Adsorptive separation of acetylene from light hydrocarbons by mesoporous iron trimesate MIL-100 (Fe)

Abstract

A reducible Metal–organic Framework (MOF), iron (III) trimesate, denoted as MIL-100 (Fe), was investigated for the separation and purification of methane/ethane/ethylene/acetylene and an acetylene/CO₂ mixtures by using sorption isotherms, breakthrough experiments, Ideal Adsorbed Solution Theory (IAST) calculations and IR spectroscopic analysis. The MIL-100 (Fe) showed high adsorption selectivity not only for acetylene and ethylene over methane and ethane, but also for acetylene over CO CO₂. The separation and purification of acetylene over ethylene was also possible for MIL-100 (Fe) activated at 423 K. According to the data obtained from operando IR spectroscopy, the unsaturated Fe^III sites and surface OH groups are mainly responsible for the successful separation of the acetylene/ethylene mixture, whereas the unsaturated Fe^II sites have a detrimental effect on both separation and purification. The potential of MIL-100 (Fe) for the separation of a mixture of C CO₂H CO₂/CO CO₂ was also examined by using the IAST calculations and transient breakthrough simulations. Comparing the IAST selectivity calculations of C CO₂H CO₂/CO CO₂ for four MOFs selected from the literature, the selectivity with MIL-100 (Fe) was higher than those of CuBTC, ZJU-60a and PCP-33, but lower than that of HOF-3.