Directly synthesized high-silica CHA zeolite for efficient CO2/N2 separation

Carbon dioxide capture is an effective method to mitigate climate change . Highly CO 2 -selective and highly moisture-resistant absorbent is essential for energy-efficient carbon capture by absorption. Herein, a highly CO 2 -selective and high-silica CHA zeolite in a pure lithium form (Li-SSZ-13) was synthesized using a direct synthesis method for the first time. The effects of gel n (SiO 2 )/ n (Al 2 O 3 ) ratio, gel n (SiO 2 )/ n (Li 2 O) ratio and synthesis time on the crystallinity , yield, micropore volume and CO 2 loading of the crystals were systematically investigated. The adsorption isotherms of CO 2 and N 2 were measured for directly synthesized Li-SSZ-13, conventional Na-SSZ-13 and ion-exchanged Li-Na-SSZ-13 zeolites. The dynamic breakthrough adsorption properties were measured for Li-SSZ-13 in comparison with Na-SSZ-13 and Li-Na-SSZ-13. The obtained Li-SSZ-13 exhibited a high CO 2 adsorption capacity of 4.48 mmol/g and a high CO 2 /N 2 IAST selectivity of 310 at 100 kPa and 273 K, which were 45.0   % and 441   % higher than Na-SSZ-13 zeolite, 24.8   % and 179   % higher than Li-Na-SSZ-13 zeolite, respectively. It suggests that directly synthesized Li-SSZ-13 zeolite has great potential for efficient CO 2 capture from flue gas .