Effect of Different Zinc Species on Mn-Ce/CuX Catalyst for Low-Temperature NH₃-SCR Reaction: Comparison of ZnCl₂, Zn(NO₃)₂, ZnSO₄ and ZnCO₃

The effects of four distinct zinc species (ZnCl₂, Zn(NO₃)₂, ZnSO₄, and ZnCO₃) on a Mn-Ce co-doped CuX (MCCX)catalyst were investigated and contrasted in the low-temperature NH₃-SCR process. Aqueous solutions of ZnCl₂, Zn(NO₃)₂, ZnSO₄, and ZnCO₃ were used to poison the catalysts. The catalytic activity of all catalysts was assessed, and their physicochemical properties were studied. There was a notable drop trend in catalytic activity in the low temperature range (200 °C) after zinc species poisoning on MCCX catalyst. Interestingly, ZnSO₄ and ZnCO₃ on MCCX catalyst had more serious effect on catalytic activity than Zn(NO₃)₂ and ZnCl₂ from 150 °C to 225 °C, in which NO conversion of the MCCX-Zn-S and MCCX-Zn-C catalysts dropped about 20–30% below 200 °C compared with the fresh MCCX catalyst. The zeolite X structure was impacted by Zn species doping on the MCCX catalyst, and the Zn-poisoned catalysts had less acidic and lower redox ability than fresh Mn-Ce/CuX catalysts. Through the results of in situ DRIFTS spectroscopy experiments, all catalysts were governed by both Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms, and the possible mechanism for poisoning the Mn-Ce/CuX catalyst using various zinc species was revealed.