Principal Investigators

Athanassios Panagiotopoulos
Pablo Debenedetti
Jeroen Tromp

At a Glance

Molecular-based computational tools for predicting fundamental physical and chemical characteristics of H2O+CO2 and H2O-NaCl binary systems are being developed to help interpret the rational design of CO2 separation processes and long-term CO2 storage in geological formations.

 

Research Highlight

Over the past year, the research collaboration between Panagiotopoulos and Debenedetti (CBE), and Tromp (Geosciences) has focused on obtaining the phase behavior and transport properties for the H2O+CO2 and H2O-NaCl binary systems. For the engineering design of carbon dioxide (CO2) sequestration processes, accurate predictions of properties for these mixtures at conditions found in geological reservoirs are required. Experimental data are often not available over the complete range
of conditions of interest; predictive, molecular-based models coupled with computer simulations can reliably interpolate and (it is hypothesized) extrapolate from limited experimental information. These simulations can also help discriminate among conflicting sets of experimental data.

The research group found that phase partitioning and interfacial properties of these systems can be predicted with moderate accuracy using existing atomistic models. However, it appears that future modeling needs will require development of improved force fields (intermolecular potential models). Several force field combinations were examined for the H2O+NaCl system and used to calculate the vapor pressure, liquid density, viscosity and vapor-liquid interfacial tension as a function of salt content. The group has also optimized the intermolecular potential parameters for the H2O+CO2 system1 in an attempt to reconcile conflicting sets of experimental measurements2,3, as shown in Figure 2.4.

Figure 2.4. On left, a schematic representation of a two-phase system with a CO2-rich top phase and a H2O-rich bottom phase; on right, the composition of the coexisting phases predicted from simulations with different models (points) and sets of experimental data (lines)1. There is significant disagreement among experimental measurements1-2 for the top (CO2-rich) phase.

The long-term goals of this work include the development of reliable, molecular-based models for the thermophysical and adsorption properties of components and systems involved in geological carbon sequestration. The group plans to focus efforts on the development and testing of polarizable force fields4,5, which can accurately capture both aqueous and non-aqueous solution environments. These have not been as well developed as non-polarizable force fields because of their higher computational cost.

 

References

  1. Orozco, G.A., I. G. Economou, and A. Z. Panagiotopoulos, 2014. Optimization of Intermolecular Potential Parameters for the CO2/H2O Mixture. J. Phys. Chem. B, 118: 11504-11511. doi:10.1021/jp5067023.
  2. Todheide, K., and E.U. Frank, 1963. Das Zweiphasengebie Und Die Kritische Kurve Im System Kohlenoxid-Wasser Bis Zu Drucken Von 3500 bar. Z. Phys. Chem. Neue Folge, 37: 387−401.doi:10.1524/zpch.1963.37.5_6.387.
  3. Takenouchi, S., and G. C. Kennedy, 1964. Binary system H2O-CO2 at high temperatures + pressures.Am. J. Sci., 262: 105.
  4. Paricaud, P., M. Predota, A. A. Chialvo, and P. T. Cummings, 2005. From dimer to condensed phases at extreme conditions: Accurate predictions of the properties of water by a Gaussian charge polarizable model. J. Chem. Phys., 122: 244511. doi:10.1063/1.1940033.
  5. Kiss, P.T., and A. Baranyai, 2013. A systematic development of a polarizable potential of water. J.Chem. Phys., 138: 204507. doi:10.1063/1.4807600.