Solid Petroleum Asphaltenes Seem Surrounded by Alkyl Layers

Carbognani, Lante; Rogel, Estrella

doi:10.1081/lft-120018537

Cited by 20 publications

(20 citation statements)

References 31 publications

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Section: Introductionsupporting

confidence: 92%

“…The authors observed similar trends for the parent whole crude oil, thereby suggesting that interactions between aliphatic moieties could be central in petroleum and asphaltene aggregation. These results are consistent with the idea that London forces between alkyl side chains drive the self-assembly of asphaltene nanoaggregates to produce more massive clusters, widely reported by Rogel, 64 Carbognani, 65 and Stachowiak et al 66 It is critical to point out that there is not a clear correlation between asphaltene aggregation in industrial applications (e.g., fouling in production facilities) and GPC elution trends. For example, Muller et al 67,68 fractionated geologically diverse crude oils by GPC and used off-line FT-ICR MS for molecular characterization.…”

Section: ■ Introductionsupporting

confidence: 88%

See 1 more Smart Citation

Compositional Trends for Total Vanadium Content and Vanadyl Porphyrins in Gel Permeation Chromatography Fractions Reveal Correlations between Asphaltene Aggregation and Ion Production Efficiency in Atmospheric Pressure Photoionization

et al. 2020

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Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has exposed the ultracomplexity of fossil fuels, thereby validating the compositional trends that rule petroleum distillation, known as the Boduszynski Continuum. Routine FT-ICR MS analysis of a single crude oil sample can reveal tens-of-thousands of unique molecular formulas; however, currently available ionization methods suffer from limitations for such complex mixtures that are not yet completely understood. Simply put, MS detects ions, and thus, it depends heavily on the ability of ion sources to indiscriminately volatilize and subsequently ionize samples of interest. Despite advances in soft ionization methods, the characterization of complex matrices remains a challenge due to the lack of an ion source, commercial or custom-built, that can vaporize and ionize all compounds without bias, save analyte concentration. However, atmospheric pressure photoionization (APPI) has been shown to provide the most uniform ion production for mixtures of petroleum model compounds and real samples, with little to no fragmentation. In this work, we investigated the molecular composition of PetroPhase 2017 asphaltenes and its extrography fractions, with a focus on the total vanadium content and molecular composition of vanadyl porphyrins as a function of aggregate size distribution, accessed through separate experiments: online gel permeation chromatography (GPC) inductively coupled plasma−MS (ICP−MS) and online GPC APPI FT-ICR MS (at 21 T). The results reveal that the extrography separation provides asphaltene fractions (i.e., acetone, Hep/Tol, and Tol/THF/MeOH) enriched in 51 V-containing compounds with distinctive aggregate size distributions. The acetone fraction features smaller aggregate sizes, as it elutes later in the GPC chromatogram than Hep/Tol and Tol/THF/MeOH fractions, and overall, presents up to ∼14-fold higher ionization efficiency in APPI. Such behavior suggests a correlation between aggregate size and production efficiency of monomeric ions in APPI. Bulk compositional trends accessed by GPC separation and highlighted by ICP−MS detection indicate that despite multiple separation steps (i.e. extrography followed by GPC), APPI FT-ICR MS can only access ∼37% of the total V-containing compounds. Although the more stable/larger aggregates dominate the size distributions of all asphaltene samples studied, it is the weakly aggregated/monomeric species that are preferentially observed by APPI-MS. Tendencies in the molecular composition of vanadyl porphyrins and S/O-containing compounds strongly suggest that London forces might be central in the self-assembly process of asphaltene nanoaggregates to produce more massive clusters. The results demonstrate that the observed compositional trends (albeit limited) can be accessed when coupling advanced chromatographic separations with online high-field FT-ICR MS detection.

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Section: Introductionsupporting

confidence: 92%

Section: ■ Introductionsupporting

confidence: 88%

Compositional Trends for Total Vanadium Content and Vanadyl Porphyrins in Gel Permeation Chromatography Fractions Reveal Correlations between Asphaltene Aggregation and Ion Production Efficiency in Atmospheric Pressure Photoionization

et al. 2020

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“…GPC FT-ICR MS results are consistent with several works that suggest that London forces between aliphatic moieties might be central in asphaltene aggregation. − For instance, the self-aggregation nature of model asphaltene compounds, with varying content of aliphatic chains and heteroatomic functionalities, was tested by molecular dynamics simulations . The authors observed a direct correlation between increased dissociation energy and higher contents of aliphatic chains and heteroatoms.…”

