Fractal dimension of asphaltene aggregates determined by turbidity

Gmachowski, Lech; Paczuski, M.

doi:10.1016/j.colsurfa.2011.05.007

Cited by 15 publications

(15 citation statements)

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“…Experimental work has established the fractal dimension of the spanning networks formed at high asphaltene m.f.’s to lie in the range 1.3–2.0. − We have previously used the correlation dimension as a means to estimate the fractal dimensionality of self-assembled spanning networks of continental asphaltenes ,− and employ it here to study archipelago architectures. Given a particular system configuration extracted from our simulation trajectory, we define the correlation sum between polyaromatic cores as where N is the number of polyaromatic cores in our simulation snapshot, r ij COM is the center of mass distance between polyaromatic cores i and j , H is Heaviside step function, and ϵ is a tunable cutoff distance.…”

Section: Resultsmentioning

confidence: 99%

“…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%

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

2018

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2018

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“…Liu et al [141] and Barré et al [142] found aggregates having a fractal-like structure in concentrated ASP suspensions in n-heptane. By using the photon correlation spectroscopy technique, it has been found that ASP flocs can reach sizes in the range of 4-5 µm when ultimate sedimentation occurs [143], and this phenomenon is corroborated by fractal-like diffusion-limited aggregation [144][145][146][147].…”

Section: Scattering Techniques and Fractal Nature Of Bitumen Microsct...mentioning

confidence: 93%

The Structure of Bitumen: Conceptual Models and Experimental Evidences

et al. 2022

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Bitumen, one of the by-products of petroleum industry processes, is the most common binder used in road pavements and in the construction industry in general. It is a complex organic mixture of a broad range of hydrocarbons classified into four chemical families, collectively known with the acronym SARA fractions, which include saturates, aromatics, resins and asphaltenes. Since the 1940s, researchers working on bitumen and the science behind its existence, nature and application have investigated the spatial organization and arrangement of several molecular species present in the binder. Therefore, several models have been proposed in the literature, and they are more or less corroborated by experimental studies, although most of them are model-dependent; for example, the structural investigations based on scattering techniques. One of the most popular models that has met with a wide consensus (both experimentally and of the modeling/computational type) is the one aiming at the colloidal description of bitumen’s microstructure. Other types of models have appeared in the literature that propose alternative views to the colloidal scheme, equally valid and capable of providing results that comply with experimental and theoretical evidence. Spurred by the constant advancement of research in the field of bitumen science, this literature review is aimed at providing a thorough, continuous and adept state of knowledge on the modeling efforts herein elaborated, in order to more precisely describe the intricacy of the bituminous microstructure. In this body of work, experimental evidence, along with details of bitumen’s microstructure (depicting the colloidal state of bitumen), is particularly emphasized. We will also try to shed light on the evolution of the experimental and theoretical results that have focused on the aspect of the association and aggregation properties of asphaltenes in various models and real systems.

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“…The aggregate of mixed statistics can be obtained by shearing the crude oil (Gmachowski & Paczuski, 2011). Asphaltenes, a part of petroleum, are aromatic multicyclic molecules surrounded and linked by aliphatic chains and heteroatoms, of the molar mass in the range 500-50000 u.…”

Section: Asphaltene Aggregatesmentioning

confidence: 99%

“…Lech Gmachowski (2011). Hydrodynamic Properties of Aggregates with Complex Structure, HydrodynamicsAdvanced Topics, Prof. Harry Schulz (Ed.…”

Section: How To Referencementioning

confidence: 99%