رفتار جذبي Co2 و CH4 در غشاهاي پليمري شيشه اي و توصيف تحليلي مدل عدم تحرك جزيي

Sorption Behavior of C02 and CH4 of Glassy Polymeric Membranes and Analytical Discussion of Partial Immobilization Model

Among various reported membrane-based gas separation processes, the best explanation is generally achieved by the solution-diffusion model. The main factors in this model are the solubility and diffusivity of perme¬ation components through the membrane. The prediction of permeability and diffusivity in multicomponent gas permeation as well as the separation evaluation equilibrium and kinetic interactions requires a proper explanation of sorption and diffusion phenomena in the polymer matrix. Investigation made by various researchers in this area shows that the equilibrium interaction (sorption step) plays the key role in determining diffusion and permeation in multicomponent system. Therefore, the proper description of sorption behaviour of gas mixture in the polymer is an essential task. The dual-mode sorption (Langmuir-Henry) is usually used for the description of equilibrium isotherm of gases in glassy polymers based on this model; the diffusive behaviour of the system is subsequently analyzed by the partial immobilization model. In this study, the equilibrium sorp¬tion of C02/CH4 mixture in various polymers was modelled using the experimental data available in the litera¬ture. The differences in the mechanism of adsorption for C02 and CH4 were analyzed by considering variations in mode of sorption for each adsorbed component at different pressures. By introducing a new adsorption param¬eter, P50/50, (the pressure at which the portion of two modes in sorption are equal the contribution of each adsorbed component in occupying Langmuir sites was evaluated. The results indicate that the relative signifi¬cance of sorption mode for each component is a function of pressure and it is different for various polymers.