Activated carbon loaded MnOx catalyst prepared by ultrasound-assisted impregnation method-promising for the flue gas desulfurization in coking industry

A novel flue gas purification system was proposed for the coking industry with the catalytic oxidation method identified as a favorable desulfurization method. A series of MnOx/AC desulfurization catalysts were synthesized using the ultrasound-assisted excessive impregnation method and the SO₂ removal efficiency of catalysts was evaluated at the reaction temperature of 150 °C. The influence of the precursor, calcination temperature, and loading ratio on desulfurization performance was studied. The characterization technologies including N₂ adsorption/desorption, SEM, XRD, XPS, TPR, and FT-IR were employed to analyzing the physicochemical characteristics of catalysts. The results indicated that the doping of Mn can significantly improve the desulfurization activity of catalysts. The catalysts synthesized by manganese nitrate exhibited better desulfurization activity, which is contributed to the highly dispersed surface Mn oxides from the decomposition of manganese nitrate. The orderly crystalline structures and abundant oxygen-containing groups from surface Mn oxides enhanced the desulfurization activity. Meanwhile, a calcination temperature of 800℃ facilitated the formation of Mn₃O₄ species, which can easily provide lattice oxygen for SO₂ oxidation process. Furthermore, a 10% loading ratio was found to be a suitable loading for the catalysts, corresponding to the monolayer dispersion capacity of the applied activated carbon.