High‐Temperature and Low‐Concentration Deep Flue Gas Desulfurization with Low‐Si/Al (∼5)‐Ratio Zeolite Na‐SSZ‐13

ABSTRACT The development of exceptionally stable porous solid physisorbents is vital for deep flue gas desulfurization (FGD) and SO ₂ recovery, as the corrosive and reactive nature of SO ₂ restricts the applicability of most porous materials in this demanding scenario. Herein, we report the synthesis of microporous SSZ‐13 zeolite to obtain the exceedingly stable Na‐SSZ‐13 with low‐Si/Al‐ratio (5:1), and systematically evaluate its dynamic SO ₂ adsorption performance. Na‐SSZ‐13 exhibits excellent water, thermal, and chemical stability, high SO ₂ affinity and adsorption kinetics with extraordinary SO ₂ /CO ₂ separation selectivity (2673 at zero coverage, 298 K), and exceptional low‐concentration SO ₂ adsorption capacity (4.6/2.7 mmol g ⁻¹ at 0.1/0.002 bar) with the highest surface‐specific SO ₂ uptake among reported zeolites. Column breakthrough experiments demonstrate efficient SO ₂ capture capability from a quaternary flue‐gas mixture at high temperature (323 – 423 K). Moreover, it achieves 96.5% purity of the recovered SO ₂ during the regeneration process, and shows fully reversible SO ₂ uptake and excellent cycling stability. GCMC simulations, DFT calculations, and in situ DRIFT analyses reveal a selective SO ₂ adsorption mechanism with the counter‐cations (Na ⁺ ) serving as primary SO ₂ adsorption sites, elucidating the role of cation···SO ₂ interactions that underpin the application of zeolite‐based materials for deep FGD under high‐temperature and low‐concentration working conditions.