Poisoning mechanism of KCl, K₂O and SO₂ on Mn-Ce/CuX catalyst for low-temperature SCR of NO with NH₃

In this study, a series of K species or/and SO₂ poisoned Mn-Ce doped CuX (MCCX) catalysts were prepared from waste blast furnace slag (BFS), and the influence mechanism of K species or/and SO₂ poisoning on the catalysts in low-temperature NH₃-SCR process was investigated. The results demonstrated that MCCX-KCl catalyst had poorer NO conversion than MCCX-K₂O below 200 °C, and the co-existence of K species and SO₂ considerably inhibited NO conversion. Aggregation of the Cu active component might also be facilitated by co-poisoning with K species and SO₂. Furthermore, K species and SO₂ co-poisoned catalysts showed fewer isolated Cu²⁺ species and Mn⁴⁺ species than that of K-poisoned catalysts, indicating a decrease in active sites after the addition of SO₂. The co-effect of K₂O/KCl and SO₂ species impaired the redox capacity and decreased the surface acidity than K-poisoned catalysts to a greater extent. Nevertheless, K-poisoning had little effect on the surface intermediates during SCR reaction process, and K-poisoned catalysts followed both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanism. However, MCCX-KCl-SO₂ and MCCX-K₂O-SO₂ catalysts contained fewer nitrate species, indicating that the co-effect of K species and SO₂ impeded the reaction between NO + O₂ species and pre-NH₃ species, thereby resulting in poor low-temperature NH₃-SCR activity.