Molecular dynamics analysis of compositional effects in hydrocarbon systems property calculations

Uddin, Mafiz; Coombe, D.; Ivory, John

doi:10.1016/j.cej.2016.05.080

Cited by 11 publications

(6 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The identification of surrogate fuels with specific properties has been the subject of much study. ,,,− Molecular simulations can be used to both examine a broader compositional phase space than is experimentally feasible and to elucidate specific structure–property relationships of these surrogate mixtures. ,− ,, The ability to predict the properties of pure hydrocarbons and mixtures from their composition via MD simulation depends directly upon the accuracy of the underlying potential model. Herein, liquid properties and molecular structures of binary mixtures of n -hexadecane and alkylbenzenes were examined using MD simulations and the OPLS-AA potential with the L-OPLS parameter set.…”

Section: Discussion and Summarymentioning

confidence: 99%

“…MD simulations have been used to calculate a wide range of liquid hydrocarbon properties such as density, heat of vaporization, heat capacity, diffusion coefficients, and viscosity. , In a previous work, the ability of two atomistic force fields, the modified Lennard-Jones adaptive intermolecular reactive empirical bond-order potential (mod-LJ AIREBO) and the all-atom optimized potential for liquid simulations (OPLS-AA), to calculate densities, heats of vaporization, and bulk moduli for pure and multicomponent hydrocarbon liquids was compared. Uddin et al recently used the OPLS-AA force field for hydrocarbon system property calculation and quantifying physical properties of oils . Recently, Verma et al also used the OPLS-AA force field, in conjunction with the L-OPLS parameters developed by Siu et al for long-chain alkanes, to predict densities and viscosities of pure-component and binary sytems of n -octane, n -dodecane, n -hexadecane, and n -decylbenzene at temperatures and pressures up to 423.15 K and 5000 bar, which are typical fuel injection conditions in modern common rail diesel engines.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Impact of Molecular Structure on Properties of n-Hexadecane and Alkylbenzene Binary Mixtures

et al. 2018

View full text Add to dashboard Cite

Because of the complexity of petroleum-based fuels, researchers typically use simplified mixtures, known as surrogates, to study combustion behavior and to attempt to identify how physical properties are related to combustion. The process of determining the surrogate composition to yield a desired set of thermophysical properties can be a complicated and time-consuming task. As a result, the use of computer simulations to narrow the number of possible surrogate compositions is beginning to be explored. Herein, molecular dynamics (MD) simulations are used to model binary mixtures of n-hexadecane with either benzene, toluene, n-ethylbenzene, n-propylbenzene, or n-butylbenzene. Calculated densities are in quantitative agreement with experimental values. With the exception of the mixtures containing benzene, simulated excess molar volumes are also in very good agreement with measured values. Isentropic bulk moduli are in qualitative agreement with experiment, and reproduce interesting trends observed in the experimental data. Specifically, minima in the bulk moduli at intermediate compositions of several of the alkylbenzenes are correctly reproduced. In addition, the structures of the fluids are also examined. For mixtures of n-hexadecane with alkylbenzenes with longer chains, the orientation of the aromatic rings is not substantially impacted by composition. In contrast, increasing n-hexadecane content increases the ratio of parallel to perpendicular arrangements of benzene and toluene molecules. In those mixtures, this change in orientation of the aromatic rings could be responsible for the minima observed in the bulk moduli data. These results show that MD simulations can assist in development of fuel surrogates, both by predicting thermophysical properties and by providing insight into how molecular structure and composition affect those properties.

show abstract

Section: Discussion and Summarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of Molecular Structure on Properties of n-Hexadecane and Alkylbenzene Binary Mixtures

et al. 2018

View full text Add to dashboard Cite

show abstract

“…We chose the physical conditions that are relevant to the reservoir conditions. The representative oil composition used in the Simulating Aggregation Behavior in an Oil Mixture section is presented in Table . Each one of the simulations had 27 molecules of asphaltene, then the number of molecules for the other components in the systems are calculated accordingly on a weight % basis.…”

Section: Methodsmentioning

confidence: 99%

Asphaltene Aggregation in Oil and Gas Mixtures: Insights from Molecular Simulation

