Computational Studies of Toluene, Methyl Ethyl Ketone, Lubricating and Their Blends: a Combination of Density Functional Theory and Molecular Dynamics

The microstructure and intermolecular interaction of toluene (TOL), methyl ethyl ketone (MEK), lube oil, TOL-MEK solvents, and TOL-MEK-oil solutions were studied by molecular simulation. Some simulation results agree well with the experiment, which suggests that the simulation method we adopted is a powerful tool to obtain microscopic property of the systems. The density functional theory (DFT) calculation results suggest that the interaction group of toluene and MEK is the methyl group of theirs. And the interaction between toluene and MEK is attractive. The contribution of van der Waals interaction to the change of total energy of the TOL-MEK system is major, and the second is electrostatic interaction. Molecular dynamics (MD) simulation analyzes the solubility parameter (SP), mean square displacement (MSD), radius of gyration (RG), and radial distribution function (RDF) of solvents and solutions. The results are that the solubility parameter of the blend solvents decreases with temperature, and increases with the proportion of methyl ethyl ketone in principle, and that of lube oil also trends to decrease with temperature. The MSD results give one reason of why the transmission rate of MEK is greater in membrane separation process of recovery toluene and MEK and the permeation flux increases with MEK:TOL. The RG analysis predicts that the permeability of the oil molecule is likely to rise with temperature during dewaxing solvent recovery process by membrane. The analysis of RDFs shows that the intermolecular interaction of C center dot center dot center dot C, O center dot center dot center dot O and C center dot center dot center dot O makes a major contribution to the total interaction energy.