Solubility and interaction parameters as references for solution properties II: precipitation and aggregation of asphaltene in organic solvents.

The total combinatory Gibbs free energy was successfully used to model the solubility of two purified asphaltenes in pure and mixed solvents, as well as the precipitation of asphaltenes from mixed solvents. Intrinsic viscosity and aggregate size both sensitively reflected the state of the asphaltenes in homogeneous solution and were used for determining the solubility parameters of the asphaltenes. Phase separation was clearly reflected by a dramatic increase in aggregate size. The interaction parameter was subdivided into enthalpy and entropy contributions. All parameters indicate an extensive association or phase transition when the phase boundary was followed by simultaneously varying the temperature and the solubility parameter of the solvent. However, the interaction parameter is frequently derived in two ways. We show that, depending on the definition, the enthalpy and entropy contributions lead to conflicting results. These were evaluated on thermodynamic grounds.

Characterization of ozonated vegetable oils by spectroscopic and chromatographic methods.

In this work the effect of ozonation on olive oil, soybean oil, oleic-, linoleic- and linolenic acid was studied. The effects of ozonation time on the oils and acids were analyzed by 1H, 13C NMR. Further, the peroxide- and acid values, the viscosity and the molar mass were determined for pure and ozonated oils. The fatty chains in both ozonated oils showed a gradual decrease of unsaturation with the gradual increase of ozonation time. Reaction products were identified according to Criegee mechanism. The major product in the early stage of the reaction was ozonide. The disappearance of unsaturation and formation of ozonide was almost equal. Ozonation increased the peroxide and acid values for both oils, the increase being higher for soybean oil. After long ozonation times higher molar mass species, as well as low molar mass species were observed. These are interpreted as oligomeric ozonides and cross-ozonides, respectively.