO 3 /Na 2 CO 3 /K 2 CO 3 as a dense membrane to selectively separate CO 2 and O 2 at high temperatures. The cermet consisted of a mixture of the Ce 0.8 Sm 0.2 O 2-δ (SDC) ceramic and silver as the metallic phase. This type of membrane is a novel design of the ceramic/carbonates type and represents an improvement of state-of-art designs by avoiding microstructural changes in the metallic phase and improving chemical inertness and wettability with the carbonate phase. First, an SDC nanostructured powder was chemically synthesized by direct combustion of urea: lanthanide nitrates-based deep eutectic solvent; then, SDC and silver powders were mixed in a 50:50 vol% ratio by using high energy ball milling. The mixture was uniaxially pressed and sintered to form a support. This cermet exhibited excellent wettability properties against the ternary molten carbonate phase; therefore, it readily allowed infiltration of the molten salts to form a dense membrane. Hence, the cermet showed excellent electronic conductivity as well as corrosion resistance in contact with carbonates for 200 h of continuous immersion. The cermet-carbonate membrane showed permselectivity by separating CO 2 and O 2 at high temperatures. It reaches simultaneous permeation values of 0.49 and 0.26 ml·min −1 ·cm −2 , for CO 2 and O 2, respectively, at 850 °C. Finally, continuous permeation tests at 825 °C for 85 h proved the excellent chemical stability of the cermet-carbonate membrane. Any chemical reactivity was not observed between the cermet and the carbonates.