The colloidal structure of bitumen: Consequences on the rheology and on the mechanisms of bitumen modification

Asphaltenes, the most aromatic of the heaviest components of crude oil, are critical to all aspects of petroleum use, including production, transportation, refining, upgrading, and heavy-end use in paving and coating materials. As such, efficiency in these diverse disciplines mandates proper chemical accounting of structure−function relations of crude oils and asphaltenes, the vision of petroleomics (Asphaltenes, Heavy Oils and Petroleomics; Mullins, O. C., Sheu, E. Y., Hammami, A., Marshall, A. G., Eds.; Springer: New York, 2007). Indeed, the molecular characterization of asphaltenes is required as well as the detailed understanding of the hierarchical colloidal structures of asphaltenes and petroleum. With great prescience, Professor Teh Fu Yen and co-workers proposed a hierarchical model of asphaltenes to account for many of their characteristics known at that time (Dickie, J. P.; Yen, T. F. Macrostrucutres of asphaltic fractions by various instrumental methods. Anal. Chem. 1967, 39, 1847−1852). This m...

The Modified Yen Model

Our current understanding of water-in-crude oil emulsions. - Recent characterization techniques and high pressure performance

Asphaltene adsorption at solid surfaces is a ubiquitous phenomenon that begins within the production well and continues through the entire production chain. It is generally an undesirable phenomenon that causes damage within reservoirs, fouling of pipelines and transportation equipment, and fouling of refining and upgrading equipment. However, by virtue of this phenomenon, problematic asphaltenes may also be selectively removed from petroleum streams to produce partially upgraded petroleum, which has significantly improved handling, processing, and upgrading qualities. This review covers many basic aspects regarding the chemical and physical nature of asphaltenes and sorbents related to asphaltene adsorption.

Asphaltene Adsorption, a Literature Review

Corrosion and corrosion control

Heavy oil molecular mixtures were investigated on the basis of single molecules resolved by atomic force microscopy. The eight different samples analyzed include asphaltenes and other heavy oil fractions of different geographic/geologic origin and processing steps applied. The collected AFM data of individual molecules provide information about the molecular geometry, aromaticity, the content of nonhexagonal rings, typical types and locations of heterocycles, occurrence, length and connectivity of alkyl side chains, and ratio of archipelago- vs island-type architectures. Common and distinguishing structural motifs for the different samples could be identified. The measured size distributions and the degree of unsaturation by scanning probe microscopy is consistent with mass spectrometry data presented herein. The results obtained reveal the complexity, properties and specifics of heavy oil fractions with implications for upstream oil production and downstream oil processing. Moreover, the identified molec...

Heavy Oil Based Mixtures of Different Origins and Treatments Studied by Atomic Force Microscopy

The influence of different factors on the asphaltene stability in four crude oils was evaluated. Compositional studies and structural characterization of resins and asphaltenes were carried out in order to study a possible relationship between these properties and the asphaltene deposition behavior. Low hydrogen-to-carbon ratios, high aromaticities, and high condensation of aromatic rings were the main characteristics of the asphaltenes from unstable crude oils. According to these results, the stability behavior of the crude oils studied was strongly influenced by the structural characteristics of their asphaltenes. Since the self-aggregation of asphaltenes is a first step in the formation of precipitated asphaltene particles, this study also evaluates the formation of asphaltene aggregates as a function of the structural characteristics of the asphaltenes. The self-aggregation behavior was studied on the basis of surface tension measurements. Critical micelle concentrations were determined in different s...

Asphaltenes: Structural Characterization, Self-Association, and Stability Behavior

Molecular mechanics and dynamics calculations were carried out for asphaltenes and resins from crude oils of different origins. Average structural models were used in order to study the forces that determine the association process of asphaltenes and resins in crude oils. The stabilization energies obtained for asphaltene and resin associates were due mainly to the van der Waals forces between the molecules. Comparatively, the contribution of the hydrogen bonding to the stabilization energy was low. It was also found that few structural changes occur in the molecules due to aggregation. Therefore, the contribution of the conformation changes to the stabilization energy was also very low. According to the results obtained, the stabilization energy of the associates depends on the structural characteristics of the molecules. In particular, the stabilization energy is more favorable for those molecules with lower hydrogen-to-carbon ratio, higher aromaticity, and higher aromatic condensation degree. When diff...

Simulation of Interactions in Asphaltene Aggregates

Molecular dynamics simulations are carried out to estimate the density of average structures representative of various asphaltenes in an effort to evaluate the predictive capacities of this kind of structural models. Comparison between calculated and experimental values reveals that calculated densities are lower than experimental ones, but nevertheless calculated values show the correct tendency. This indicates that the chemical information provided by the average structures of asphaltenes is essentially correct and can be used to qualitatively estimate densities. On the basis of these results, the effect of different structural factors on calculated densities of asphaltenes was systematically studied. Large condensed aromatic rings and low hydrogen-to-carbon ratio are the main characteristics of the molecules which yield the highest densities. Also, it was found that a group-contribution method recently developed yields better density values than molecular dynamics simulations, although still lower than...

Density Estimation of Asphaltenes Using Molecular Dynamics Simulations

Adsorption isotherms of two native resins on two different asphaltene surfaces were obtained using the UV spectrophotometric technique. The shape of the curves obtained can be attributed both to multilayer adsorption and to penetration of resins in the microporous structure of the asphaltenes. The relationship between adsorption behavior and activity of the native resins as asphaltene stabilizers indicates that their effectiveness is related to their adsorbed amount on asphaltene particles and also to their capacity to dissolve asphaltenes. The results obtained support a model for asphaltene stabilization where the resins are incorporated into the bulk asphaltenes helping them to diffuse in the solvent. Significant differences in the behavior of native resins and alkylbenzene-derived amphiphiles as asphaltene stabilizers were observed. At the same equilibrium concentration, the adsorbed amount of native resins is lower than the adsorbed amount of amphiphiles. However, the native resins exhibit a higher as...

Estrella Rogel

Papers

Heavy Oil Based Mixtures of Different Origins and Treatments Studied by Atomic Force Microscopy

Asphaltenes: Structural Characterization, Self-Association, and Stability Behavior

Simulation of Interactions in Asphaltene Aggregates

Density Estimation of Asphaltenes Using Molecular Dynamics Simulations

Adsorption of Native Resins on Asphaltene Particles: A Correlation between Adsorption and Activity