Mohammad Vaghefi

High-molecular-weight hydrocarbons and asphaltenes are important constituents of petroleum and can cause problems related to crystallization and deposition of asphaltene. This article introduces an extension of the cubic equation of state (Peng-Robinson EOS) to describe asphaltene–toluene mixture vapor–liquid equilibria (VLE) and characterize pure asphaltene, and the critical properties of asphaltene were adjusted. Experimental data were used to examine the proposed procedure in an Iranian crude oil reservoir. We determined the critical properties of asphaltene for this EOS using a two-phase vapor–liquid equilibrium calculation. The test results showed that the proposed procedure is adequate for predicting asphaltene precipitation data.