The inhibition effect and deactivation mechanism of H2O and SO2 on selective catalytic oxidation of NO over the Mn–Ca–Ox–(CO3)y catalyst

Abstract

The Mn–Ca–O_x–(CO₃)_y catalyst was used in this work for selective catalytic oxidation of NO. The influences of SO₂, H₂O and H₂O + SO₂ on the deactivation process were investigated. Surface morphology and pore structure analyses indicated that SO₂ reacted with the catalyst to form larger particles and H₂O could react with MnCO₃ to form smaller particles. The XRD results showed that the deactivation product under SO₂ atmospheric conditions was MnSO₄. The XPS results showed that H₂O could promote the formation of MnO₂. The H₂-TPR results indicated that the influence of H₂O on oxidation activity sites was weak. Meanwhile, the introduction of SO₂ increased the activation temperature. The DRTFIR experimental results indicated that SO₂ had a direct chemical interaction with the catalyst and the formation of MnSO₄ does not rely on O₂. O₂ enhanced the chemical interaction between SO₂ and the catalyst. SO₂ adsorbed on the catalyst surface prior to NO. The SO₂ deactivation process was irreversible and it was attributed to chemical deactivation. H₂O inhibited the transformation from nitro to NO₂ and the H₂O deactivation process was attributed to physical deactivation.