Basic Zeolites as Efficient Adsorbents for Removing Trace Amounts of Acetylene from Ethylene

Adsorptive separation of acetylene (C 2 H 2 ) from ethylene (C 2 H 4 ) using porous materials has emerged as an energy-efficient process for obtaining polymer-grade C 2 H 4 . Numerous microporous organometallic and organic materials have recently been developed to selectively adsorb C 2 H 2 over C 2 H 4 . In contrast, zeolites, widely used commercial adsorbents due to their stability and synthesis scalability, have rarely been explored for C 2 H 2 /C 2 H 4 separation. In this study, we synthesized faujasite (FAU) zeolite adsorbents with different basic properties by controlling Si/Al ratios, charge-balancing cations (Na + and K + ), and the amount of excess alkali oxides and investigated their performance in the C 2 H 2 /C 2 H 4 separation. The results demonstrate that zeolites with higher basicity (or with more negatively charged O atoms) exhibit a stronger interaction with C 2 H 2 through C δ− –H δ+ ···O δ− Lewis acid–base interactions. Meanwhile, larger K + extraframework cations located in more accessible supercages provide additional interactions with the abundant π-electrons of C 2 H 2 . Therefore, the KX zeolite supported with 3 wt % K 2 O clusters within its micropore (3K 2 O/KX) exhibited a high IAST C 2 H 2 /C 2 H 4 selectivity of 20.2 as well as a remarkable dynamic selectivity of 121.8 at 298 K and 1 bar for a 1/99 (v/v) C 2 H 2 /C 2 H 4 mixture. The adsorbent enabled the efficient production of high-purity C 2 H 4 (>99.9995%) from a mixture of C 2 H 2 /C 2 H 4 (1/99) with a high productivity (758.2 L kg –1 ). These findings hold promise for the development of efficient, stable, and scalable inorganic adsorbents in C 2 H 2 /C 2 H 4 separation.