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 NO_x 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.