Study on CO₂ Adsorption Properties and DFT Mechanism of Sulfur-resistant Potassium-based Adsorbents

After desulfurization and denitrification in coal-fired power plants, the trace amount of SO₂ can lead to the failure of potassium-based adsorbents. In this paper, aerogel carriers are prepared by using sol-gel method, and modified potassium-based adsorbents are prepared by using the impregnation method doped with MnO₂. With the help of a fixed bed decarburization experimental system, the decarburization experiments of the adsorbents are carried out under different conditions. Avrami adsorption kinetic model is used to fit, and the pore, phase composition and microscopic appearance of the adsorbents are analyzed by combining characterization methods. Based on density functional theory (DFT), the anti-sulfur mechanism of Mn-doped modified adsorbents is explored in depth. The results show that: in an atmosphere containing 150 mg/m³ SO₂, MnO₂ reacts with SO₂ to form MnSO₄, reducing the reaction between SO₂ and K₂CO₃, and the CO₂ adsorption capacity is increased by 29.7%. The adsorbents have certain sulfur resistance. The optimal doping amount of MnO₂ is 2.5%, the optimal adsorption conditions are 12.5% CO₂ concentration, 60℃ reaction temperature, and 15% H₂O concentration. The adsorption energy of SO₂ on the adsorbent surface is the largest, and the 2p orbitals of S and O atoms and the 3d orbitals of Mn atom in SO₂ molecule resonate and interact with each other, thus having a certain anti-sulfur effect. After Mn doping, the reaction energy barrier is decreased to 143.71 kJ/mol, and the reaction heat is increased to −164.92 kJ/ mol, thereby reducing the influence of SO₂ on the decarburization performance of the adsorbent. MnO₂-doped modified potassium-based adsorbents exhibit significant sulfur resistance and high CO₂ adsorption capacity in SO₂-containing atmosphere.