Conformational search and dimerization study of average structures of asphaltenes

Carauta, Alexandre Nelson Martiniano; Correia, Julio Cesar Guedes; Seidl, Peter Rudolf; Silva, Daniel M.

doi:10.1016/j.theochem.2005.02.063

Cited by 29 publications

(21 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…range of 1–10% lie within this range of linear dimensions and at the upper limit of the molecular weight range. However, the incompatibility of the high-concentration aggregation behavior with the Yen–Mullins hierarchy and the formation of a gel-like network connected by parallel stacked interactions run contrary to current understanding of asphaltene aggregation, wherein the Yen–Mullins model enjoys strong experimental ,,,− and computational ,,,,,− support and gelation is not experimentally observed until extremely high concentrations . Our results therefore lend support to the assertion that molecules possessing these archipelago structures and molecular weights in excess of ∼2000 g/mol are likely not present in appreciable quantities in naturally occurring crude oils. ,− …”

Section: Discussionsupporting

confidence: 73%

“…The Yen–Mullins model , (or modified Yen model) is a hierarchical model of asphaltene aggregation with broad experimental ,,,− and computational ,,,,,− support. Under the Yen–Mullins hierarchy, , asphaltenes are dispersed in crude oil as monomers and small oligomers at low concentrations (<100 mg/L), , form rodlike nanoaggregates of ∼10 molecules and linear extent ∼3 nm above the critical nanoaggregate concentration (CNAC) of ∼100 mg/L, − assemble into clusters of ∼10 nanoaggregates of extent ∼10 nm above the critical cluster concentration (CCC) of ∼5000 mg/L, and ultimately form a percolating network or micron-sized flocs at concentrations in excess of ∼50 000 mg/L. ,,− , …”

Section: Introductionmentioning

confidence: 99%

“…Molecular simulations have proved extremely valuable in resolving the atomic-level interactions and processes underpinning the Yen–Mullins assembly hierarchy. ,,,,,− This body of work has established generally consistent understanding of structural and thermodynamic behaviors undergirding assembly: the role of polyaromatic stacking in mediating the formation of nanoaggregate rods and offset and T-shaped stacking in the formation of clusters and the influence of temperature, pressure, and solvent composition in modulating assembly propensity. Notwithstanding these general principles, the molecular details of the asphaltene chemistry can strongly influence the particulars of the aggregation process.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Coarse-Grained Molecular Simulation and Nonlinear Manifold Learning of Archipelago Asphaltene Aggregation and Folding

2018

View full text Add to dashboard Cite

Asphaltenes constitute the heaviest aromatic component of crude oil. The myriad of asphaltene molecules falls largely into two conceptual classes: continental-possessing a single polyaromatic core-and archipelago-possessing multiple polyaromatic cores linked by alkyl chains. In this work, we study the influence of molecular architecture upon aggregation behavior and molecular folding of prototypical archipelago asphaltenes using coarse-grained molecular dynamics simulation and nonlinear manifold learning. The mechanistic details of aggregation depend sensitively on the molecular structure. Molecules possessing three polyaromatic cores show a higher aggregation propensity than those with two, and linear archipelago architectures more readily form a fractal network than ring topologies, although the resulting aggregates are more susceptible to disruption by chemical dispersants. The Yen-Mullins hierarchy of self-assembled aggregates is attenuated at high asphaltene mass fractions because of the dominance of promiscuous parallel stacking interactions within a percolating network rather than the formation of rodlike nanoaggregates and nanoaggregate clusters. The resulting spanning porous network possesses a fractal dimension of 1.0 on short length scales and 2.0 on long length scales regardless of the archipelago architecture. The incompatibility of the observed assembly behavior with the Yen-Mullins hierarchy lends support that high-molecular weight archipelago architectures do not occur at significant levels in natural crude oils. Low-dimensional free energy surfaces discovered by nonlinear dimensionality reduction reveal a rich diversity of metastable configurations and folding behavior reminiscent of protein folding and inform how intramolecular structures can be modulated by controlling asphaltene mass fraction and dispersant concentration.

show abstract

Section: Discussionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Coarse-Grained Molecular Simulation and Nonlinear Manifold Learning of Archipelago Asphaltene Aggregation and Folding

2018

View full text Add to dashboard Cite

show abstract

“…In another study [76] based on MM and semiempirical calculations, the interaction energy was reported to be À45 kcal/mol for two asphaltene dimers, each containing a hydroxyl group. A small percentage of the difference between DFT results and MM results could be attributed to the removal of aliphatic side chains in our calculations, and a portion of the difference may be caused by the inadequacy of the level of calculations based on COMPASS Force Field parameters.…”

