Properties of asphaltenes precipitated with different n-alkanes.: A study to assess the most representative species for modeling

This work deals with the study of asphaltene precipitation from a +190 degrees C residue at different temperatures, using several n-alkanes and n-alkane/oil ratios. Experiments were carried out at the boiling point of the solvent (IP-143 standard) and at other temperatures in order to elucidate if asphaltene yields are conditioned by the nature of the solvent and/or by the boiling temperature of the alkanes. The results show that lower asphaltene yields were obtained when using solvents with higher molecular weights at the same temperature, but also when using higher temperatures with the same solvent. Consequently, both effects that simultaneously influence asphaltene precipitation could be conveniently separated. Preliminary characterization of the asphaltenes obtained at different conditions has been carried out by means of NMR spectroscopy and elemental analysis. Further characterization has focused on the particle size distributions obtained during kinetic tests of asphaltene flocculation by a laser reflectance technique (focused-beam reflectance measurement, FBRM): significant differences have been obtained, all related to the n-alkane and ratio used in the flocculation.