Section: A Comprehensive Analytical Approach To Understand Ultracompl...supporting

confidence: 85%

Lessons Learned from a Decade-Long Assessment of Asphaltenes by Ultrahigh-Resolution Mass Spectrometry and Implications for Complex Mixture Analysis

et al. 2021

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Recent advances in instrumentation for high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) have enabled access to ∼70 000 unique molecular formulas in broadband mass spectral characterization of unfractionated/whole asphaltenes. The results accumulated over a decade highlight the need for an asphaltene molecular model that acknowledges the coexistence of (1) monofunctional and polyfunctional species; (2) island and archipelago structural motifs; and (3) heteroatom-depleted/highly aromatic compounds, as well as atypical species with low aromaticity but increased heteroatom content. Collectively, results from FT-ICR MS, preparatory-scale separations (extrography/interfacial material), gel permeation chromatography, precipitation behavior in heptane:toluene, thermal decomposition, and aggregate microstructure by atomic force microscopy (among other techniques), suggest that the strong aggregation of asphaltenes results from the synergy between several intermolecular forces: π-stacking, hydrogen bonding, London forces, and acid/base interactions. This review presents general features of asphaltene molecular composition reported over the past five decades. We focus on mass spectrometry characterization and expose the reasons why early results supported the dominance of single-core motifs. Then, the discussion shifts to recent advances in instrumentation for high-field FT-ICR MS, which have enabled the detection of thousands of species in asphaltene samples, whose molecular composition and fragmentation behavior in ultrahigh vacuum agree with the coexistence of single-core and multicore structural motifs. Furthermore, evidence that highlights the limitations of commercially available/custom-built ion sources and selective ionization effects is presented. Consequently, the limitations require separations (e.g., chromatography, extrography) to gain more-comprehensive molecular-level insights into the composition of these complex organic mixtures. The final sections present evidence for the role of aggregation in selective ionization and suggest that advanced characterization by both thermal desorption/decomposition and liquid chromatography with online FT-ICR MS detection can be employed to mitigate the effects of aggregation and provide unique insights in molecular composition/structure.

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“…Carbognani and Rogel realized a study of dissolution kinetics for wax in toluene at 25 °C using pure asphaltenes and complex mixtures formed for these fractions, to observe the interaction among each other. The authors found that the unstable asphaltenes have proved to be highly aromatic and devoid of alkyl appendages.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Effect of Chemical Structure of Asphaltenes on Wax Crystallization of Crude Oils from Colorado Oil Field

2017

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the structural differences of asphaltenes in Colombian light crude oils from the same field, i.e., the Colorado oilfield, were presented. Colorado crude oil is a light crude with very low content of asphaltenes (<0.3%, w/w) and presents paraffin crystallization problems during its production. In the parafinic deposits, asphaltenes have also been found. In this work, a new methodology is proposed to determine the effects of chemical structure and concentration of asphaltenes on the wax crystallization of the crude oils from the Colorado oilfield. Six crude oils (from different sands) were fractionated in their respective asphaltenes and maltenes. The crystallization properties of crude oils and maltenes were obtained: wax appearance temperature (WAT), pour point, and crystallization enthalpy. Asphaltenes were characterized by nuclear magnetic resonance analysis, mass spectrometry, X-ray diffraction, and Raman spectroscopy, and their main average molecular parameters (AMPs) were calculated. Partial least-squares regression (PLS) analysis was used to understand the influence of asphaltenes chemical structure on the crystallization processes. The proposed characterization−statistical analysis methodology allowed for the understanding of the effect of the average molecular structure of asphaltenes on the crystallization properties of paraffins from the crude oils of the Colorado field. The effect of asphaltenes was analyzed through correlation between the differences in WAT, the differences in pour poin,t and the relative crystallization (C r ) with the AMPs of asphaltenes. The AMPs of the asphaltenes causing the greatest impact on the increase of the crystallization temperature are the pericondensed carbons (C aaa ), ratio of peripheral carbons/aromatic carbons (C p /C ar ), and aromaticity factor ( f a ), and decreases in these properties are attributed to the length of the aliphatic chains (n) and the naphthenic rings (C n ); the concentration of asphaltenes (C oasf ) has little effect. The degree of crystallization is increased by f a and decreased with C aaa , C p /C ar , paraffinic carbons (C s ), and C oasf . The pour point is only increased by f a and decreased withC aaa and C n , and C oasf is negligible.

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Solid Petroleum Asphaltenes Seem Surrounded by Alkyl Layers

Cited by 20 publications

References 31 publications

Compositional Trends for Total Vanadium Content and Vanadyl Porphyrins in Gel Permeation Chromatography Fractions Reveal Correlations between Asphaltene Aggregation and Ion Production Efficiency in Atmospheric Pressure Photoionization

Compositional Trends for Total Vanadium Content and Vanadyl Porphyrins in Gel Permeation Chromatography Fractions Reveal Correlations between Asphaltene Aggregation and Ion Production Efficiency in Atmospheric Pressure Photoionization

Lessons Learned from a Decade-Long Assessment of Asphaltenes by Ultrahigh-Resolution Mass Spectrometry and Implications for Complex Mixture Analysis

Understanding the Effect of Chemical Structure of Asphaltenes on Wax Crystallization of Crude Oils from Colorado Oil Field

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