Modelling VLE of supercritical CO_2 + alkanol mixtures using RG-CPA EOS

Considering the contribution of association and the density fluctuations,an equation of state(EOS)based on the original cubic-plus-association(CPA)EOS and the renormalization group theory(RG)was extended to binary mixtures.The binary interaction parameters were obtained by fitting the vapor-liquid equilibrium(VLE)data at one temperature,and then were used to predict the VLE data at other temperatures.The RG-CPA EOS was used to predict the VLE and the critical line of the supercritical CO2-1-alkanol(n=1—8)binary mixtures,which are nonideal systems with association.Using temperature independent binary interaction parameters,satisfactory results for composition and density of both vapor and liquid phases were obtained by the RG-CPA EOS.The overall average absolute derivations of composition in liquid and vapor were 0.032 and 0.019 respectively.In addition,the RG-CPA EOS can successfully reproduce the vapor liquid critical line of these binary mixtures,which is much better than the original CPA EOS.