The effect of SO2 on the structural evolution of a supported Mn2V2O7 catalyst and its DeNOx performance

Abstract

To investigate the structural evolution of vanadate catalysts in the presence of SO₂ and its influence on DeNO_x behaviors, three typical vanadate catalysts (unsupported Mn₂V₂O₇, Mn₂V₂O₇/TiO₂, and sulphated Mn₂V₂O₇/TiO₂) were designed for the selective catalytic reduction of NO with NH₃. The XRD, Raman, and S 2p XPS spectra and TG results confirmed the SO₂-promoted decomposition of supported Mn₂V₂O₇ to form VO_x species and MnSO₄ on TiO₂. The XPS spectra of V 2p and (HR)TEM images further indicated the fusion of the decomposed VO_x with TiO₂ with increased dispersity for the active V species. The decomposition and sulfation of supported Mn₂V₂O₇ markedly increased the specific surface area with the exposure of more active Mn/V sites, O_α species and acid sites as demonstrated by the XPS spectra of O 2p and BET, NH₃-TPD and H₂-TPR results. The catalytic test exhibited that the formation of MnSO₄ devitalized the Mn-based low-temperature active sites and worsened the low-temperature DeNO_x performance below 250 °C, but the decomposition and sulfation of the supported Mn₂V₂O₇ significantly enhanced the catalytic activity and N₂ selectivity above 250 °C owing to the exposure of more active V sites, O_α species and acid sites. These research results imply that the vanadate catalysts may be unstable in the presence of SO₂ and more suitable for the purification of sulfur-free or pre-desulfurization flue gases in the high temperature range.