Ion-exchanged SAPO-34 membranes for light gas separations

Ion exchange of H–SAPO-34 zeolite membranes with Li+, Na+, K+, NH4+, and Cu2+ cations in non-aqueous solutions increased CO2/CH4 ideal and separation selectivities up to 60%, but increased H2/CH4 ideal and separation selectivities less than 18%. Ion exchange decreased permeances, and the decrease was larger for large cations, apparently due to steric hindrance. Exchange did not degrade SAPO-34 crystals or membranes, but changed adsorption properties for some ions.