STUDY OF ASPHALTENE AGGREGATION IN TOLUENE/n- HEPTANE/CO2 MIXTURES AT HIGH PRESSURE CONDITIONS

Abstract

In this work we present a novel experimental method to obtain asphaltene precipitation envelope (APE) of complex systems composed by toluene/nheptane mixture in presence of CO2 at high pressure and different temperatures. The method has the feasibility to detect phase changes of asphaltenes in a pressure range from 1 to 100 MPa and temperatures from 283 to 473 K. For the first time a complete APE using experimental data was obtained. The solubility behavior of the asphaltenes with the pressure of the system is in agreement with previous studies. However the temperature aggregation behavior at high pressure showed a minimum near to 353 K that contrasts with reported data. This complex tendency can be explained by changes in viscosity, density and aggregate composition with temperature. Also, the coexistence of two subfractions A1 and A2 in the asphaltenes and their differences in solubility modifies the solubility and the entropy variation of the system can help to understand the asphaltene aggregation behavior at higher temperatures.