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

Abstract

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