Study on the structure and association of asphaltene derived from liquefaction of lignite by fluorescence spectroscopy

Wang, Zhicai; Hu, Jingchen; Shui, Hengfu; Ren, Shibiao; Wei, Cheng; Pan, Chunxiu; Lei, Zhiping; Cui, Xueping

doi:10.1016/j.fuel.2012.12.011

Cited by 29 publications

(10 citation statements)

References 29 publications

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“…For the lower concentration, the final configuration consisted of two-or three-molecule asphaltene aggregates, whereas for the 30.0 wt.% system, the final configuration consisted of three-and four-molecule aggregates. This indicates that for the mixture representation in n-heptane, the aggregate size increases with asphaltene concentration, as expected for asphaltenes in a paraffinic solvent [28], [29]. The growth of asphaltene aggregates is limited to a few molecules due to steric repulsion (four-molecule aggregates).…”

Section: Resultssupporting

confidence: 61%

Asphaltene Molecular Representation: Impact on Aggregation Evaluation

Velásquez¹,

Leon²,

Hoyos³

2017

World Congress on Mechanical, Chemical, and Material Engineering

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Molecular dynamics simulations were used to evaluate the effect of the asphaltene molecular representation on calculations of the aggregate size and aggregation behavior of asphaltene/solvent systems. Three different asphaltene representations were studied, namely, a mixture of four molecules, an island-type molecule and an archipelago-type molecule. Calculations were conducted for pure asphaltene systems and in solutions of n-heptane and toluene. For pure asphaltene systems, the island-type representation allows for the formation of extremely large aggregates, whereas for the mixture and archipelago representations, the aggregates contained up to four molecules. For asphaltene/solvent systems, the mixture representation was consistent with the expected solubility behavior of asphaltenes in both n-heptane and toluene. With this representation, the final configuration in n-heptane consisted of up to fourmolecule aggregates, whereas in toluene, the observed aggregates were dimers, at most. The structural configuration of the island-type molecule misrepresented the aggregation behavior of the asphaltenic phase. The representation of the asphaltene phase, exclusively with the archipelago architecture, also fails to correctly describe the asphaltene aggregation since almost no aggregation was observed. In n-heptane, the asphaltene aggregates were compact and stable with time, and their behavior resembled that of solid particles suspended in a fluid phase. In toluene, the aggregates were of a porous nature, forming viscoelastic networks and reducing the mobility of the fluid phase. The results indicate that the mixture representation is a more appropriate choice for the evaluation of asphaltenic system behavior.

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Section: Resultssupporting

confidence: 61%

Asphaltene Molecular Representation: Impact on Aggregation Evaluation

Velásquez¹,

Leon²,

Hoyos³

2017

World Congress on Mechanical, Chemical, and Material Engineering

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“…Different techniques have been developed to study the asphaltene molecular architecture. Whereas the archipelago molecular architecture has been confirmed using bulk decomposition techniques such as pyrolysis, Ruthenium Ion‐Catalyzed Oxidation (RICO) analyses, and fluorescence spectroscopy, the island architecture of asphaltene molecule has been revealed using techniques such as FD, Taylor Dispersion (TD), Molecular Orbital Calculations (MO), and FCS …”

Section: Asphaltene Molecular Structurementioning

confidence: 99%

A comprehensive study on mechanism of formation and techniques to diagnose asphaltene structure; molecular and aggregates: a review

Hosseini-Dastgerdi

Tabatabaei-Nejad

Khodapanah

et al. 2014

Asia-Pacific J Chem Eng

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As the formation of asphaltene aggregates causes its deposition in various processes, exact determination of the molecular and aggregate structure and mechanism of aggregate formation is very important in order to prevent asphaltene deposit formation. The aim of this paper is to review the molecular and aggregate structure of asphaltene using various techniques. The other purpose is to specify and compare different mechanisms of aggregate formation, suggested by researchers. These mechanisms are proposed by researchers according to the molecular characteristics of asphaltene and the structure of aggregates. Researchers have considered four general models for the formation mechanism of asphaltene aggregates: the micellar/colloidal, polymeric, solubility, and modified Yen models. In comparison with other models, the modified Yen model shows more consistency with new studies, which determine the island molecular structure and small nano-aggregates for asphaltene. Experimental studies show that the dominant mechanism of aggregate formation depends on asphaltene architecture, intermolecular forces, and the solubility definition of asphaltene. Depending on the asphaltene source, solvent, thermodynamic conditions, and various techniques such as near-infrared spectroscopy, nuclear magnetic resonance, small-angle neutron scattering, and small-angle X-ray scattering, different structural information on the shape (spheres, discoid, oblate, membrane-like, prolate cylinders, and mass fractal aggregates) and size of aggregates has been reported.

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“…UV-vis absorption spectrum is another valid way to determine asphaltene chromophore content aggregation degree [157] , interaction between asphaltenes and other compounds [158] , but usually in dilute solution with fluorescence spectrum [20,23,159] . Bigger aromatic nucleuses and molecular size would lead to lower UV-FL intensity [160] .…”

Section: Ultraviolet-visible (Uv-vis) Spectrometrymentioning

confidence: 99%