H2S poisoning and regeneration of Ni-BaZr0.1Ce0.7Y0.2O3-δ at intermediate temperature

Hydrogen permeation flux of Ni-BaZr0.1Ce0.7Y0.2O3-delta cermet (ceramic-metal composite) was measured in an H2S-containing atmosphere at 973 K. In 30 and 60 ppm, H2S, the hydrogen permeation flux decreased by about 20% and 30%, respectively. After the removal of H2S, the hydrogen permeation flux recovered partially in several hours and then remained stable. After exposing to 60 ppm H2S, X-ray diffraction (XRD) analysis revealed a little formation of Ni3S2, BaS, and doped CeO2. Thermodynamic calculation results showed that the critical value of pH(2)S/pH(2) for the formation of Ni3S2 was about 0.0066 at 973 K, suggesting that the Ni3S2 found after testing was formed in the cooling process. The reaction between H2S and BaCeO3 was rather weak and could not be the cause of the performance loss. Analysis of poisoning and regeneration behavior suggested that the adsorption of sulfur on nickel surface caused the performance loss. (C) 2008 Elsevier B.V. All rights reserved.