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.