Investigation of Physical Chemistry Properties of Asphaltenes Using Solubility Parameters of Asphaltenes and Their Fractions Al and A2

摘要

The Sphere method developed by Hansen (Hansen, C. M. Hansen Solubility Parameters: A User's Handbook; CRC Press: Boca Raton, FL, 1999) to calculate components of solubility parameters (SP), δ_D dp, and δ_H, where D, P, and H stand for dispersion, polar, and hydrogen bonding respectively, have been applied to resins, to asphaltenes, and fractions Al and A2. Mean values for these compounds in MPa~(0.5) were asphaltenes (19.5 ±0.1,4.7 ±0.2,4.2 ± 0.1); A2 (19.6 ±0.1,5.8 ±0.1,4.4 ± 0.2); Al (20.9 ±0.2,5.6± 0.3,6.8 ± 0.2); resins (18.6 ± 0.2, 3.6 ± 0.3, 3.2 ± 0.3). Also, the SP components of the asphaltene sample (AsH-NS), denuded from acidic natural surfactant (NS), were determined affording values equal to A2. These values were obtained after using 57 solvents, and the method is consistent with all known solubility properties of asphaltenes and confirm the expected solubility behavior of Al and A2, with A1 being the less soluble material in all solvent examined. Excellent affinity between asphaltene with resins was predicted as well as affinity between samples examined. These results are coherent with a colloidal model whereby fraction Al is in not contact with the solvent, being within a core shielded from the media by a periphery composed by fraction A2 and NS. Flocculation results measured in n-_C7- 1-methylnaphthalene mixtures correlate with the above SP showing the following order of flocculation tendency: A1? A2 > asphaltenes (AsH). We also observed that flocculation points of A2 and AsH-NS were very close, and this strongly supports the colloidal model above. SP were helpful in analyzing other properties such as adsorption, vaporization, affinity, and molecular mass and paraffin's properties.