Separation of propylene and propane by functional mixture of imidazolium thiocyanate ionic liquid‐organic solvent‐cuprous salt

Abstract This work presented the preparation of two new systems comprised of ionic liquids (ILs), organic solvent, and cuprous salt. Consequently, their absorption ability was investigated for propylene (C 3 H 6 ) and propane (C 3 H 8 ) and their mixtures at 100 kPa‐700 kPa pressure and 298 K‐318 K temperature. Representative ILs were 1‐butyl‐3‐methylimidazolium thiocyanate ([C 4 mim]SCN) and 1‐ethyl‐3‐methylimidazolium thiocyanate ([C 2 mim]SCN). N,N‐dimethylformamide (DMF) and cuprous thiocyanate (CuSCN) were selected for the absorption system. The effects of operating parameters like Cu + concentration, pressure, temperature, and recycling of ILs absorbency were examined and compared with the literature. It was observed that C 3 H 6 shows a chemical absorption while C 3 H 8 undergoes a physical one by [C 4 mim]SCN‐DMF‐CuSCN and [C 2 mim]SCN‐DMF‐CuSCN, and an increase in concentration of Cu + effectively improves the absorption capability for C 3 H 6 and the selectivity of C 3 H 6 /C 3 H 8 . Furthermore, [C 4 mim]SCN‐DMF‐CuSCN had higher absorption capability and selectivity for C 3 H 6 than [C 2 mim]SCN‐DMF‐CuSCN. [C 4 mim]SCN‐CuSCN‐2.0 M absorbed 0.637 mol of C 3 H 6 per litre while 0.16 mol of C 3 H 8 per litre at 700 kPa and 298 K, with a selectivity of 3.9. This work shows that new combination of organic solvent and ILs with Cu + salt is a new class of potential reactive absorbents to separate C 3 H 6 and C 3 H 8 .