Absorption/desorption of NOx process on perovskites: impact of SO2 on the storage capacity of BaSnO3 and strategy to develop thioresistance

The formation of species when BaSnO3 is exposed to SO2 under a variety of conditions is reported and discussed. Direct contact with 25 ppm SO2 during 15 cycles of Lean–Burn operation leads to the complete loss of NOx absorption capacity owing to the formation of stable and irreversible bulk-like sulphates identified by FT-IR (990, 1060, 1125 and 1190 cm−1) and TGA–MS. When both NO2 and SO2 are present, the competition between the formation of nitrate and sulphate favours the latter, leading eventually to deactivation. If the catalyst is pre-nitrated before exposure to SO2, the co-existence of nitrates and sulphates between 100 and 300°C is possible and improved sulphur tolerance is obtained.