Size and shape of a coal asphaltene studied by viscosity and diffusion coefficient measurements

Wargadalam, Verina J.; Norinaga, Koyo; Iino, Masashi

doi:10.1016/s0016-2361(02)00055-8

Cited by 95 publications

(99 citation statements)

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“…TD was used by Iino and co-workers at Tohoku University. 57 In this technique, an initial perpendicular plane of asphaltene solution is prepared in a capillary. Laminar flow is initiated.…”

Section: Molecular Diffusionmentioning

confidence: 99%

“…As made clear by those authors in their paper, TD results agree exactly with those from TRFD for the exact same asphaltene samples. 57 Translation diffusion based on NMR pulsed field gradient techniques has been employed by Freed and co-workers. 27 Translational diffusion of molecules in a field gradient gives rise to local out-of-phase spins thereby reducing echo amplitude.…”

Section: Molecular Diffusionmentioning

confidence: 99%

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Contrasting Perspective on Asphaltene Molecular Weight. This Comment vs the Overview of A. A. Herod, K. D. Bartle, and R. Kandiyoti

2008

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Asphaltene molecular weight (Asphaltenes, HeaVy Oils and Petroleomics; Springer: New York, 2007) continues to be the subject of a longstanding debate in the literature. A paper (Energy Fuels 2007, 21, 2176-2203 recently published (referred to as HBK) claims that asphaltene molecular weights are bimodal with one component in the roughly megadalton range and a second component in the roughly 5 kDa range. These claims are in sharp contrast to results published from a variety of measurements with the overall conclusions that asphaltene molecular weights are monomodal with a most probable 750 Da ((200) with a fwhm 500-1000 Da. In this report, we provide a summary of the four molecular diffusion techniques and seven mass spectral techniques from many groups around the world that are all in accord with the 750 Da most probable mass. Moreover, here we discuss why HBK reported anomalously large asphaltene molecular weights along with the unique claim of a bimodal distribution. In particular, the size exclusion chromatography (SEC) results that yield megadalton masses were performed with the solvent N-methylpyrrolidinone which is known to flocculate up to 50% of the asphaltenes. The megadalton mass is likely large asphaltene aggregates or flocs. In a previous referenced paper from the HBK labs, the better solvent for asphaltenes, tetrahydrofuran, did not give the megadalton peak in their SEC experiments as they stated; we suspect because the asphaltenes were suitably dissolved (although still with some aggregation). The corresponding discussion treats the known hierarchy of asphaltene aggregation at very low concentration in a good solvent, toluene. In addition, the mass spectral method used in HBK, laser desorption ionization, is shown herein and in the literature to yield anomalously large molecular weights for asphaltenes and polycyclic aromatic hydrocarbons due to gas phase aggregation if (1) the laser power is too high, (2) the surface concentration of asphaltenes is too high, or (3) if the ions are collected too quickly (i.e., from a dense plasma). Properly accounting for these potential pitfalls, one obtains the same most probable 750 Da molecular weight as from all of the other techniques. Finally, ESI MS is shown herein and in ample literature to be readily able to detect large masses (the primary reason ESI led to a Nobel Prize); the absence of large mass species in ESI MS of asphaltenes is because they are not present. The congruence of so many molecular diffusion techniques and mass spectral techniques is a powerful advance for asphaltene science.

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“…TD was used by Iino and co-workers at Tohoku University. 57 In this technique, an initial perpendicular plane of asphaltene solution is prepared in a capillary. Laminar flow is initiated.…”

Section: Molecular Diffusionmentioning

confidence: 99%

Section: Molecular Diffusionmentioning

confidence: 99%

Contrasting Perspective on Asphaltene Molecular Weight. This Comment vs the Overview of A. A. Herod, K. D. Bartle, and R. Kandiyoti

