Sulfur Dioxide Capture by Heterogeneous Oxidation on Hydroxylated Manganese Dioxide

摘要

Here we demonstrate that sulfur dioxide (SO_2) is efficiently captured via heterogeneous oxidation into sulfate on the surface of hydroxylated manganese dioxide (MnO_2). Lab-scale activity tests in a fluidized bed reactor showed that the removal efficiency for a simulated flue gas containing 5000 mg·Nm~(-3) SO_2 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 SO_2 with terminal hydroxyls. Both H_2O and O_2 are essential for the generation of reactive terminal hydroxyls, and the indirect role of O_2 in heterogeneous SO_2 oxidation at low temperature was also revealed. We propose that the high reactivity of terminal hydroxyls is attributed to the proper surface configuration of MnO_2 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 SO_2 capture.