Predictive evaluation of phase equilibria in biofuel systems using molecular thermodynamic models

• Predictive analysis of phase equilibria of biofuel systems using molecular models.
• GC-PPC-SAFT and molecular simulation representing systems at low and high pressures.
• Evaluation of different association schemes to describe the glycerol molecule.
• Heat of mixing of different systems predicted by GC-PPC-SAFT.

In this work an analysis of the predictive capacity of two molecular models was evaluated on phase equilibrium of systems involved in the biofuel processing. Group Contribution- Polar Perturbed- Chain Statistical Associating Fluid Theory (GC-PPC-SAFT) and Monte Carlo simulation were used. Predictive multiphase equilibria at low and high pressures were computed for alcohol + ethyl or methyl esters, alcohol + glycerol, water + glycerol and ethanol + water. An analysis of different association schemes of glycerol was performed. Heat of mixing was also used to assess the behavior of some systems. The predictions showed to be consistent with VLE data, with deviations <5% for alcohols + esters and alcohols + glycerol, water + glycerol; and 5.4% for ethanol + water. Studies using heats of mixing predicted by GC-PPC-SAFT and structural information provided by molecular simulation indicated the Scheme 4C is the most appropriate to describe the glycerol molecule.

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