Type 3 Porous Liquids for the Separation of Ethane and Ethene

We assess the potential for formulating a porous liquid that could be used as a selective solvent for the separation of ethane and ethene. Ethane-ethene separation is performed on very large scales by cryogenic distillation, but this uses large amounts of energy. Solvents that are selective to ethane or ethene could potentially enable more efficient liquid-based separation processes to be developed, but such solvents have been elusive to date. Here, Type 3 porous liquids, which consist of mi-croporous solids dispersed in size-excluded liquid phases, have been tailored toward the separation of ethane and ethene. High selectivity for ethene over ethane (25.6 at 0.8 bar) and high capacity was achieved for zeolite AgA dispersed in an Ag-containing ionic liquid. Unusually for liquid phases, selectivity for ethane over ethene (2.55 at 0.8 bar) could also be achieved using the MOF Cu(Qc)2 (Qc = quinoline-5-carboxylate) dispersed in sesame oil, or ZIF-7 in sesame oil, the latter showing gated uptake. The efficiency of the Cu(Qc)2 synthesis was increased by developing a mechanochemical method. Regeneration of Cu(Qc)2 in sesame oil and ZIF-7 in sesame oil was also demonstrated suggesting that these or similar porous liquids could potentially be applied in cyclic separation processes.