Systematic examination of the links between composition and physical properties in surrogate fuel mixtures using molecular dynamics

Properties of Two-Component Mixtures of Isobutylcyclohexane (1) or tert-Butylcyclohexane (1) with n-Dodecane (2) or n-Hexadecane (2): Densities, Surface Tensions, Viscosities, and Speeds of Sound at 0.1 MPa and Various Temperatures

“…The most probable causes of the positive excess molar volume are either changes in the volume occupied by each compound or by changes in their packing with each other because the molecules are nonpolar and would not interact by intermolecular forces other than London dispersion. In studies using molecular dynamics simulations as a way to understand excess molar volume, researchers have found that in compounds with aromatic or cyclic rings, the rings can orient themselves with respect to other rings in either a parallel or perpendicular arrangement. − For cyclohexanes with various substituents, Maskey et al reported that the probability of finding the ring in a perpendicular arrangement decreased as the length of the straight-chain substituent increased . The volume occupied by the molecule can also change.…”

“…53−55 For cyclohexanes with various substituents, Maskey et al reported that the probability of finding the ring in a perpendicular arrangement decreased as the length of the straight-chain substituent increased. 55 The volume occupied by the molecule can also change. Mixtures of n-propyl-and n-dodecylcyclohexane with n-hexadecane were found experimentally to have positive and negative excess molar volumes, respectively.…”

Binary Mixtures of Aromatic Compounds (n-Propylbenzene, 1,3,5-Trimethylbenzene, and 1,2,4-Trimethylbenzene) with 2,2,4,6,6-Pentamethylheptane: Densities, Viscosities, Speeds of Sound, Bulk Moduli, Surface Tensions, and Flash Points at 0.1 MPa

“…For all three molecules, the perpendicular arrangement (angles near 90°) is most probable, similar to previous results for a series of n-alkylbenzenes 43 and n-alkylcyclohexanes. 45 The probability of finding molecules in a parallel arrangement (angles near 0°) increases as npropylbenzene < 1,3,5-trimethylbenzene < 1,2,4-trimethylbenzene. For 50:50 mixtures of the alkylbenzenes with isododecane (Figure 7, bottom row), the probability of finding molecules with their aromatic rings in parallel arrangements increases relative to that in the pure alkylbenzene fluids.…”

“…MD simulations are not constrained by the commercial availability of compounds, are able to model temperatures and pressures that could be difficult to achieve experimentally, and can give insight into atomic-level phenomena that affect macroscopic physical properties. Previously, MD simulations were used to study surrogates consisting of binary mixtures of hydrocarbons at ambient conditions to assess the accuracy of thermophysical property predictions and increase understanding of the molecular-level behavior of hydrocarbon mixtures. − The accuracy of MD simulations depends on the quality of the force field that models the interactions between atoms. In this work, the all-atom optimized potential for liquid simulations (OPLS-AA) was used.…”

“…In this work, the all-atom optimized potential for liquid simulations (OPLS-AA) was used. This force field has previously been used to simulate hydrocarbons of various types, including linear alkanes, branched alkanes, alkylbenzenes, alkylcyclohexanes, and binary and ternary mixtures. − OPLS-AA was shown to have good agreement with experimental values for thermophysical properties such as density, isentropic bulk modulus, and dynamic viscosity. In addition, the molecular-level structure of pure alkylbenzene fluids, as characterized by radial distribution functions and angular radial distribution functions, was shown to agree well with experimental neutron diffraction data .…”