Properties of MnO₂ and Mn-Based Perovskite Oxides for SO₂ Capture under Controlled Temperature and Atmosphere

Sulfur dioxide (SO₂) is a major air pollutant generated in significant quantities during the combustion of fossil fuels. Oxidation capture of SO₂ using metal oxides offers a promising approach for flue gas purification. In this study, we employed hydrothermal and solid-state reactions to synthesize MnO₂ and perovskite-type AMnO₃ (A = Mg, Ca, Sr, Ba) adsorbents for SO₂ oxidation capture. Their SO₂ removal performance was systematically investigated under optimized conditions, spanning a temperature range of 5-800 °C and various atmospheres, including N₂, O₂, CO₂, and CO. MnO₂ exhibited excellent performance in SO₂ removal because of its strong oxidability, even though without the presence of O₂. In comparison, AMnO₃ adsorbents only worked effectively with O₂ presence. Mn^4+/3+ in the desulfurizers was reduced into Mn²⁺ species, while SO₂ was fixed as S⁶⁺ species during the captures. The catalytic oxidation of CO occurred on the surfaces of MnO₂ over 400 °C, strongly depressing the capture of SO₂. AMnO₃ (A = Ca and Sr) adsorbents showed better resistance to CO toxication during the desulfurization reactions. In comparison to MnO₂, SO₂ captures over AMnO₃ (A = Ca and Sr) were depressed by CO until the temperature reached 700 °C.