Solubility of CO2 in Aqueous Solutions of Hyperbranched Polymers. Search for Green Process Solvents
Advancing the chemical engineering fundamentals
Thermodynamics: General (T2-1e)
Keywords: hyperbranched polymers, green solvent, carbon dioxide, phase equilibria
Hyperbranched polymers (HBPs) have recently attracted much interest due to their physical, thermal and chemical properties. Compared with dendrimers, which are highly uniform and monodisperse polymers [1], HBPs are randomly branched, three-dimensional and polydisperse and they can easily be synthesized via economically favorable one-step reactions. Seiler et al. [2-4] showed that HBPs develop preferred interaction with one compound of a mixture, or in thermodynamic terms, that the fugacities of components in mixtures are selectively altered by the HBPs. This finding suggests that HBPs can be used as solvent or additive in separations based on adsorption to increase separation performance. By controlled functionalization of the end groups the properties of hyperbranched polymers can be tailored. Therefore, HBPs are potential green solvents for large-scale industrial applications like e.g. cleaning waste gases from carbon dioxide. In contrast to the conventional solvents these novel compounds are less flammable and have no measurable vapor pressure which results in hardly any emission to the environment.
For the purpose of determining the applicability of HBPs in the absorption/desorption cycles vapor-liquid equilibrium data are measured for aqueous solutions of Polyethylenimine (HyperPolymers GmbH) + carbon dioxide systems. The bubble point pressures of (HBPs + H2O + CO2) samples with fixed compositions were measured using a Cailletet apparatus [5]. The Molecular Dynamics (MD) simulations are performed using MACSIMUS software [6] in order to support the phase equilibrium measurements and to describe the intermolecular interactions in HBPs-CO2 systems. The transferable potentials for phase equilibria-united atom force fields (TraPPE-UA) [7-11] are used in MD simulations.
An extension of the perturbed chain statistical associating fluid theory (PC-SAFT) [12] is derived, accounting for branching, in order to correlate thermodynamic properties and phase equilibria of ternary systems with HBPs.
Literature:
[1] F. Aulenta, W. Hayes, S. Rannard, Eur. Polym. J. 39 (2003) 1741-1771.
[2] M. Seiler, D. Kohler, W. Arlt, Sep. Purif. Technol. 30 (2003) 179-197.
[3] M. Seiler, J. Rolker, W. Arlt, Macromolecules 36 (2003) 2085-2092.
[4] M. Seiler, Fluid Phase Equilib. 241 (2006) 155-174.
[5] T.W. de Loos, H. J. van der Kool, P. L. Ott, J. Chem. Eng. Data 31 (1986) 166-168.
[6] J. Kolafa, http://www.vscht.cz/fch/software/macsimus/index.html, January 2007.
[7] M. G. Martin, J. I. Siepmann, J. Phys. Chem. B 102 (1998) 2569-2577.
[8] M. G. Martin, J. I. Siepmann, J. Phys. Chem. B 103 (1999) 4508-4517.
[9] B. Chen, J. J. Potoff, J. I. Siepmann, J. Phys. Chem. B 105 (2001) 3093-3104.
[10] J. M. Stubbs, J. J. Potoff, J. I. Siepmann, J. Phys. Chem. B 108 (2004) 17596-17605.
[11] J. J. Potoff, J. I. Siepmann, AIChE J. 47 (2001) 1676-1682.
[12] J. Gross, G. Sadowski, Ind Eng. Chem. Res. 40 (2001) 1244-1260.
Presented Tuesday 18, 15:20 to 15:40, in session Thermodynamics: General (T2-1e).
