Mass Spectrometric Advances in the Analysis of Large Aromatic Fractions of Heavy Fuel Oils and Carbon Particulates

Apicella, B.; Alfè, Michela; Ciajolo, A.

doi:10.1080/00102200903466335

Cited by 13 publications

(7 citation statements)

References 35 publications

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“…The relatively low laser power value (40% of its nominal value) used for LDI-TOFMS measurements so far described was chosen in order to limit the fragmentation occurrence due to high laser power. Indeed, the almost complete absence of fragmentation is confirmed by the similarity of the LDI-TOFMS spectrum distribution (Figure 1) with the mass spectrum reported in Figure 4, which has been obtained on the same asphaltene sample with a softer ionization method, namely atmospheric pressure photoionization (APPI) [25]. Therefore, the chosen laser power represents a good compromise between asphaltene volatility and fragmentation [26].…”

Section: Resultssupporting

confidence: 62%

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Characterization Techniques Coupled with Mathematical Tools for Deepening Asphaltene Structure

Apicella¹,

Ciajolo²,

Carpentieri

et al. 2022

Fuels

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Asphaltenes are the heavy fraction of fossil fuels, whose characterization remains a very difficult and challenging issue due to the still-persisting uncertainties about their structure and/or composition and molecular weight. Asphaltene components are highly condensed aromatic molecules having some heteroatoms and aliphatic functionalities. Their molecular weights distribution spans in a wide range, from hundreds to millions of mass units, depending on the diagnostic used, which is mainly due to the occurrence of self-aggregation. In the present work, mass spectrometry along with size exclusion chromatography and X-ray diffraction analysis have been applied to asphaltenes for giving some further insights into their molecular weight distribution and structural characteristics. Relatively small polycyclic aromatic hydrocarbons (PAHs) with a significant degree of aliphaticity were individuated by applying fast Fourier transform (FFT) and double bond equivalent (DBE) number analysis to the mass spectra. X-ray diffraction (XRD) confirmed some aliphaticity, showing peaks specific of aliphatic functionalities. Size exclusion chromatography indicated higher molecular weight, probably due to the aliphatic substituents. Mass spectrometry at high laser power enabled observing a downward shift of molecular masses corresponding to the loss of about 10 carbon atoms, suggesting the occurrence of aryl-linked core structures assumed to feature asphaltenes along with island and archipelago structures.

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Section: Resultssupporting

confidence: 62%

“…Figure 4. Atmospheric pressure photoionization mass spectrometry (APPI-MS) spectrum of asphaltenes (adapted from[25]). …”

mentioning

confidence: 99%

Characterization Techniques Coupled with Mathematical Tools for Deepening Asphaltene Structure

Apicella¹,

Ciajolo²,

Carpentieri

et al. 2022

Fuels

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“…The charm of this method is that it simplifies the sample preparation and also avoids possible interferences from MALDI matrix‐derived background ions. LDI‐MS has been applied to study the presence of polyaromatics in solid samples and extracts from different environments, in which, next to using one laser for concomitant desorption/ionization, the use of a two‐laser scheme for desorption and succeeding postionization has also been reported …”

Section: Introductionmentioning

confidence: 99%

Ultraviolet laser desorption/ionization mass spectrometry of single-core and multi-core polyaromatic hydrocarbons under variable conditions of collisional cooling: insights into the generation of molecular ions, fragments and oligomers

et al. 2014

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The ultraviolet laser desorption/ionization of polyaromatic hydrocarbons (PAHs) has been investigated under different background pressures of an inert gas (up to 1.2 mbar of N2) in the ion source of a hybrid, orthogonal-extracting time-of-flight mass spectrometer (oTOF-MS). The study includes an ensemble of six model PAHs with isolated single polyaromatic cores and four ones with multiple cross-linked aromatic and polyaromatic cores. In combination with a weak ion extraction field, the variation of the buffer gas pressure allowed to control the degree of collisional cooling of the desorbed PAHs and, thus, to modulate their decomposition into fragments. The dominant fragmentation channels observed are related to dehydrogenation of the PAHs, in most cases through the cleavage of even numbers of C-H bonds. Breakage of C-C bonds leading to the fragmentation of rings, side chains and core linkages is also observed, in particular, at low buffer gas pressures. The precise patterns of the combined fragmentation processes vary significantly between the PAHs. The highest abundances of molecular PAH ions and cleanest mass spectra were consistently obtained at the highest buffer gas pressure of 1.2 mbar. The effective quenching of the fragmentation pathways at this elevated pressure improves the sensitivity and data interpretation for analytical applications, although the fragmentation of side chains and of bonds between (poly)aromatic cores is not completely suppressed in all cases. Moreover, these results suggest that the detected fragments are generated through thermal equilibrium processes rather than as a result of rapid photolysis. This assumption is further corroborated by a laser desorption/ionization post-source decay analysis using an axial time-of-flight MS. In line with these findings, covalent oligomers of the PAHs, which are presumably formed by association of two or more dehydrogenated fragments, are detected with higher abundances at the lower buffer gas pressures.

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“…Because of their technological relevance, much effort has been devoted to characterize the molecular structure of the complex and broad range of polar and nonpolar compounds encompassed by such a phenomenological definition. , Modern mass spectrometry (MS) techniques have contributed crucially to the understanding of the structural and physicochemical properties of asphaltenes. Ultra-high-resolution Fourier transform ion cyclotron resonance (FT−ICR) measurements have identified the stoichiometry of thousands of polar compounds produced by different vaporization and ionization techniques. − The FT−ICR experiments are in concordance with systematic MS studies based on atmospheric pressure ionization, − field desorption, ,, and laser desorption/ionization (LDI). ,,− …”

Section: Introductionmentioning

confidence: 85%

One- and Two-Step Ultraviolet and Infrared Laser Desorption Ionization Mass Spectrometry of Asphaltenes

Hurtado¹,

Gámez²,

Martínez–Haya³

2010

Energy Fuels

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The determination of reliable molecular-weight distributions of complex asphaltene fractions has challenged modern mass spectrometry. This investigation extends previous studies on the application in this field of one-step laser desorption/ionization (LDI) and two-step laser desorption/post-ionization (L2MS) techniques employing ultraviolet (UV) and mid-infrared (IR) wavelengths. In the LDI experiments, single-resonant UV (280 nm) or IR (3.45 μm) laser pulses are applied for desorption−ionization of a model asphaltene sample. In the L2MS approach, asphaltene neutrals are postionized in the gas phase by a high power UV (266 nm) laser pulse. The study confirms that one-step UV−LDI easily induces aggregation of the asphaltenes. In contrast, in one-step IR−LDI and two-step UV/UV−L2MS and IR/UV−L2MS, aggregation is largely suppressed and the measurements reproduce correctly the known molecular-weight distribution of the model asphaltenes, with a bulk of constituents within m/z 200−1000. It is shown that the two-step methods also provide valuable information about the dynamics of the laser desorption process.

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Mass Spectrometric Advances in the Analysis of Large Aromatic Fractions of Heavy Fuel Oils and Carbon Particulates

Cited by 13 publications

References 35 publications

Characterization Techniques Coupled with Mathematical Tools for Deepening Asphaltene Structure

Characterization Techniques Coupled with Mathematical Tools for Deepening Asphaltene Structure

Ultraviolet laser desorption/ionization mass spectrometry of single-core and multi-core polyaromatic hydrocarbons under variable conditions of collisional cooling: insights into the generation of molecular ions, fragments and oligomers

One- and Two-Step Ultraviolet and Infrared Laser Desorption Ionization Mass Spectrometry of Asphaltenes

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