Getting Insights into the Synergistic Effects of Zn and HCl on the SCR Performance of the CeO ₂ –TiO ₂ Catalyst

This study investigates the effects of Zn or HCl on the selective catalytic reduction (SCR) performance of a CeO2–TiO2 catalyst. The fresh catalyst exhibited superior activity, achieving >90% NOx conversion from 200 to 450 °C. The introduction of Zn or HCl resulted in varying degrees of catalytic inhibition. At 200 °C, NOx conversion decreased by ∼12 or ∼47% for the HCl- or Zn-poisoned sample, respectively. The reductions in specific surface area, surface acidity, oxidizing capability, and NOx adsorption capacity contributed to the observed deactivation of the catalysts. Notably, the catalyst co-poisoned with Zn&HCl showed a recovery in SCR activity compared with the Zn-only poisoned sample, with NOx conversion at 250 °C increasing from about 86% to nearly 100%. This offsetting effect might be ascribed to the partial restoration of specific surface area, acid sites, Ce3+ concentration, and chemisorbed oxygen content under the action of HCl. This result could offer valuable insights into the practical application of the CeO2–TiO2 catalyst under real coal-fired flue gas conditions.