Amino-Functionalized SAPO-34 Membranes for CO₂/CH₄ and CO₂/N₂ Separation

Abstract

SAPO-34 seeds and membranes were functionalized with several organic amino cations, such as ethylenediamine, hexylamine, and octylamine. The successful incorporation of the amino groups in the SAPO-34 framework was confirmed by Fourier transform infrared (FTIR) and X-ray photoemission (XPS) spectroscopies. The resultant SAPO-34 membranes were evaluated for the separation of CO₂/CH₄ and CO₂/N₂ gas mixtures. CO₂/CH₄ selectivities as high as 245, with CO₂ permeances of ∼5 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 295K and 138 kPa, were observed for an optimum ethylenediamine-functionalized membrane, which corresponded to a ∼40% increase in the separation index, as compared to the nonfunctionalized SAPO-34 membrane. Similarly, the CO₂/N₂ separation performance was highly improved with the incorporation of ethylenediamine. CO₂/N₂ selectivities as high as 39, with CO₂ permeances of ∼2.1 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 295K and 138 kPa, were observed for an optimum ethylenediamine-functionalized membrane, which corresponded to a ∼167% increase in the separation index, as compared to the nonfunctionalized SAPO-34 membrane.