TY - JOUR
T1 - Sorption and Diffusion of Methane, Carbon Dioxide, and Their Mixture in Amorphous Polyethylene at High Pressures and Temperatures
AU - Yang, Yafan
AU - Nair, Arun Kumar Narayanan
AU - Sun, Shuyu
N1 - KAUST Repository Item: Exported on 2021-06-11
Acknowledgements: We thank the support of this work by the Dow Chemical Company. We also thank Yabin Sun and Jozef Van Dun at Dow for useful discussions.
PY - 2021/5/12
Y1 - 2021/5/12
N2 - Molecular dynamics (MD) simulations are performed to study the sorption and transport properties of CH4 and CO2 in amorphous polyethylene at temperatures from 350 to 600 K and pressures up to 500 bar. The uptake of CH4 and CO2 by polyethylene generally increased with increasing pressure and decreasing temperature. However, at high pressures, for example, the uptake of methane by polyethylene increases with temperature. The self-diffusion coefficients of methane and carbon dioxide generally increase with pressure. These results are, in general, consistent with the swelling behavior of the polymer. Interestingly, for the penetrants, the activation barrier of diffusion decreases with pressure. MD simulations are also carried out for the CH4/CO2 mixture in amorphous polyethylene. Here, the overall sorption and transport properties were similar to those reported for pure CH4 and pure CO2 in polyethylene. The sorption selectivity of CO2/CH4 decreases with increasing pressure and temperature and was mostly independent of the bulk mole fraction of methane. Importantly, at high pressures, the mobility of methane found here is higher than that of the corresponding pure methane in polyethylene and the opposite trend is observed in the case of carbon dioxide. These results might be due to the fact that the swelling of the polymer in the presence of carbon dioxide is significantly higher than that in the presence of methane, especially at high pressures. The diffusion and membrane selectivities of carbon dioxide/methane show a similar trend to the sorption selectivity data. Furthermore, the simulation data were in good agreement with the theoretical calculations based on the PC-SAFT equation of state.
AB - Molecular dynamics (MD) simulations are performed to study the sorption and transport properties of CH4 and CO2 in amorphous polyethylene at temperatures from 350 to 600 K and pressures up to 500 bar. The uptake of CH4 and CO2 by polyethylene generally increased with increasing pressure and decreasing temperature. However, at high pressures, for example, the uptake of methane by polyethylene increases with temperature. The self-diffusion coefficients of methane and carbon dioxide generally increase with pressure. These results are, in general, consistent with the swelling behavior of the polymer. Interestingly, for the penetrants, the activation barrier of diffusion decreases with pressure. MD simulations are also carried out for the CH4/CO2 mixture in amorphous polyethylene. Here, the overall sorption and transport properties were similar to those reported for pure CH4 and pure CO2 in polyethylene. The sorption selectivity of CO2/CH4 decreases with increasing pressure and temperature and was mostly independent of the bulk mole fraction of methane. Importantly, at high pressures, the mobility of methane found here is higher than that of the corresponding pure methane in polyethylene and the opposite trend is observed in the case of carbon dioxide. These results might be due to the fact that the swelling of the polymer in the presence of carbon dioxide is significantly higher than that in the presence of methane, especially at high pressures. The diffusion and membrane selectivities of carbon dioxide/methane show a similar trend to the sorption selectivity data. Furthermore, the simulation data were in good agreement with the theoretical calculations based on the PC-SAFT equation of state.
UR - http://hdl.handle.net/10754/669514
UR - https://pubs.acs.org/doi/10.1021/acs.iecr.0c06110
UR - http://www.scopus.com/inward/record.url?scp=85106501540&partnerID=8YFLogxK
U2 - 10.1021/acs.iecr.0c06110
DO - 10.1021/acs.iecr.0c06110
M3 - Article
SN - 0888-5885
JO - Industrial & Engineering Chemistry Research
JF - Industrial & Engineering Chemistry Research
ER -