Estimation of the critical constants of heavy hydrocarbons for their treatment by the Soave–Redlich–Kwong equation of state

Expressions were derived for the estimation of the critical constants of C7+ hydrocarbons from their normal boiling point and specific gravity at 60°F. Experimental critical temperatures were reproduced closely, while the critical pressures were adjusted to reproduce the boiling points at both 10 and 760 mm Hg by the Soave–Redlich–Kwong (SRK) equation of state. The proposed method ensures a greater accuracy in predicting heavy hydrocarbonsʹ vapor pressures below their normal boiling points, with respect to using critical constants estimated by the common literature methods. The developed equations can be applied to hydrocarbons with normal boiling points from 90° to 525°C.