Simulation of O2/N2 behaviors on multi-component polymeric membranes in oxy-fuel combustion system

Abstract

As a viable way to separate O2 from air, multi-component polymeric membranes exhibit excellent O2/N2 separation capability and can be considered as a potential alternative to an air separation unit (ASU) for oxy-fuel combustion. In this study, the microscopic diffusion and separation behaviors of O2 and N2 gas molecules on the blending azo-bridged porous organic polymers (AZOPOP) and poly(phthalazinone ether sulfone ketone) (PPESK) membranes were simulated and calculated using Universal Force Field (UFF) and Perdew-Burke-Ernzerhof exchange-correlation functional (PBE) for the first time. The results showed that the mean square displacement (MSD) versus simulation time is linear, and the curve at higher temperatures exhibits more fluctuation. The adsorption energy for N2 and O2 on the polymeric membrane was first calculated, and their appreciable disparity (Ead,N2 = −0.247 eV, Ead,O2 = −0.569 eV) proves that O2 is prone to being adsorbed by the AZOPOP/PPESK composite membrane This phenomenon signifies that O2 molecules have more opportunities to transverse the abundant pores in the membrane, which can be attributed to the existence of the nitrogen-phobic azo functional groups. Furthermore, reaction temperature shows a negative correction with the diffusion selectivity (αD): α323K (1.05) < α298K (1.06) < α273K (1.07).