(138a) Highly Efficient SO2 Removal By Supported Manganese Sorbents for SOFCs Cathode Protection

Because of high energy efficiency and fuel flexibility, Solid Oxide Fuel Cells (SOFCs) are promising energy converting devices nowadays. However, researchers realized that SO₂ can cause a rapid degradation by interacting with cathode side materials. In logistic solid oxide fuel cell systems, the sources of SO₂ mainly arise from high sulfur-containing marine fuels, such as JP-5 and JP-8. Therefore, the cathode protection for SOFCs is a vital consideration for the power system. In this study, dispersed manganese oxides on supports such as ZrO₂, SiO₂, γ-Al₂O₃, and TiO₂ were prepared by a method of incipient wetness impregnation (IWI). The breakthrough performance was evaluated in a conventional fixed-bed sorption system. Effects of precursor materials, supports, manganese loadings, and calcination temperature on the sorbent performance were investigated in details. A combination of various surface science techniques, including XRD, N₂ physisorption, O₂ chemisorption, H₂-TPR, and XPS, were applied to characterize the chemical environment of the adsorbents. The highest saturation capacity was obtained by using 5 wt.% Mn supported on ZrO₂. XRD and O₂ chemisorption results demonstrated that MnO₂ and Mn₂O₃ co-existed in well-dispersed forms at 5.0 wt.% of Mn on ZrO₂. It was also found that the amount of manganese in sorbent has a remarkable influence on the oxidation state of manganese. In addition, XPS results revealed that the performance of Mn-doped adsorbent was strongly dependent on the population of surface terminal hydroxyl groups.