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

Document Type: Original Research Paper

Authors

1 Environmental and Occupational Hazards Control Research Center, Shahid Beheshti, University of Medical Sciences, Tehran, Iran.

2 Department of Science and Engineering, Abhar branch, Islamic Azad University, Abhar, Iran.

3 Department of Chemistry, Faculty of Basic Sciences, University of Neyshabur, Neyshabur, Iran.

4 Department of Chemistry, Faculty of Science, University of Zanjan, P.O.Box 45195-313, Zanjan, Iran

5 Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.

6 Department of Chemistry, Faculty of Science, University of Zanjan

10.22034/jna.2018.579591.1118

Abstract

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

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