Poisoning Effects of Chlorine on V2O5–WO3/TiO2 Catalysts for Selective Catalytic Reduction of NOx by NH3.

Chlorine species, widely presented in industrial flue gas such as the waste incineration plants, can poison the catalysts and affect the selective catalytic reduction (SCR) performance. In this work, effects of Cl on the SCR performance of V2O5–WO3/TiO2 (VW/Ti) catalysts were investigated by NH4Cl deposition. The results showed that the NOx conversion efficiency at low reaction temperature (< 300 °C) decreased with the loading of NH4Cl after calcination. It was found that instead of causing the chlorination of VW/Ti catalyst the NH4Cl decomposed into volatile Cl species due to the weak V–Cl bonding. Such decomposition reduced significantly the surface non-lattice oxygen species to inhibit NO adsorption and activation, but hardly affected the redox ability and acidity of VW/Ti catalyst. Time–resolved in situ DRIFTs results indicated that NH3 activation and the SCR process predominated by Eley–Rideal mechanism were not influenced with NH4Cl impregnation, while the SCR at low temperature following a Langmuir–Hinshelwood path was limited by the decreased and weaker binding sites for NO activation. [ABSTRACT FROM AUTHOR]