Effect of SO₂ on Na₂ZrO₃ sorbent for CO₂ capture: An experimental and density functional theory study

Sodium Zirconate (Na₂ZrO₃) has gained significant research attention for flue-gas CO₂ capture due to its good cyclic stability and relatively high capacity. However, the effect of impurity gases such SO₂ in flue gas on CO₂ capture performance has not yet been studied and the related mechanism remains unclear, which impedes the practical application of Na₂ZrO₃-based CO₂ capture technology. This study systematically investigated the performance and mechanism of Na₂ZrO₃ in the individual and competitive sorption of SO₂ and CO₂ through a combination of experiments, characterization techniques, and density functional theory (DFT) calculations. Experimental results revealed that the presence of SO₂ decreased the cyclic CO₂ capture performance (when O₂-present during the sorption stage), attributed to the reaction between SO₂ and Na₂ZrO₃ to form Na₂SO₄, which is thermally stable at operation conditions. Moreover, increasing SO₂ concentrations led to more pronounced reductions in CO₂ capture capacity, accompanied by progressive accumulation of sulfation products. DFT calculations indicated that, during competitive sorption, SO₂ not only permanently occupied active sites of plane through stable configurations, but its sulfation products also progressively deactivated neighboring sorption sites within a certain radius, thereby significantly suppressing CO₂ sorption capacity. This study elucidates the negative impact of SO₂ on Na₂ZrO₃-based CO₂ sorption performance from experimental evaluation to DFT study, providing fundamental insights and a theoretical basis for the future industrial applications in flue-gas CO₂ removal.