The new Waxphaltene Determinator method is based on the on-column precipitation and redissolution separation technique developed at Western Research Institute. Although high-performance liquid chromatography (HPLC) instrumentation and detectors are used, the separation does not involve chromatographic interaction between the material being separated and the stationary phase. It is based on freezing, melting, and solubility. The Waxphaltene Determinator uses methyl ethyl ketone at −24 °C to precipitate waxes and asphaltenes. The precipitated material is redissolved in four steps using a series of three solvents of increasing polarity, at different temperatures: heptane at −24 °C, heptane at 60 °C, toluene at 30 °C, and methylene chloride/methanol (98:2, v/v) at 30 °C. This approach allows for the detection of waxy, polar, and pericondensed aromatic components in minutes.

A simple dual-mechanism model successfully fits the oxidation of 12 unmodified asphalt binders originating from a wide variety of sources. The kinetic formulation includes fast and slow reaction paths in parallel with free radical interactions between the two reaction pathways. The same Arrhenius parameters are used for all 12 binders studied. The differences in asphalt binder oxidation rates can be explained with the use of only one adjustable parameter, the amount of reactive material available for the fast reaction. This result suggests that unmodified asphalt binders oxidize with essentially the same chemical mechanisms. Because the Arrhenius parameters apply universally, a simple test may be performed to characterize the oxidation kinetics for unmodified binders without expensive, long-term oxidation experiments at multiple temperatures. A rheological study of the materials generated in the aging of the 12 binders using dynamic shear rheometry was also performed to investigate the relationship of rheological changes with chemical changes as binders oxidize. The rheometry consisted of the generation of a series of isothermal frequency sweeps, followed by fitting the resulting master curve with the Christensen–Anderson model. Simple shifting cannot account for the master curve changes, but changes in the model parameters follow a log-linear relationship for oxidation chemical changes. These fits appear to be source dependent, suggesting that a method with two aging time conditions would be required to characterize the rheological property changes in an unmodified asphalt binder as it ages. Such a method would produce a complete master curve–shift function set at any extent of aging, suitable for input into rational performance models.

Various techniques were used to compare the effectiveness of a commercially available wax inhibitor (WIA) to a newly developed wax inhibitor (WIEP) using a highly waxy Wyoming crude oilwhich causes plugging within wellbores and pipelines. The two additives were compared using centrifuge experiments, cold finger tests, and the precipitation and redissolution waxphaltene determinator (WD) method. Centrifuge tube experiments, and cold finger tests, showed that the newly developed WIEP additive was significantly more effective at reducing the amount of ambient temperature wax crystallites in the crude oil, as well as reducing the amount of wax deposited on a cold finger. WD analysis was performed on model compounds to differentiate between shorter and longer n-paraffins. Whole crude oils, ambient temperature waxes centrifuged from the oils, and waxes from cold finger deposits were also analyzed by the WD method. Taken together with high temperature gas chromatography, the WD profile of whole crude oils readily distinguishes shorter n-paraffins from the more problematic longer n-paraffins that are prone to crystallization at ambient temperature. For treated Elliott crude oil, the WD Analysis profile showed a consistent decrease in wax with WIA concentration to give a linear correlation; however, a less consistent change was observed with the WIEP additive. By applying the WD analysis to the additives themselves, it was elucidated that the WIEP additive contained components that were highly polar and/or more associated. This observation suggests that components in the WIEP additive may self-precipitate to a greater degree than becoming incorporated with the waxes during the WD separation. This effect caused the WIEP to appear as though it is not as effective as the WIA additive in the WD analysis.

Model compounds were used to provide some chemical boundaries for the eight-fraction SAR-ADTM characterization method for heavy oils. It was found that the Saturates fraction consists of linear and highly cyclic alkanes; the Aro-1 fraction consists of molecules with a single aromatic ring; the Aro-2 fraction consists of mostly 2 and 3-ring fused aromatic molecules, the pericondensed 4-ring molecule pyrene, and molecules with 3–5 rings that are not fused; and the Aro-3 fraction consists of 4-membered linear and catacondensed aromatics, larger pericondensed aromatics, and large polycyclic aromatic hydrocarbons. The Resins fraction consists of mostly fused aromatic ring systems containing polar functional groups and metallated polar vanadium oxide porphyrin compounds, and the Asphaltene fraction consists of both island- and archipelago-type structures with a broad range of molecular weight variation, aromaticity, and heteroatom contents. The behavior of the eight SAR-ADTM fractions during hydrocracking and pyrolysis was investigated, and quantitative relations were established. Intercriteria analysis and evaluation of SAR-ADTM data of hydrocracked vacuum residue and sediment formation rate in commercial ebullated bed vacuum residue hydrocracking were performed. It showed that total asphaltene content, toluene-soluble asphaltenes, and colloidal instability index contribute to sediment formation, while Resins and Cyclohexane-soluble asphaltenes had no statistically meaningful relation to sediment formation for the studied range of operation conditions.

A physicochemical approach was taken to show wax-based and crude oil-based differences between three waxy crudes (Amenam, Norne, and Varandey), that had similar amounts of wax according to DSC crystallizable areas, that were responsible for very different responses to pour point depressant additive treatments. Varandey crude oil was the most difficult to treat, and the effectiveness of the additives decreased with time when the oil had been aged for 2 years prior to treating with the additives. Detailed compositional analysis of these three crude oils, and their waxes, showed that Varandey contains the highest concentration of longer n-paraffins, significantly more total n-paraffins, a higher wax appearance temperature, the highest amount of wax that can be centrifuged at ambient temperature, a bimodal distribution of crystallizable waxes by DSC, more saturates in the heavy ends by the Saturates, Aromatics, Resins-Asphaltene Determinator, a very high amount of Waxphaltene Determinator Waxy B (−24 °C methyl ethyl ketone precipitated waxes that do not dissolve in heptane at that temperature but melt at 60 °C in heptane) and very little asphaltenes that do not flocculate. These additional characterization methods, including the wax appearance temperature, show that the amount of wax by DSC is not discriminating for some crude oils. Microscopy of Varandey showed large fractal crystalline domains that were different from Amenam, which showed classic large macrocrystalline needle-like crystals, or Norne that had a gelled network with much smaller needle-like crystals. Norne is less responsive to additive treatment than Amenam despite having significantly less n-paraffins, Waxphaltene Determinator Waxy B waxes, and asphaltenes. Simulated distillation shows that Norne is the heaviest oil and has the highest amount of isomeric material in the C24−C34 range and a higher temperature wax appearance temperature. Furthermore, its asphaltenes flocculated with the addition of isooctane at 60 °C, whereas the asphaltenes did not flocculate in Amenam. The higher amount of isomeric material by GCMS and the much smaller needle-like crystallites suggest that Norne wax is more microcrystalline in nature. Centrifuging Varandey waxes and doping them into Amenam and Norne resulted in the doped crude oils having a bimodal DSC profile with a higher wax appearance temperature. The presence of Varandey wax caused the oils to be significantly less responsive to pour point additive treatments. Overall, for these relatively similar crude oils, it is shown that the nature of the highest carbon number waxes, the wax appearance temperature, and the amount of the least soluble waxes are significantly more important than the crude oil composition when treating with additives since they will dictate the temperature at which n-paraffins first self-associate leading to crystal nucleation.