Dynamics and Separation-based Adsorption of Binary Mixtures of CH4, CO2 and H2S on MIL-47: GCMC and MD Studies

This study aimed to investigate the adsorption of CH4, CO2, H2S at a temperature of 298.15 K and pressurerange of 0.1 to 30 atm, and compare the results with experimental data for MIL-47 using GCMC. Themaximum CH4, CO2 and H2S adsorptions were 3.6, 10.45, and 12.57 mol.kg-1, respectively. In addition, theselectivity for binary mixtures of CH4/CO2 and CH4/H2S was calculated. The results for CH4/CO2 mixturesat 10 atm showed that: 1) MIL-47 only adsorbed CO2 in a 0.05 CH4/ 0.95 CO2 mixture, and 2) by increasingthe mole fraction of CH4, the selectivity toward CO2 decreased. The results for H2S/CH4 mixture at 10atm showed that: 1) H2S was adsorbed only in mole fractions of 0.95, 0.75, and 0.50 of H2S, and 2)the observed selectivity was about 132.7 and 63.2 at H2S mole fractions of 0.25 and 0.05, respectively.The MD simulations and RDF analyses were used to investigate 0.5 CH4/0.5 CO2 and 0.75 CH4/0.25 H2Smixtures. The results showed that the adsorption mostly occurs on the metallic part of MIL-47. Wefound that V and O atoms were the active adsorption sites in MIL-47. H2S and CH4 showed to have thehighest and lowest levels of self-diffusions, respectively. The MD simulations were used to study the selfdiffusionfor mixtures across all mole fractions. In the binary mixture of 0.95 CO2/0.05 CH4, the maximumself-diffusion was 1.49×10-12 m2s-1 for CO2. The maximum self-diffusion for H2S in the mixture of 0.05CH4/0.95 H2S was 2.62×10-10 m2s-1.