Carbon-Type Composition of Viscous Fractions of Petroleum: Density–Refractivity Intercept Method

Abstract

The molecular volume and density of saturated polycyclic hydrocarbons can be calculated with a standard deviation of about 0.008. Density for polycyclic aromatic hydrocarbons can be calculated with a standard deviation of 0.007. Differences of observed density due to differences in number or type of ring structures amount to several units in the second decimal place. Therefore, it is possible to use calculated densities in evaluating carbon-type composition. Molecular volumes and densities for all the basic structures having 15, 20, 26, 30, and 40 carbon atoms have been calculated. A correlation between calculated density and refractivity intercept is presented by which carbon-type composition can be obtained for oils having between 15 and 40 carbon atoms, if the number of carbon atoms is also known. The latter may be derived from an equation based on molecular weight and viscosity-gravity constant. The correlation can be used for all types of viscous petroleum oils, including very aromatic oils which are rich in polynuclear hydrocarbons. The validity of this analytical procedure confirms the validity of the equation for calculation of molecular volume and density of polycyclic hydrocarbons. © 1958, American Chemical Society. All rights reserved.