Section: Diagonalmentioning

confidence: 99%

The influence of asphaltene-resin molecular interactions on the colloidal stability of crude oil

Mousavi

Abdollahi

Pahlavan

et al. 2016

Fuel

137

View full text Add to dashboard Cite

g r a p h i c a l a b s t r a c t Micellar structure of asphaltene in a dispersing medium of lighter resins, aromatics, and saturates. a b s t r a c tIn the colloidal hypothesis of vacuum residua and asphalt, micelles are assumed to have an asphaltenic core with the greatest weight and aromaticity and an outer shell composed of lighter and less aromatic molecules. The true nature of the micelles, and the asphaltenic core in particular, has always been a debatable issue among asphalt researchers. One of the frequently asked questions is whether asphaltenes exist as stacked layers within the micelles or as single molecular units stabilized by resin molecules. In this paper, we investigate the correlation between the number of asphaltene sheets and the final stability of the system in a medium of asphaltene and resin components. Our evaluation is based on rigorous quantum mechanical calculations using a DFT-D approach. Our quantitative findings corroborate the view that the colloidal behavior of crude oil is better described by asphaltene-asphaltene associations. Moreover, our calculations show that if both asphaltene and resin are present, resin-asphaltene interactions are preferred over asphaltene-asphaltene interactions only if the number of resin molecules per micelle is greater than the number of asphaltene molecules per micelle.

show abstract

“…Asphaltene aggregation is largely driven by the π–π and π–σ interaction between the electron clouds of the polyaromatic cores. ,,, Aggregation proceeds by a hierarchical self-assembly process described by the Yen–Mullins model. ,,,,,− At low concentrations (<100 mg/L), asphaltene molecules are dispersed as monomers and small oligomers. , As concentration is elevated, the asphaltenes first begin to form rod-like nanoaggregates comprising ∼10 molecules (>100 mg/L) (stage I), followed by clusters of nanoaggregates (>5000 mg/L) (stage II), and finally a fractal network or large floc-like precipitates (>50,000 mg/L) (stage III). ,,− A number of experimental ,,,,− and computational ,,,,,,− studies support the Yen–Mullins model, revealing the fundamental role of π–π and π–σ interactions in driving core–core stacking in the nanoaggregates and nanoaggregate clusters, the importance of nonspecific dispersion interactions between aliphatic side chains in limiting nanoaggregate size and mediating the formation of the percolating fractal network, and a reduced propensity for aggregate formation in toluene relative to n -heptane.…”

Section: Introductionmentioning

confidence: 99%

Mesoscale Simulation and Machine Learning of Asphaltene Aggregation Phase Behavior and Molecular Assembly Landscapes

2017

View full text Add to dashboard Cite

Asphaltenes constitute the heaviest fraction of the aromatic group in crude oil. Aggregation and precipitation of asphaltenes during petroleum processing costs the petroleum industry billions of dollars each year due to downtime and production inefficiencies. Asphaltene aggregation proceeds via a hierarchical self-assembly process that is well-described by the Yen-Mullins model. Nevertheless, the microscopic details of the emergent cluster morphologies and their relative stability under different processing conditions remain poorly understood. We perform coarse-grained molecular dynamics simulations of a prototypical asphaltene molecule to establish a phase diagram mapping the self-assembled morphologies as a function of temperature, pressure, and n-heptane:toluene solvent ratio informing how to control asphaltene aggregation by regulating external processing conditions. We then combine our simulations with graph matching and nonlinear manifold learning to determine low-dimensional free energy surfaces governing asphaltene self-assembly. In doing so, we introduce a variant of diffusion maps designed to handle data sets with large local density variations, and report the first application of many-body diffusion maps to molecular self-assembly to recover a pseudo-1D free energy landscape. Increasing pressure only weakly affects the landscape, serving only to destabilize the largest aggregates. Increasing temperature and toluene solvent fraction stabilizes small cluster sizes and loose bonding arrangements. Although the underlying molecular mechanisms differ, the strikingly similar effect of these variables on the free energy landscape suggests that toluene acts upon asphaltene self-assembly as an effective temperature.

show abstract

Conformational search and dimerization study of average structures of asphaltenes

Cited by 29 publications

References 18 publications

Coarse-Grained Molecular Simulation and Nonlinear Manifold Learning of Archipelago Asphaltene Aggregation and Folding

Coarse-Grained Molecular Simulation and Nonlinear Manifold Learning of Archipelago Asphaltene Aggregation and Folding

The influence of asphaltene-resin molecular interactions on the colloidal stability of crude oil

Mesoscale Simulation and Machine Learning of Asphaltene Aggregation Phase Behavior and Molecular Assembly Landscapes

Contact Info

Product

Resources

About