Name: Dr. Georgia Pappa
Tel:  +30 210 772 31 37
Address: Heroon Polytechniou 9, 157 80 Zographou, Athens, GREECE

Diploma, Chemical Engineering, Aristotle University of Thessaloniki, Greece, 1993.

Ph.D., Chemical Engineering, National Technical University of Athens, Greece, 2002.

  Research Assistant, National Technical University of Athens, 2001-today.

Full CV

Recent Research Activities
Phase equilibrium modelling of ionic liquid solutions

Ionic liquids (ILs) steadily gain wide recognition as environmentally benign alternatives of volatile organic solvents in a variety of physical and chemical processes. Ionic liquids are molten salts or molten oxides with melting points below 100oC. Moreover, they are often in the liquid state at ambient or even lower temperatures, referred to as Room-Temperature ILs (RTILs). The increasing attention paid for ILs from both the industrial and the academic community stems from their unique properties such as negligible vapor pressures, non-flammability, high thermal stability, high electrical conductivity, large electrochemical window, wide liquid range, good solvating properties for diverse kinds of materials. On top of that, ILs are characterized as designer solvents since it is possible to finely tune their intrinsic thermophysical properties by simply changing the cation and/or the anion, making them appropriate for a specific application.

A systematic research in the field of ionic liquids takes place only the last few years, where ionic liquids are examined more and more instead of the conventional organic solvents not only in chemical reactions but also in separation methods.

With a view of a better understanding of the usage of ionic liquids for chemical reactions or separation processes, the knowledge of thermodynamic properties and, especially, phase equilibrium is needed.  In the framework of this project conventional  thermodynamic models, such as UNIFAC, are investigated as for their ability to model phase equilibrium in mixtures containing ionic liquids.

More information and detailed results can be found in:

- E. Alevizou, G. Pappa, E. Voutsas, "Prediction of phase equilibrium in mixtures containing ionic liquids using UNIFAC", Fluid Phase Equil., 284/2 (2009) 99.

Phase equilibrium of natural gas mixtures (The project is financially supported by STATOIL, Norway)

One of the gas quality specifications used for ensuring safe transport of natural gas is the dew point of the mixture. Avoiding hydrocarbon condensation is crucial since the presence of liquids in the pipelines increases the pressure drop and introduces operational problems resulting from the two phase flow in pipelines designed for single phase transportation. Thus, accurate prediction of hydrocarbon dew point temperatures and pressures are of great importance to obtain a safe and effective utilization of the natural gas pipelines.

Cubic equations of state (EoS), such as the Peng-Robinson (PR) and Soave-Redlich-Kwong, coupled with the classical van der Waals mixing rules, are usually implemented by the oil and gas industry for the design of recovery and processing operations of natural gases.

Previous studies have pointed out that currently all thermodynamic models have difficulty in representing correctly the whole phase envelope with both the cricondentherm and the cricondenbar.

In the framework of this project the performance of the UMR-PRU model that has been developed in our laboratory is tested in the prediction of experimental dew point data of synthetic and real natural gases.

The Universal Mixing Rule (UMR) is a mixing rule for cubic equations of state (CEoS) applicable to all type of system asymmetries. For the cohesion parameter of the CEoS the mixing rule involves the Staverman-Guggenheim part of the combinatorial term and the residual term of the original UNIFAC Gibbs free energy expression. For the co-volume parameter of the CEoS the quadratic concentration dependent mixing rule is used with the combining rule for the cross parameter. The UMR is applied to the Peng-Robinson equation of state leading to what is referred to as the UMR-PRU model.

In this project the applicability of UMR-PRU was extended to natural gas mixtures. Very satisfactory predictions were obtained for both the cricondentherm and the cricondenbar.

Phase equilibrium in associating mixtures: The Cubic-plus-Association (CPA) EoS

The Cubic Plus Association (CPA) is an equation of state (EoS) developed in our laboratory that is suitable for describing associating fluids. The equation combines the simplicity of a cubic equation of state (Soave-Redlich-Kwong or Peng-Robinson), which is used for the physical part and the theoretical background of the perturbation theory employed for the chemical (or association) part. Excellent description is obtained of both vapor pressures and saturated liquid volumes of pure associating compounds such as alcohols, phenols, glycols, acids and water.

In the framework of this project CPA has been also successfully applied to the correlation and prediction of phase equilibria (vapour-liquid, liquid-liquid, vapor-liquid-liquid) in a variety of systems where association is present.

More information and detailed results can be found in:

- E. Voutsas, Ch. Perakis, G. Pappa, D. Tassios, "An Evaluation of the Performance of the Cubic-Plus-Association Equation of State in Mixtures of non-Polar, Polar and Associating Compounds: Towards a Single Model for non-Polymeric Systems", Fluid Phase Equil., 261/1-2 (2007) 343.
- G. Pappa, C. Perakis, I. Tsimpanogiannis, E. Voutsas, "Thermodynamic Modeling of the vapor–liquid equilibrium of the CO2/H2O mixture", Fluid Phase Equil., 284/1 (2009) 56. 

Experimental measurements and modelling in acid gas-alkanolamine-water solutions

The most mature acid gas (CO2, H2S) capture processes rely on the use of amine solvents to wash acid gases out of a gas mixture, such as flue gas.  The accurate design of acid gas treatment processes requires the knowledge of vapor-liquid equilibrium (VLE) of aqueous alkanolamine solutions containing acid gas.

In the framework of this project experimental VLE measurements and thermodynamic modeling of aqueous solutions containing 2-amino-2-methyl-1-propanol (AMP) were carried out.

More information and detailed results can be found in:

- G. Pappa, Ch. Anastasi, E. Voutsas, "Measurement and Thermodynamic Modeling of the Phase Equilibrium of Aqueous 2-amino-2-methyl-1-propanol Solutions", Fluid Phase Equil., 243 (2006) 193.