Application of the step potential for equilibria and dynamics (SPEAD) method to bioderived esters and acetals

The Step Potential for Equilibria and Dynamics (SPEAD) model, which is a combination of discontinuous molecular dynamics simulation and thermodynamic perturbation theory, has been used to study the thermodynamic equilibrium properties of potential biofuel blending compounds. Step potentials and site sizes for predicting vapor pressures and liquid densities of secondary alcohols, esters, and cyclic ethers have been optimized. Fifty two (52) compounds were simulated for either parametrization or bench-marking. Twelve (12) new groups are parametrized in this work, which are present in secondary alcohols, esters, cyclic C5 compounds, and cyclic ethers. Errors in predicted vapor pressures are generally in the range of 10%, except in the case of multifunctional cyclic compounds, where errors of 30%-70% were found. Also, bubble points are measured for a mixture of 4-hydroxymethyl-1,3-dioxolane and 5-hydroxy-1,3-dioxane, which are superimposed on the literature data and do not suggest a significant difference in the vapor pressures of the two compounds.