Theoretical Study of the Catalytic Activity and Anti-SO₂ Poisoning of a MoO₃/V₂O₅ Selective Catalytic Reduction Catalyst

In this paper, density functional theory has been applied to study the mechanism of anti-SO₂ poisoning and selective catalytic reduction (SCR) reaction on a MoO₃/V₂O₅ surface. According to the calculation results, the SO₂ molecule can be converted into SO₃ on V₂O₅(010) and further transformed into NH₄HSO₄, which poisons V₂O₅. If V₂O₅ and MoO₃ are combined with each other, charge separation of V₂O₅ and MoO₃, which are negatively and positively charged, respectively, occurs at the interface. In ammonium bisulfate liquid droplets on the MoO₃/V₂O₅ surface, NH₄ ⁺ tends to adhere to the V₂O₅(010) surface and can be removed through the SCR reaction and HSO₄ ^- tends to adhere to the MoO₃(100) surface and can be resolved into SO₃ and H₂O, which can be released into the gas phase. Thus, MoO₃/V₂O₅ materials are resistant to SO₂ poisoning. In the MoO₃/V₂O₅ material, Brønsted acid sites are easily formed on the negatively charged V₂O₅(010) surface; this reduces the energy barrier of the NH₃ dissociation step in the NH₃-SCR process and further improves the catalytic activity.