(441f) Modeling Aqueous Alkanolamine + Carbon Dioxide Mixtures Using the SAFT-VR Mie and SAFT-γ Mie Equations of State

An accurate description of the thermodynamic properties of fluids is useful for the design of better chemical processes. The predictive capabilities of two molecular-based equations of state are assessed: SAFT-VR Mie [1], employing a homonuclear model where each molecule is described by its own specific parameters, and SAFT-γ Mie [2], a group contribution (GC) version of SAFT in which molecules are represented by a set of functional groups, each with their own set of parameters. In common with other SAFT approaches, the molecules are described as chains of spherical segments. The segment-segment interactions are described with a Mie potential, which has been shown to provide a good prediction of the fluid-phase equilibria (including the near-critical region) and properties that are second-derivatives of the Helmholtz free energy (for example heat capacities), by allowing for varying degrees of softness/hardness of the interactions [3]. In this study we analyse the predictions obtained when modelling mixtures of aqueous alkanolamines and carbon dioxide (CO₂) that are of relevance in CO_2 capture studies. This involves the prediction of thermodynamic properties that are not considered in the development of the molecular models, and in the case of the GC approach the predictions for molecules for which experimental data are not used in the model development. The thermodynamic models are currently being used to describe process models for carbon capture and separation [4,5].

References

[1] Lafitte, Thomas, et al. "Accurate statistical associating fluid theory for chain molecules formed from Mie segments." The Journal of chemical physics, 139.15 (2013): 154504.

[2] Papaioannou, Vasileios, et al. "Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments." The Journal of chemical physics, 140.5 (2014): 054107.

[3] Dufal, Simon, et al. "Developing intermolecular�potential models for use with the SAFT�VR Mie equation of state." AIChE Journal, 61.9 (2015): 2891-2912.

[4] Brand, Charles V., et al. "On the use of molecular-based thermodynamic models to assess the performance of solvents for CO₂ capture processes: monoethanolamine solutions." Faraday Discussions (2016).

[5] Burger, Jakob, et al. "A hierarchical method to integrated solvent and process design of physical CO₂ absorption using the SAFTâ?Î³ Mie approach." AIChE Journal, 61.10 (2015): 3249-3269.