Sulfur Dioxide Capture by Heterogeneous Oxidation on Hydroxylated Manganese Dioxide

Abstract

Here we demonstrate that sulfur dioxide (SO2) is efficiently captured via heterogeneous oxidation into sulfate on the surface of hydroxylated manganese dioxide (MnO2). Lab-scale activity tests in a fluidized bed reactor showed that the removal efficiency for a simulated flue gas containing 5000 mg·Nm(-3) SO2 could reach nearly 100% with a GHSV (gas hourly space velocity) of 10000 h(-1). The mechanism was investigated using a combination of experimental characterizations and theoretical calculations. It was found that formation of surface bound sulfate proceeds via association of SO2 with terminal hydroxyls. Both H2O and O2 are essential for the generation of reactive terminal hydroxyls, and the indirect role of O2 in heterogeneous SO2 oxidation at low temperature was also revealed. We propose that the high reactivity of terminal hydroxyls is attributed to the proper surface configuration of MnO2 to adsorb water with degenerate energies for associative and dissociative states, and maintain rapid proton dynamics. Viability analyses suggest that the desulfurization method that is based on such a direct oxidation reaction at the gas/solid interface represents a promising approach for SO2 capture.

Simultaneous Sulfite Electrolysis and Hydrogen Production Using Ni Foam-Based Three-Dimensional Electrodes

“…Studies focused only on SO 2 removal reported higher conversions. An ozonation method assisted by Mn 2+ achieved almost a 99% conversion, while gas/solid oxidation on MnO 2 reached nearly 100% . However, a fair comparison is difficult because configurations were not strictly the same.…”

“…An ozonation method assisted by Mn 2+ achieved almost a 99% conversion, 6 while gas/solid oxidation on MnO 2 reached nearly 100%. 55 However, a fair comparison is difficult because configurations were not strictly the same. Furthermore, some electrochemical systems with simultaneous SO 3 2− oxidation and H 2 production have been reported.…”

Progress of Catalytic Oxidation of Formaldehyde over Manganese Oxides

“…In some mechanisms, the DOM species are firstly produced, then converted to the formate intermediate, subsequently oxidized to carbonate, and finally decomposed to form CO 2 and H 2 O molecules. The formate can be directly oxidized into CO 2 and H 2 O in the presence of large amounts of surface hydroxyl groups . The active oxygen species on the surface of manganese oxide catalysts are the surface hydroxyl groups, surface lattice oxygen species and surface active chemisorbed oxygens (O 2− , O − etc.)…”

Molecular Insights into NO-Promoted Sulfate Formation on Model TiO2 Nanoparticles with Different Exposed Facets

“…This indicates that the produced OH can be associated with the dissociation of water molecules in oxygen vacancies existing on the highly low-coordinated TiO 2 . Especially for the (001) facet, the richness of oxygen defects derived from its highly low-coordinated structures is most favorable for the production of OH (Figure b). , It is commonly recognized that the OH groups are principal sites for the adsorption of SO 2 , as presented by the consumption of OH along with the simultaneous generation of sulfate at 400 °C in this study. ,, The OH (3725, 3680 cm –1 ) consumption and OH (3652 cm –1 ) generation arise together on T010 and T101 at 180 °C (Figure b). The consumed OH can be offset by the generated OH, or otherwise their bands overlapped, thus no observation of the negative bands of OH on T001 at low temperatures.…”

“…The high-frequency region of 3750–3600 cm –1 is dominated by several narrow and partly resolved bands of OH groups. − It has been proposed that the band near 1615 cm –1 can be assigned to the dissociated adsorption of H 2 O, which may originate from the water molecules present in the gas flow. , There was the same trend of OH with adsorbed water as the temperature increased. This indicates that the produced OH can be associated with the dissociation of water molecules in oxygen vacancies existing on the highly low-coordinated TiO 2 .…”