Enhanced Trace CO2 Capture on Heteroatom-substituted RHO zeolites under Humid Conditions.

In this paper, boron and copper heteroatoms were successfully incorporated into the frameworks of high-silica RHO zeolite by adopting a bulky alkali metal-crown ether (AMCE) complex as the template. As a consequence, these heteroatom-doped zeolites show both larger micropore surface areas and volumes than those of their aluminosilicate analogue. Proton-type RHO zeolites were then applied for separation of CO2 / CH4 / N2 mixtures so as to weaken the electric field of these zeolites and then decrease the adsorption heat. The adsorption results show that a balance between working capacity and adsorption heat could be achieved harmoniously on these heteroatom-doped zeolites. The ideal adsorbed solution theory (IAST) predictions further demonstrate their high selectivities even for remarkably dilute sources of carbon dioxide. Finally, the heteroatom-substituted zeolites, especially the boron-substituted one, could be thermally regenerated rapidly at 150℃ after full hydration and could maintain high regenerability up to 30 cycles, which makes them potential candidates for trace CO2 removal under humid conditions.