| This study aimed at characterizing a variety of crude oils with respect to their emulsion-forming capabilities and in determining the fundamental causes of refinery emulsions has yielded a number of significant findings which, if properly implemented, should help reduce refinery waste generation. The primary result is a molecular-level picture of the origins of emulsions stability which, if it proves to be general, should assist in prescribing basic crude blending and solvent-recycle schemes for minimizing emulsion formation during refinery operations. Two different methods of quantifying polar fractions of petroleum have been developed and compared to determine the most accurate and insightful fractionation technique. In addition, detailed quantitative protocols for quantifying emulsion stability have been developed and applied to the four crudes: Arab Berri (Extra Light), Arab Heavy, Alaska North Slope, and San Joaquin Valley. Elemental and neutron activation analyses as well as FTIR and {dollar}sp{lcub}13{rcub}{dollar}C NMR spectral characterizations have been developed and applied to the detailed analysis of the four crudes, particularly the polar surface-active fractions. The key results here are the accurate quantification of resin and asphaltene contents, polar functional group concentration, and aromatic carbon content in these polar fractions. A molecular model has been developed which predicts emulsion stability based on the resin-to-asphaltene (R/A) ratio in the crude, the aromaticity of the crude, and the polarity of the asphaltenes, which in turn determines the degree to which they are solvated by resins. This model was tested by correlating these key characteristics with the emulsifying propensities of the whole crudes and through the use of solvent-modified whole crudes and model oils constructed by dissolving varying amounts of resins and asphaltenes in a mixture of heptane and toluene. Dramatic destabilization of emulsions was obtained by elevating the R/A ratio and increasing the aromaticity of the medium in these systems. Interestingly, the source of the resins also played a strong role in determining how effective the destabilization was, suggesting that strongly polar resins (with high concentrations of carbonyl and carboxylate functional groups) were more effective at solvating asphaltenes and destabilizing emulsions. |
