Experimental study on the mercury removal from flue gas using manganese modified titanium-zirconium and titanium-tin composite oxide catalysts

In this study, TiO₂, TiZr and TiSn supports were prepared using co-precipitation method, and MnTi, MnTiZr, and MnTiSn catalysts with MnO₂ content of 10%were prepared by the wet impregnation method. BET, XRD, H₂-TPR, FT-IR, and XPS were employed to characterize the prepared samples. The Hg⁰ removal performance tests over the three catalysts were conducted in a fixed-bed reactor apparatus. The results indicated that the Hg⁰ removal performance of MnTiZr and MnTiSn catalysts was better than that of MnTi catalyst in the temperature range of 100-300℃. This could be attributed to the introduction of Sn and Zr, which increased the specific surface area of the catalyst, improved the low-temperature redox performance of the catalyst, and elevate the number of acid sites, the high valence manganese ions concentration and O^* content on the catalyst surface. The mercury removal efficiency of the MnTiSn catalyst was higher than that of MnTiZr catalyst at reaction temperature of 150-300℃, which could be ascribed to the higher redox performance of the MnTiSn catalyst and more content of the high valence manganese ions, O^*, and surface acid sites on its surface. During the removal of Hg⁰ in flue gas by MnTiZr and MnTiSn catalysts, active ingredients on the catalyst surface such as high-valence manganese ions and O^* were consumed and participated in the reaction of Hg⁰ oxidation to Hg²⁺. And the consumed amount of active ingredients on the surface of MnTiSn catalyst was more than that on the MnTiZr catalyst.