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

The development of exceptionally stable porous solid physisorbents is vital for deep flue gas desulfurization (FGD) and SO2 recovery, as the corrosive and reactive nature of SO2 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 SO2 adsorption performance. Na-SSZ-13 exhibits excellent water, thermal, and chemical stability, high SO2 affinity and adsorption kinetics with extraordinary SO2/CO2 separation selectivity (2673 at zero coverage, 298 K), and exceptional low-concentration SO2 adsorption capacity (4.6/2.7 mmol g-1 at 0.1/0.002 bar) with the highest surface-specific SO2 uptake among reported zeolites. Column breakthrough experiments demonstrate efficient SO2 capture capability from a quaternary flue-gas mixture at high temperature (323 - 423 K). Moreover, it achieves 96.5% purity of the recovered SO2 during the regeneration process, and shows fully reversible SO2 uptake and excellent cycling stability. GCMC simulations, DFT calculations, and in situ DRIFT analyses reveal a selective SO2 adsorption mechanism with the counter-cations (Na+) serving as primary SO2 adsorption sites, elucidating the role of cation···SO2 interactions that underpin the application of zeolite-based materials for deep FGD under high-temperature and low-concentration working conditions.