Effect of barium sulfate modification on the SO2 tolerance of V2O5/TiO2 catalyst for NH3-SCR reaction.

Sulfur poisoning of V2O5/BaSO4-TiO2 (VBT), V2O5/WO3-TiO2 (VWT) and V2O5/BaSO4-WO3-TiO2 (VBWT) catalysts was performed in wet air at 350°C for 3hr, and activities for the selective catalytic reduction of NOx with NH3 were evaluated for 200-500°C. The VBT catalyst showed higher NOx conversions after sulfur poisoning than the other two catalysts. The introduction of barium sulfate contributed to strong acid sites for the as-received catalyst, and eliminated the redox cycle of active vanadium oxide to some extent, which resulted in a certain loss of activity. Readily decomposable sulfate species formed on VBT-S instead of inactive sulfates on VWT-S. These decomposable sulfates increased the number of strong acid sites significantly. Some sulfate species escaped during catalyst preparation and barium sulfate was reproduced during sulfur poisoning, which protects vanadia from sulfur oxide attachment to a great extent. Consequently, the VBT catalyst exhibited the best resistance to sulfur poisoning.