Molecular sieving of iso-butene from C4 olefins with simultaneous high 1,3-butadiene and n-butene uptakes

Abstract

Iso-butene (iso-C₄H₈) is an important raw material in chemical industry, whereas its efficient separation remains challenging due to similar molecular properties of C₄ olefins. The ideal adsorbent should possess simultaneous high uptakes for 1,3-butadiene (C₄H₆) and n-butene (n-C₄H₈) counterparts, endowing high efficiency for iso-C₄H₈ separation in adsorption columns. Herein, a sulfate-pillared adsorbent, SOFOUR-DPDS-Ni (DPDS = 4,4'-dipyridyldisulfide), is reported for the efficient iso-C₄H₈ separation from binary and ternary C₄ olefin mixtures. The rigidity in pore sizes and shapes of SOFOUR-DPDS-Ni exerts the molecular sieving of iso-C₄H₈, while exhibiting high C₄H₆ and n-C₄H₈ uptakes. The benchmark Henry's selectivity for C₄H₆/iso-C₄H₈ (2321.8) and n-C₄H₈/iso-C₄H₈ (233.5) outperforms most reported adsorbents. Computational simulations reveal the strong interactions for C₄H₆ and n-C₄H₈. Furthermore, dynamic breakthrough experiments demonstrate the direct production of high-purity iso-C₄H₈ (>99.9%) from C₄H₆/iso-C₄H₈ (50/50, v/v), n-C₄H₈/iso-C₄H₈ (50/50, v/v), and C₄H₆/n-C₄H₈/iso-C₄H₈ (50/15/35, v/v/v) gas-mixtures.