(739h) A Robust Iron Based Metal-Organic Framework PCN-250 for Adsorption Separation of C2H6 over C2H4

Authors: 
Xia, Q., South China University of Technology
Li, Z., South China University of Technology
Chen, Y., South China University of Technology
Qiao, Z., National University of Singapore
Xiao, J., South China University of Technology
Xi, H., South China University of Technology
Zhou, J., South China University of Technology
Energy-saving separation C2H4/C2H6 mixture is of great importance and challenge. In this work, we reported a robust iron based metal-organic framework, PCN-250, as a C2H6-selective adsorbent with a high uptake of C2H6 and adecent selectivity towards C2H6/C2H4 separation. Adsorption isotherms of C2H4 and C2H6 were measured and their adsorption capacities were high up to 4.22 and 5.21 mmol/g at 298 K and 100 kPa, respectively. More importantly, it exhibited preferential adsorption of C2H6 over C2H4.The adsorption selectivities of C2H4/C2H6 mixtures (15:1 and 1:1, v/v) were in the range of 1.85-4 on the basis of ideal adsorbed solution theory (IAST). Meanwhile, its separation performance was also verified by the breakthrough experiments, indicating the potential of C2H4 purification from C2H4/C2H6 mixture, particularly for industrial C2H4 purification of removing low concentration of C2H6 from the cracked gas mixture (C2H4/C2H6, 15:1). The isosteric heats of C2H6 and C2H4 calculated by Clausius-Clapeyron equation gradually increased from 23.6 to 27.8 and 21.1 to 25.3 kJ/mol, respectively. The isosteric heats adsorption of C2H6 and C2H4 on PCN-250 were much lower compared to those π-complexation adsorbents preferentially adsorbing C2H4. Configurational-biased grand canonical Monte Carlo (CB-GCMC) method was employed to simulate its adsorption behaviors in PCN-250 and reveal the mechanism underlying the preferential adsorption and separation of C2H6 over C2H4. Computational simulation results showed that the exceptional C2H6 selectivity was attributed to the effect of steric hindrance and revealed that the small pore of PCN-250 was a key factor governing the separation of C2H6 and C2H4, especially in low pressure. The highethane adsorption capacity, high C2H6 /C2H4 selectivity and low isosteric heat of adsorption of PCN-250 would make it a promising adsorbent for the effective separation of ethane/ethylene.