Effect of preparation methods on the performance of MnOx-TiO2 adsorbents for Hg0 removal and SO2 resistance

Aiming at the difficulty of elemental mercury (Hg0) removal from flue gas due to its indissolubility in water and the problem of lower SO2 resistance performance of manganese-based adsorbent, the MnOx-TiO2 adsorbents prepared with impregnation (IM), sol-gel (SG) and deposition-precipitation method (DP) were employed to remove Hg0 in the absence and presence of SO2. The adsorbents were characterized by N2 adsorption-desorption, TG-DSC, XRD, TEM, H2-TPR, and XPS techniques. The results showed that Hg0 removal performance over MnOx-TiO2 adsorbents was markedly influenced by the preparation methods. The adsorbent prepared by DP method exhibited a superior activity for Hg0 adsorption and the best SO2 resistance performance. The characterization results indicated that the Hg0 removal activity did not correlate with the BET surface area. The preparation method of deposition-precipitation could not only lead to an increase of reducibility and high dispersion of MnOx, but also significantly enhance a migration of well-dispersed active phase from bulk to surface, resulting in a higher Mn4+/Mn ratio and the presence of abundant chemisorbed oxygen, which would play an important role in promoting Hg0 removal.