Effect of barium sulfate modification on the SO tolerance of VO/TiO catalyst for NH-SCR reaction.

Sulfur poisoning of VO/BaSO-TiO (VBT), VO/WO-TiO (VWT) and VO/BaSO-WO-TiO (VBWT) catalysts was performed in wet air at 350°C for 3hr, and activities for the selective catalytic reduction of NO with NH were evaluated for 200-500°C. The VBT catalyst showed higher NO 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.