Water effect on adsorption carbon capture in metal-organic framework: A molecular simulation

Abstract

Considering water vapor is a component in almost all CO2-rich industrial gas streams, it is of critical importance to understand interaction mechanisms between adsorbent and adsorbate. This paper aims to comprehensively analyze water effect on CO2 adsorption for metal-organic framework (MOF) in a broad working pressure range which may bring some new insights based on a molecular simulation. First, Mg-MOF-74 is selected and synthesized according to previous literature. Equilibrium adsorption capacity and enthalpy are obtained by grand canonical Monte Carlo simulation, and the results for high-pressure CO2 adsorption are validated through magnetic suspension balance experiment. It is indicated that there are three adsorption stages for pure CO2 and four adsorption stages for pure H2O under different pressure. Adsorption enthalpy also varies with adsorption capacity, which is fully explained from the angle of adsorption stages and energies. Further simulation of flue gas (CO2/H2O/N2) adsorption at different humidity are carried out, and selectivity between CO2 and H2O is analyzed. At 298 K, 100 kPa, with 3% water content, CO2/H2O selectivity is 5.6 × 10−5. When temperature rises to 388 K, CO2/H2O selectivity rises to 6.2 × 10−3. Adsorption density distributions, simulation snapshots, and radial distribution functions are used in analysis processes, which could provide a general perspective for analyzing CO2 adsorbents in the presence of H2O.