Influence of flue gas components on the chemical properties of the ceramic materials (Co-)Ce0,8Gd0,2-xPrxO2-δ

Materials in the system (Co-)Ce0.8Gd0.2-xPrxO2-δ are often used materials in the catalyst technology due to its oxygen storage capacity and are promising candidates for mixed conductive layer on membranes for oxygen separation in the Oxyfuel process. In both cases the material is exposed temperatures around 800 deg. C and is in contact with aggressive gas species like CO2 and SO2, which may react with the ceramic material leading to a drop in their functional properties. In this work ceramic powder species with x = 0; 0.01; 0.03; 0.05; 0.1 and 0.2 were tested in two gas mixtures containing 99 vol.% CO2 and 1 vol.% SO2 on the one hand and 96.3 vol.% CO2, 3.6 vol.% O2 and 0.1 vol.% SO2 on the other hand. The ceramic powders were treated for 5 hours at 800 deg. C. Before and after the treatment a phase analysis was done by XRD. X-ray amorphous sulphates and the belonging cations were quantified by a wet chemical route. Under CO2 gas the ceramic powders show a good chemical stability. The gassing with SO2 containing test gases causes a chemical expansion of the lattice in dependence of Pr content x due to a release of oxygen. Also small amounts of sulphate were found in the gassed samples. A small content of oxygen in the test gas (3.6 vol.-%) reduces the chemical expansion and the sulphate formation during the test significantly. An additional doping with 2 wt.-% Co inhibits the sulphate formation entirely.