A simulation study of methane-hydrogen gas mixture permeation through nanoporous palladium membrane using molecular dynamics

Abstract

We conducted molecular dynamic (MD) calculations to explore the efficiency of H2/CH4 separation through nanoporous palladium membrane. A palladium membrane with engineered-porosity of 0.1%–2.2% is used in our model of gas component separation from a mixture. We use computations of molecular dynamics to measure many trajectories of the molecules and thereby collect low statistical uncertainty projections of the gas flow rates. Our simulations demonstrate that high porosity palladium membranes are permeable to both gasses. As the porosity decreases, the permeability of larger molecules greatly reduced, which contributes to an exclusion effect of molecular size for a range of porosity that can permit smaller molecules. This implies that the determined porosity can achieve high selectivity in the separation of gas molecules while the desired gas molecules exhibiting high permeability. We also found that external driving force has a good effect on hydrogen permeation mechanism through a membrane. The gas flux of hydrogen levels increases as the pressure difference increases. The real mechanism of hydrogen permeability can also be visualized through our simulation, showing time dependence of flux, selectivity and pressure dependence. This work is expected to provide the framework for the development of an energy-efficient palladium-based gas separation system.