Modelling sorption and diffusion of NF3 and CF4 in Teflon AF perfluoropolymer membranes

• Published in: Journal of membrane science Vol. 470; pp. 294 - 306
• Main Authors: Branken, D.J., Krieg, H.M., Lachmann, G., Carstens, P.A.B.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.11.2014; Elsevier
• Subjects: Applied sciences; Chemistry; Colloidal state and disperse state; Exact sciences and technology; Exchange resins and membranes; Forms of application and semi-finished materials; General and physical chemistry; Grand canonical Monte Carlo simulations; Membranes; Molecular dynamics; NELF model; NF3/CF4 membrane separation; Polymer industry, paints, wood; Surface physical chemistry; Technology of polymers; Teflon AF; NF3/CF4 membrane separation; Molecular dynamics; NELF model; Grand canonical Monte Carlo simulations; Teflon AF; Polymeric membrane; Monte Carlo method; CF; Sorption; Membrane separation; Adsorption; Simulation; NF; Models; Diffusion
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2014.07.033

Molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations with Teflon AF2400 and Teflon AF1600 predicted diffusivities and solubilities of He and N2 that corresponded reasonably with available experimental data. The results of the MD simulations further showed that NF3 had a higher diffusivity than CF4 in both polymers and that the NF3/CF4 diffusion selectivity was 67% higher in Teflon AF1600 compared to Teflon AF200. However, because the GCMC simulations failed to offer a conclusive answer to the role of the solubility selectivity w.r.t. NF3 and CF4, the non-equilibrium lattice fluid (NELF) model was used to further evaluate this aspect. Consequently, the combined NF3/CF4 diffusion and solubility selectivity values predicted permeability selectivities that corresponded well with the previously reported experimental data, which confirmed that a lower FFV resulted in an increased NF3/CF4 solubility and diffusion selectivity. [Display omitted] •3D atomistic packing models of Teflon AF 1600 and AF2400 were constructed.•The models were validated using He and N2 diffusivity and solubility data.•NF3 was calculated via MD to have a higher diffusivity than CF4 in both polymers.•The NELF model predicted that NF3 also has a higher solubility in both polymers.•The predicted NF3 and CF4 permeabilities correlated with experimental results.