Efficient Propylene/Ethylene Separation in Highly Porous Metal–Organic Frameworks

Light olefins are important raw materials in the petrochemical industry for the production of many chemical products. In the past few years, remarkable progress has been made in the synthesis of light olefins (C2–C4) from methanol or syngas. The separation of light olefins by porous materials is, therefore, an intriguing research topic. In this work, single-component ethylene (C2H4) and propylene (C3H6) gas adsorption and binary C3H6/C2H4 (1:9) gas breakthrough experiments have been performed for three highly porous isostructural metal–organic frameworks (MOFs) denoted as Fe2M-L (M = Mn2+, Co2+, or Ni2+), three representative MOFs, namely ZIF-8 (also known as MAF-4), MIL-101(Cr), and HKUST-1, as well as an activated carbon (activated coconut charcoal, SUPELCO©). Single-component gas adsorption studies reveal that Fe2M-L, HKUST-1, and activated carbon show much higher C3H6 adsorption capacities than MIL-101(Cr) and ZIF-8, HKUST-1 and activated carbon have relatively high C3H6/C2H4 adsorption selectivity, and the C2H4 and C3H6 adsorption heats of Fe2Mn-L, MIL-101(Cr), and ZIF-8 are relatively low. Binary gas breakthrough experiments indicate all the adsorbents selectively adsorb C3H6 from C3H6/C2H4 mixture to produce purified C2H4, and 842, 515, 504, 271, and 181 cm3 g−1 C2H4 could be obtained for each breakthrough tests for HKUST-1, activated carbon, Fe2Mn-L, MIL-101(Cr), and ZIF-8, respectively. It is worth noting that C3H6 and C2H4 desorption dynamics of Fe2Mn-L are clearly faster than that of HKUST-1 or activated carbon, suggesting that Fe2M-L are promising adsorbents for C3H6/C2H4 separation with low energy penalty in regeneration.