2008

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“…The structures of asphaltenes are formed by polyaromatic cores attached to aliphatic chains containing heteroatoms, such as nitrogen, oxygen, sulfur, and metals including vanadium, iron, and nickel (Chianelli et al 2007;Mullins et al 2012;Mullins 2011;Mullins 1999, 2000). Asphaltenes also contain polar and nonpolar groups and tend to form i-mer colloids due to their polarizability and self-associative characteristics Bockrath et al 1980;Wargadalam et al 2002;Rosales et al 2006;Acevedo et al 1998;Mousavi-Dehghani et al 2004;Sheu et al 1994). It has been widely documented that the viscosity of heavy oil can dramatically increase due to asphaltene aggregation (Acevedo et al 1998;Mousavi-Dehghani et al 2004;Sheu et al 1994).…”

Section: Introductionmentioning

confidence: 99%

Kinetics and mechanisms of the catalytic thermal cracking of asphaltenes adsorbed on supported nanoparticles

et al. 2016

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The production of heavy and extra-heavy oil is challenging because of the rheological properties that crude oil presents due to its high asphaltene content. The upgrading and recovery processes of these unconventional oils are typically water and energy intensive, which makes such processes costly and environmentally unfriendly. Nanoparticle catalysts could be used to enhance the upgrading and recovery of heavy oil under both in situ and ex situ conditions. In this study, the effect of the Ni-Pd nanocatalysts supported on fumed silica nanoparticles on post-adsorption catalytic thermal cracking of n-C 7 asphaltenes was investigated using a thermogravimetric analyzer coupled with FTIR. The performance of catalytic thermal cracking of n-C 7 asphaltenes in the presence of NiO and PdO supported on fumed silica nanoparticles was better than on the fumed silica support alone. For a fixed amount of adsorbed n-C 7 asphaltenes (0.2 mg/m 2 ), bimetallic nanoparticles showed better catalytic behavior than monometallic nanoparticles, confirming their synergistic effects. The corrected OzawaFlynn-Wall equation (OFW) was used to estimate the effective activation energies of the catalytic process. The mechanism function, kinetic parameters, and transition state thermodynamic functions for the thermal cracking process of n-C 7 asphaltenes in the presence and absence of nanoparticles are investigated.

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“…Recently, a study was conducted on the development of a spectroscopic method for the quantiication of functional groups characteristic of asphaltenes, making direct quantiication from oil a direct and practical method [24]. Nondiluted light and heavy crude oils and their blends were studied with additives of pyrolysis oil and Kemelix, both acting as asphaltene dispersants [25].…”

Section: Types Of Characterizations For Crude Oil and Asphaltenesmentioning

confidence: 99%

Characterization of Crude Oils and the Precipitated Asphaltenes Fraction using UV Spectroscopy, Dynamic Light Scattering and Microscopy

Cruz¹,

Rivas²,

García³

et al. 2018

Recent Insights in Petroleum Science and Engineering

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Analysis of crude oil composition provides important information that impacts on the recovery, handling, and transportation of hydrocarbons. Crude characterization also provides data in the analysis of geochemistry of the source of origin. Crude oil characterization by optical methods is usually diicult because of its dark color; however, those characterizations are crucial because they give information that can afect some analysis procedures. Ultraviolet-visible (UV-vis) spectroscopy is a simple and practical technique that allows the characterization of crude oil through dilution in solvents. A comparative study of crude oil solutions contrasted with their asphaltene fractions was performed. Each solution was analyzed in triplicate, on a UV-vis spectrophotometer. Calibration curves for both raw solutions showed no signiicant variations, indicating stability. Additionally, the results of dispersion and migration phenomena indicated stability only for crude oil solutions. The aggregate size dispersion was diferent for each type of crude and varied with respect to time. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the type of morphology present for each type of asphaltene.

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Size and shape of a coal asphaltene studied by viscosity and diffusion coefficient measurements

Cited by 95 publications

References 11 publications

Contrasting Perspective on Asphaltene Molecular Weight. This Comment vs the Overview of A. A. Herod, K. D. Bartle, and R. Kandiyoti

Contrasting Perspective on Asphaltene Molecular Weight. This Comment vs the Overview of A. A. Herod, K. D. Bartle, and R. Kandiyoti

Kinetics and mechanisms of the catalytic thermal cracking of asphaltenes adsorbed on supported nanoparticles

Characterization of Crude Oils and the Precipitated Asphaltenes Fraction using UV Spectroscopy, Dynamic Light Scattering and Microscopy

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