2019

View full text Add to dashboard Cite

The dynamics of asphaltene molecules is highly impacted by both the nature of the solvent and the physical conditions of the system. We performed molecular simulation to investigate the dynamic behavior of asphaltene during gas flooding. We also consulted the experimental observations for validation purposes when available. Two structures representing the archipelago and continental types are used, whose aggregation and interactions are studied in methane (C1), propane (C3), carbon dioxide (CO2), heptane (C7), and toluene as pure solvents, binary mixtures of toluene and either C1, C3, or CO2, and a representative oil composition. The continental structure is used afterward to evaluate the impact of temperature, pressure, and resin content on the aggregation dynamics in CO2 mixtures. Interestingly, the solvating power of CO2 is dependent on the asphaltene structure where inhibitor-like behavior is observed for the continental structure and precipitator-like behavior is observed for the archipelago structure. The solvent quality is highly correlated with the solvent s ability to replace the interactions among asphaltene molecules with interactions between asphaltene and solvent. The aggregate size is reduced by temperature and enhanced by pressure in CO2. However, limited effect is reported for resins on asphaltene dynamics in CO2. The aggregation of asphaltene is impacted by the physical state of CO2 as its solvating power to asphaltene is significantly enhanced in its supercritical state. Nonetheless, this impact is limited when CO2 is introduced to a representative oil mixture.

show abstract

“…Both Monte Carlo (MC) and molecular dynamics (MD) simulations can be used to predict fuel thermophysical properties. MD simulations are commonly used to calculate relevant properties, such as density, , bulk modulus, , viscosity, ,,, and diffusion coefficients, , of hydrocarbons typically found in fuels. Previous work has involved calculating the density, bulk modulus, and heat of vaporization of pure and multicomponent hydrocarbon fluids at ambient conditions .…”

Section: Introductionmentioning

confidence: 99%

Vapor–Liquid Equilibrium Simulations of Hydrocarbons Using Molecular Dynamics with Long-Range Lennard-Jones Interactions

Harrison

2019

Energy Fuels

View full text Add to dashboard Cite

Because of exposure of injected fuel to extreme temperatures and pressures in modern diesel and jet engines, there is much interest in understanding vapor−liquid equilibrium (VLE), interfacial behavior, and critical properties of hydrocarbon mixtures. Molecular dynamics (MD) simulations with long-range dispersion interactions can be used to study liquid−vapor interfacial properties. In this work, the accuracy of three force fields (CHARMM, OPLS-AA, and TraPPE-UA) is assessed by using MD simulations with the Lennard-Jones particle-mesh Ewald method to examine the VLE behavior of 12 pure hydrocarbons. While the TraPPE-UA potential yields significantly better critical temperature predictions, all three force fields predict critical densities and pressures with about the same accuracy. Surface tensions calculated using the TraPPE-UA force field are too high compared to experiment; values using the CHARMM and OPLS-AA potentials tend to be more accurate at lower temperatures and then decrease too quickly as temperature increases. Simulations of binary mixtures show that both the CHARMM and TraPPE-UA potentials predict the same liquid-and vapor-phase compositions as a function of overall mole fraction. Not surprisingly, the composition of the interfacial region is correlated with the surface tension values of the pure components. Pressure versus mole fraction phase diagrams were quantitatively reproduced by TraPPE-UA and only qualitatively reproduced by the CHARMM force field. Given the lack of phase equilibrium data used in the parameterization of the CHARMM potential, its ability to reproduce many aspects of VLE behavior is impressive. This work demonstrates the power of MD simulations for examining the phase behavior of hydrocarbons under conditions that are difficult to achieve experimentally.

show abstract

Molecular dynamics analysis of compositional effects in hydrocarbon systems property calculations

Cited by 11 publications

References 30 publications

Impact of Molecular Structure on Properties of n-Hexadecane and Alkylbenzene Binary Mixtures

Impact of Molecular Structure on Properties of n-Hexadecane and Alkylbenzene Binary Mixtures

Asphaltene Aggregation in Oil and Gas Mixtures: Insights from Molecular Simulation

Vapor–Liquid Equilibrium Simulations of Hydrocarbons Using Molecular Dynamics with Long-Range Lennard-Jones Interactions

Contact Info

Product

Resources

About