Supported manganese dioxide catalyst for seawater flue gas desulfurization application

In seawater flue gas desulfurization (FGD) process, ceramic supported MnOx catalysts were developed to improve SO2 removal efficiency of the scrubber by increasing S(IV) oxidation rate at the low pH values. These supported MnOx catalysts were prepared by impregnation–precipitation method, calcined at different temperatures, and exposed to simulated flue gases to investigate the catalytic oxidation of sulfur dioxide in seawater buffering system. Compared with “blank” ceramic, the most active MnOx/ceramic catalyst, 623MnOx/ceramic, that was prepared by doping (NH4)2CO3 as the precipitant and calcined at 623 K, exhibited up to 17% higher SO2 conversion at the GHSV 3000 h−1 in the industrial feasible temperature range of 318–358 K. XPS spectra revealed manganese was in the state of oxidation +4 on the surface of 623MnOx/ceramic. XRD patterns and SEM-EDS spectra indicated that the high activity of 623MnOx/ceramic for S(IV) oxidation at low temperatures could be attributed to oxygen activation and transfer ability of highly dispersed MnO2 on ceramic support. H2-TPR profiles showed the low temperature reduction peak was shifted to higher temperature when the calcination temperature increased from 573 K to 723 K, and low temperature reducible manganese species were related to catalytic activity for S (IV) oxidation. The good performance of MnO2/ceramic catalyst on the SO2 removal appeared to be promising in seawater FGD application when high sulfur coals were burned.

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► Active MnOx/ceramic catalysts were prepared by impregnation–precipitation for seawater FGD.
► MnOx was highly dispersed on ceramic with oxidation state +4 for the sample calcined at 623 K.
► Oxygen activation and transfer ability of MnOx/ceramic was related to its catalytic activity of S(IV) oxidation.
► MnOx/ceramic catalysts exhibited up to 17% higher desulfurization efficiency at GHSV 3000 h−1.