Excess molar volume of binary mixtures containing an oxygenate

Abstract

Increasing fuel demand, environmental concern, and occasional oil crises brought the use of oxygenated compounds as fuel additives to improve octane/cetane rating of fuel. These oxygenates are the oxygen containing compounds such as ethers, alcohol, and esters of vegetable oils. In order to study the interactions of oxygenate with gasoline components, excess molar volumes (VmE) for 2-propanol + benzene or toluene or xylenes mixtures were reported. The VmE values, for an equimolar composition, follow the sequence: benzene > m-xylene > p-xylene > toluene > o-xylene. The excess volume data were interpreted in terms of a Graph-theoretical approach and the Prigogine–Flory–Patterson theory. While the Graph-theoretical approach yielded information about the state of aggregation of pure components as well as of the mixtures, the PFP theory correctly predicts the values as well as the sign and shape of curves for benzene containing mixtures but for other systems, predicted values were smaller for x1 < 0.4 and higher thereafter than the corresponding experimental values. Partial molar volumes, excess partial molar volumes, and apparent molar volumes of 2-propanol and aromatic hydrocarbons were also calculated from VmE data and interpreted qualitatively.