Application of the simplified PC-SAFT Equation of State to Complex Phase Equilibria of Ethylene Glycol Oligomers
Advancing the chemical engineering fundamentals
Thermodynamics (T2-1P)
Keywords: Phase Equilibria, Equation of State, PC-SAFT, glycol
The final aim of this work is to obtain a model which can be used in the development of complex products such as pharmaceuticals, polymers, detergents and food ingredients. This type of modeling is challenging due to the complexity of the molecules involved. For equations of state of the SAFT type a major limitation is due to the procedure of obtaining pure compound parameters using vapor pressure and liquid density data. These data are, for complex compounds, often not available. One solution is to develop a group contribution scheme for PC-SAFT for estimating pure compound parameters from low molecular weight data and extrapolate to complex compounds. For associating compounds this is not trivial since the two parameters for association (association energy and volume) need to be fixed. In this work results will presented for ethylene glycol oligomers with fixed association parameters. These compounds are widely used in petroleum and chemical industry e. g. ethylene glycol (MEG) is used to prevent gas hydrate formation and also as antifreeze, diethylene glycol (DEG) and triethylene glycol (TEG) are employed as dehydrating agent for natural gas, and tetraethylene glycol (TeEG) has been applied as extractant to produce high-purity aromatics. Also 1,2 propylenglycol (PG) was included in this study.
New ethylene glycol oligomers parameters were estimated which yield good results for vapour-liquid equilibria (VLE) and liquid-liquid equilibria (LLE). All glycols are assumed to have four association sites. Complex VLE and LLE in binary systems with water, hydrocarbons, aromatics, methane and CO2 were considered. Satisfying results were obtained in most cases. Various combining rules for the association parameters were applied in systems with solvation. The glycols + heptane LLE were studied; for MEG, DEG and PG very satisfying results were obtained while for TEG/TeEG + heptane larger deviations occur. In glycol + aromatics systems solvation was explicitly accounted for and very good results were obtained for glycol + aromatic LLE.
Presented Monday 17, 13:30 to 15:00, in session Thermodynamics (T2-1P).
