Density Functional Theory-Based Adsorption Isotherms for Pure and Flue Gas Mixtures on Mg-MOF-74. Application in CO2 Capture Swing Adsorption Processes

A simplified model is applied for the prediction of gas/solid adsorption isotherms of pure gases (i.e., CO2, N-2, SO2) on the metal-organic framework Mg-MOF-74 and then applied to flue gas mixtures with small amounts of SO2 in the range 0.001-1% in weight. The model is based on periodic density functional theory (DFT) calculations and a dual-site Langmuir approach (DFT/DSL), using a mean-field approximation for the inclusion of the lateral interactions. This model not only provides reliable adsorption isotherms (P <= 1 atm, 293 <= T <= 373 K) but also isosteric heats of adsorption in good agreement with both available experimental data and more refined previous models. Moreover, the effect of SO2 in the efficiency of adsorption of the other components of the mixture has been evaluated by showing that a very low presence of SO2 is enough to poison the Mg-MOF-74 structure. Finally, several swing adsorption techniques have been analyzed at different operative conditions to quantify the impact of SO2 poisoning in the CO2 adsorption.