The UNIFAC-NRF group contribution activity coefficient model is used for the calculation of vapor-liquid equilibria of binary systems of the heavy alkanes and light gases such as CH4, C2H6, CO2 and N-2. The linear combination mixing rule, LCVM, of the Huron-Vidal and Michelsen, Chen et al. modification of PSRK and Universal Group Contribution Equation of State of Ahlers and Gmehling are combined with the UNIFAC-NRF group activity coefficient model to correlation of the vapor-liquid equilibrium of both light and heavy hydrocarbons. The results show that the LCVM mixing rule combing with UNIFAC-NRF group contribution model correlate the asymmetric systems better than the LCVM-UNIFAC and the other EOS/G(E) models. Also the group contribution model is used for the prediction of the phase envelope of the synthetic fluid with accurate results. (C) 2009 Elsevier B.V. All rights reserved.