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

Abstract

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. Mn4+/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.