Energy efficient ethylene purification in a commercially viable ethane-selective MOF

Abstract Separating ethane (C2H6) from ethylene (C2H4) using ethane-selective adsorbents to replace energy-intensive cryogenic distillation technology is an important energy-saving method in the petrochemical industry to obtain high purity C2H4. Limited to the low separation efficiency in current commercial materials, it is very urgent and promising to fabricate such alkane selective adsorbents using cheap ligands and simple synthesis methods, which have characteristics such as stable structure, high C2H6 uptake, and adsorption selectivity. In this work, we have used one of the cheapest ligands (terephthalic acid, H2BDC) to prepare Cu(BDC)(DMF) via a simple and easy-to-scale up solvothermal method. The activated Cu(BDC) exposed diamond-shaped one-dimensional pores form a stronger affinity with C2H6 than C2H4 through the double function of C-H∙∙∙π interactions and C-H∙∙∙O hydrogen bonds. Benefiting from the difference in these interactions, Cu(BDC) exhibited a higher adsorption capacity of C2H6 (51.5 cm3/g) compared to C2H4 (45.1 cm3/g) at 1 bar and 298 K, which resulted in high adsorption selectivity (2.0) for the C2H6/C2H4 mixture (50/50, v/v). Breakthrough experiments indicated that Cu(BDC) successfully achieved the removal of C2H6 from C2H6/C2H4 (50/50 and 10/90, v/v) mixtures to obtain high purity C2H4 (> 99.99%) using a one-step separation process. When compared with the benchmark materials, Fe2(O2)(dobdc) and NIIC-20, Cu(BDC) had the advantages of much lower preparation cost and enhanced structural stability. These comprehensive properties indicated that Cu(BDC) with a commercially viable price and synthesis process, could be potentially used for the C2H6 removal step during the production of high purity C2H4.