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University of Tennessee Department of Chemical Engineering |
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University of Tennessee Department of Chemical Engineering |
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The Thermophysical Properties Measurement Laboratory (TPML) high energy components of designer gasolines and diesel fuels We are interested in increasing the energy content of gasolines and diesel fuels by hydrogenating aromatic compounds currently in these fuels. The saturated components have a higher energy of combustion than do the aromatic compounds. (As a simple example, the heat of combustion of benzene is -3266.0 kJ/mol, while the heat of combustion of cyclohexane is -3916.5 kJ/mol.) As a result of the increased energy content, the miles traveled in an automobile per unit of CO2 produced will be increased. This is an essential feature in the reduction of the rate of generation of green house gases. In order to explore the feasibility of this hydrogenation in the refinery, which of course would occur in the presence of a myriad of other reactions, we require the enthalpy, entropy, and free energy of the hydrogenation reactions. Currently we are using quantum mechanical calculations to estimate the enthalpy, entropy, and free energy of hydrogenation of various aromatic compounds. Among the tasks is the calculation of the complete vibrational spectra of each molecule, so that we can determine the contribution to the entropy of the vibrational degrees of freedom. We consider dimethylnaphthalene as our sample aromatic compound. Dimethylnaphthalene has ten isomers, depending on the placement of the methyl groups. The properties have been determined experimentally for only a few of these isomers. Currently, we are generating the properties via quantum mechanical calculations for those isomers for which experimental data has been measured. We use this set of data to determine the optimal choice of quantum mechanical method and basis set for this class of compounds. We will then use this method to calculate the desired properties for the remaining isomers. Two isomers of dimethylnaphthalene are shown below, one in a still image and the other in an interactive box (if you have installed the free Chime plug-in): |
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1,7-dimethylnaphthalene |