Crossover soft-SAFT modelling of the CO2+NO2/N2O4 mixture

Abstract

Accurate thermo-physical properties are mandatory for all industrial applications. However, experimental data are often scarce and models are needed for the estimation of properties. Such is the case in supercritical processes like the selective oxidation of vegetal macromolecules in mixture NO2/N2O4 – supercritical CO2 aiming at producing body-degradable polymers readily usable for inside body surgery. The so-called crossover soft-SAFT equation of state is used to model the pure compounds and the mixture. The quadrupolar effect is explicitly considered when modeling carbon dioxide, obtaining excellent agreement for the whole phase equilibrium diagram. NO2 is modeled as a self associating molecule with a single association site. Finally, CO2 and NO2 pure compound parameters are used to predict the vapor – liquid coexistence of the CO2 + NO2 / N2O4 mixture at different temperatures. Experimental pressure – CO2 mass fraction isotherms recently measured are used for comparison. Good agreement is obtained with the use of a unique binary parameter, independent of thermodynamic conditions, although more experimental data would be useful to conclude about the accuracy of the calculation.