Adsorption of propane and propylene on M-MOF-74 (M = Cu, Co): Equilibrium and kinetic study

Abstract

In this study, adsorption equilibria and kinetics of propane and propylene on Cu-MOF-74 and Co-MOF-74 were investigated at temperatures of 303, 323, 343 and 363K and pressures up to 100kPa. Pure component adsorption isotherms and uptake curves were determined via volumetric method. Dual Site Sips model could better fit the experimental data than the Langmuir and Sips models. Isosteric heat of adsorption and IAST selectivity were calculated using Dual Site Sips model. Both adsorbents showed high affinity toward propylene over propane due to the presence of the open metal sites in their structure. Obtained results showed that Cu-MOF-74 exhibits higher selectivity (12.7) to propylene as well as higher adsorption capacity (7.6mmol/g) compared to Co-MOF-74, making this material as one of the most favorable adsorbents for propane/propylene separation which has been studied so far. The diffusion time constants of the adsorbates were also calculated by measuring transient uptake curves. Results indicated that the micropore diffusion model could predict the data points accurately. The rapid uptake of the adsorbates along with cyclable property suggest the Cu-MOF-74 as a highly reliable adsorbent for propane/propylene separation via vacuum pressure swing adsorption.