Investigation of Mg-doping effect on the activity and P tolerance of V₂O₅-MoO₃ /TiO₂ catalysts for NH₃-SCR

V₂O₅-MoO₃/TiO₂ catalyst modified by Mg was studied to obtain higher NOx SCR activity and higher P, SO₂, and H₂O resistance than the V₂O₅-MoO₃/TiO₂. The results show that Mg modification can promote the denitration activity of V₂O₅-MoO₃/TiO₂ catalyst, and the maximum NOx removal efficiency of Mg₁-SCR catalyst was 97.5%; the optimum reaction temperature and flow rate were 350℃ and 1200 mL/min, respectively. Mg doping can broaden the reaction temperature window of the catalyst, and the denitration efficiency can reach more than 87% at 300℃. P₂O₅ solution was prepared as poisoning precursor and mixed with catalyst to simulate the process of catalyst P-poisoning. The step-wise study showed that Mg_0.5-SCR and Mg₁-SCR catalyst displays higher durable resistance to P, SO₂, and H₂O than original catalyst. The degree of denitrification efficiency reduction of Mg₁-SCR is 4% smaller than that of Mg₀-SCR after passing SO₂. Mg_0.5-SCR catalyst achieves 88% denitrification efficiency at 350 °C after simulating phosphorus poisoning. The catalysts have been characterized by X-ray diffraction, Brunner - Emmet - Teller, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscop, programmed temperature desorption, and programmed temperature reduction. The obtained results suggested that the Mg doping made the active components more dispersed on the surface of the supports, improved the thermal stability of the catalyst, promoted the transition of VOx from monomeric state to polymerized state, inhibited the interaction between P and V, and protected the acid site.