(334b) Modeling of CO2 Scrubbing With Hyperbranched Polymers Solutions Using Lattice Cluster Theory

Authors: 
Enders, S., TU Berlin
Langenbach, K., TU Kaiserslautern
Walowski, C., TU Berlin



Concerning the global warming effect which is caused by the increase of the environmental CO2 concentration, large efforts have been made to optimize the CO2 sequestration. Until now, CO2 scrubbing using monoethanolamin solutions is the state of the art chemical adsorption process. However, this process has several disadvantages1, like high energy costs, solvent loss and salt formation. Solving the drawbacks of the classical amine systems, Rolker at al.1 suggested the application of hyperbranched polymers to achieve a physical absorption with a high selectivity and capacity for CO2. The polyamines offer very high CO2 loading because of the presence of different kinds of amino groups per molecules1. CO2 capture potential of hyperbranched polymers, like polyglycerol or polyethylene imine, were studied in the literature2,3,4. The hyperbranched polymers can by tailored by different functional terminal groups and the architecture of the polymer in terms of degree of branching or molecular weight. Until now, the modeling of the gas solubility was performed using the classical approaches, like UNIFAC-FV1,4 or PC-SAFT2,3. Both methods are not able to take the architecture of the hyperbranched polymer into account. The purpose of this contribution is the investigation of the impact of the polymer architecture on the gas solubility in hyperbranched polymer solutions.

Recently, phase equilibria of mixtures containing hyperbranched polymers could be modeled using Lattice Cluster Theory (LCT), developed by Freed and coworkers5,6, in a compressible (LCT-EOS)7,8,9 or in a non-compressible10 fashion. In order to model the gas solubility the LCT-EOS is applied. This approach allows the systematic investigation of impact of the polymer architecture on the gas solubility. This is possible, using a cluster expansion of the partition function that incorporates a molecule’s structure through a set of combinatorial numbers describing its united-atom architecture. For a given architecture of a hyperbranched polymer the combinatorial numbers involved in the LCT-EOS can be obtained by a graph theoretical approach7. The theoretical results were compared with experimental data taken from the literature1,2.

Literature

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3 C.S. Schacht, S. Bahramali, D. Wilms, H. Frey, J. Gross, T.W. de Loos, Phase Behavior of the system hyperbranched polyglycerol + methanol + carbon dioxide. Fluid Phase Equilibria 299 (2010) 252-8.

4 S. Stünkel, W. Martini, H. Arellano-Garcia, G. Wozny, Entwicklung eines optimalen CO2-Abtrennungsprozesses. Chemie Ingenieur Technik 83 (2011) 448 – 495.

5 J. Dudowicz, K.F. Freed, Effect of Monomer Structure and Compressibility on the Properties of Multicomponent Polymer Blends and Solutions: 1. Lattice Cluster Theory of Compressible Systems. Macromolecules 24 (1991) 5076-5095.

6 J. Dudowicz, M.S. Freed, K.F. Freed, Effect of Monomer Structure and Compressibility on the Properties of Multicomponent Polymer Blends and Solutions: 2. Application to Binary Blends. Macromolecules 24 (1991) 5096-5111.

7 K.O. Langenbach, S. Enders, Development of an Equation of State Based on Lattice Cluster Theory for Pure Components. Fluid Phase Equilibria 331 (2012) 58–79.

8 K. Langenbach, S. Enders, C. Browarzik, D. Browarzik, Calculation of the high pressure phase equilibrium in hyperbranched polymer systems with the Lattice-Cluster Theory. J. Chem. Thermodynamics 59 (2013) 107–113.

9 K. Langenbach, D. Browarzik, J. Sailer, S. Enders, New Formulation of the Lattice Cluster Theory Equation of State for Multi-Component Systems. in preparation.

10 T. Zeiner, D. Browarzik, S. Enders, Calculation of the liquid-liquid equilibrium of aqueous solutions of hyperbranched polymers. Fluid Phase Equilibria 286 (2009) 127-133.