Superior PbO-resistance of CeO₂/ZrO₂ catalyst promoted by solid superacid SO₄²⁻/ZrO₂ for selective catalytic reduction of NO_x with NH₃

The serious deactivation of denitration catalysts caused by heavy metals still a thorny issue in the practical application of selective catalytic reduction of NO_x with NH₃. Herein, we proposed a novel anti-poisoning strategy by designing SO₄²⁻/ZrO₂ superacid supported CeO₂/ZrO₂ catalyst, and the effect of SO₄²⁻/ZrO₂ supported CeO₂/ZrO₂ for PbO-resistance NO_x catalytic reduction was investigated. It was worthy to note that the introduction of solid superacid SO₄²⁻/ZrO₂ significantly enhanced catalytic performance over the entire temperature range, with an exceptionally high NO_x removal efficiency over 98 % during 250–500 °C. When 2 wt% PbO was deposited on the fresh catalyst, the catalytic activity of CeO₂/ZrO₂ catalyst decreased obviously, while CeO₂/ZrO₂-S catalyst can still maintain a higher NO_x conversion over 90 % from 275 to 500 °C. The characterization results confirmed that the introduction of solid superacid SO₄²⁻/ZrO₂ enhanced the surface acidity and promoted the transformation from Ce⁴⁺ to Ce³⁺. The results of in situ DRIFTS implied that the Eley-Rideal (E-R) mechanism was obeyed over CeO₂/ZrO₂ catalyst, and both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms were followed over CeO₂/ZrO₂-S catalyst in the SCR process. With regard to poisoned catalysts, the NH₃ adsorption was inhibited to some extent, while the reaction mechanism wasn't changed by PbO poisoning.