Contributions of aromatic conjunction and aromatic inner carbons to molar volume of polyaromatic hydrocarbons

A modification of our previous equation for estimation of the molar volume of hydrocarbons on the basis of atomic group contributions was made to be able to extend the applicability to a wide variety of hydrocarbons, including condensed polyaromatic hydrocarbons (CPAHC), which are main components in heavy oils. Two atomic groups were additionally selected to characterize CPAHC, namely aromatic conjunction (ac) and aromatic inner (ai) carbons. Utilizing the molar volume data for pure CPAHC in literature, increments in the molar volume by the presence of the two groups were evaluated by a regression analysis as 2.8 and 8.6 ml/mol, respectively. The molar volumes of hydrocarbon mixtures in heavy oils containing CPAHC, estimated with the above increments, agree well with those observed. The equation is applicable to polyaromatic hydrocarbons with the ring numbers up to seven in both forms of pure substances and their mixtures.