Modeling of unsteady-state permeation of gas mixture through a self-synthesized PDMS membranes

This work presents a comprehensive two-dimensional mathematical model for unsteady state permeation of pure gas and ternary gas mixture through a synthesized single layer PDMS membrane. A numerical model was established for predicting permeation behavior of pure and mixed gases, at different operating conditions of upstream temperatures, pressures and feed compositions. The time lag method was also employed to calculate the diffusion coefficient of each component in a concentration dependant system. The results achieved show that permeability of heavier gas (C3H8) decreases with increasing feed pressure and temperature, whereas those of lighter gases (H-2 and CH4) in contrary would increase. Increasing C3H8 concentration in the feed improves permeation of all components, while increasing H-2 concentration, significantly increases permeability of H-2, in comparison with those of other components. Furthermore, both the comparison between mixed and single gases permeation performances and the effect of cross-link density on PDMS membranes performances were highlighted in this study. The simulation results proved this fact that diffusivity is the dominant parameter on permeability of the lighter gases (H-2 and CH4), while solubility has the prevailing affect on permeability of the heavier gases such as C3H8. The simulated results were finally validated with independent pure gas and ternary gas mixture experiments. The results confirmed that there is a reasonable conformity between the predicted values for permeability, solubility, diffusivity and mole fraction in the permeate side of aforementioned components and experimental available data. (c) 2010 Elsevier B.V. All rights reserved.