In this contribution, we use high-resolution mass spectrometry to unveil the molecular composition of occluded compounds inside Colombian asphaltenes macrostructures. We use Soxhlet extraction, with n-heptane, coupled with asphaltene maceration to obtain four fractions enriched with chemical compounds occluded inside asphaltene networks. We focused our efforts on the fraction enriched with compounds interacting with asphaltenes via strong intermolecular forces, and used normal phase column chromatography to fractionate it and atmospheric pressure photoionization coupled to Fourier transform ion cyclotron resonance mass spectrometry to obtain a detailed molecular description. Our results indicate that the occluded compounds obtained in the last stage of the washing process are by themselves a complex mixture, consisting mostly of saturated compounds including molecular formulas corresponding to biomarkers, alkyl aromatics with high heteroatom content (up to four heteroatoms), vanadyl porphyrins, and highly aromatic species, which we believe are low-molecular weight asphaltenes transferred to the n-heptane during the extraction process. We consider this information valuable because analysis of occluded compounds gives us a more thorough molecular description of asphaltenes; besides, knowledge of compounds closely related to asphaltenes could not only improve deasphalting processes in pilot plants, but also will help to find new geochemical biomarkers occluded within asphaltenes.

With heavy crude oil refining on the rise, upgrading strategies are fundamental to yield high-value products. Hydroconversion and thermal cracking are well-established and widely used upgrading processes for heavy oils' distillation cuts and residues. Recognizing molecular changes in these fractions after upgrading, particularly of asphaltenic compounds, is fundamental to understand and optimize the processes. In this work, we follow compositional changes in the asphaltene fraction of a Colombian heavy crude, after hydroconversion and thermal cracking, using high-resolution mass spectrometry. The liquid products from the upgrading processes were fractionated into maltenes and residual asphaltenes, with yields between 33% and 38% in maltenes from the original asphaltene feedstock. Contoured plots of double bond equivalents versus carbon number and van Krevelen diagrams show maltenic fractions exhibiting lower aromaticity, smaller molecular size, fewer heteroatomic species, and higher content of alkyl side chains than the starting asphaltenic material. Residual asphaltenes, on the other hand, consist of compounds with lower H/C ratios and reduced content of alkyl groups than the feedstock. In addition, structural information about the feedstock, such as archipelago or island structures, can be derived from the plots. This information is useful to establish trends between compound class reactivity and the suitability to produce valuable maltenic compounds through upgrading technologies.

Asphaltene adsorption properties on mineral surfaces are fundamental to understanding wettability changes in rocks and fluid behavior in reservoirs. In this contribution we report an analytical approach to investigate the molecular features responsible for asphaltene−silica interactions. We used high performance thin layer chromatography silica plates and an elutropic series of solvents to fractionate asphaltenes according to their particular affinity with the mobile and stationary phases. We observed three characteristic asphaltene fractions (with R f ́s of 0, 0.69, and 0.90), which were in turn desorbed and analyzed by atmospheric pressure photoionization FT-ICR mass spectrometry (APPI-FT-ICR-MS). In general, polar noneluted compounds highly retained by the silica surface with R f = 0 exhibit molecular compositions with N 1 , N n O o and O o (o = 1, 2, 3 and n = 1, 2) classes and the lowest H/C ratios compared to the other subfractions. Polar CH 2 Cl 2 :MeOH-eluted compounds, with R f = 0.69, have predominantly HC, N

Petroprophyrins are biomarkers used to extract information about petroleum genesis among other characteristics. Identification of particular types, such as Ni, Cu, Mn, vanadyl (VO), and oxygenated or sulfur-containing porphyrins, typically involves exhaustive isolation and purification processes followed by high-resolution mass spectrometry analysis using atmospheric pressure photoionization [APPI-(+)] or electrospray [ESI-(+)] sources. Simultaneous identification of all porphyrins present in a particular crude oil or organic-matter-rich sediment still remains an analytical challenge. Here, we report a straightforward petroporphyrin isolation and identification methodology based on a single-step liquid–liquid (L–L) extraction (crude oil: acetonitrile) and high-performance thin-layer chromatography fractionation (HPTLC, aminopropyl-bonded silica) followed by selective ionization via electron transfer in matrix-assisted laser desorption ionization (MALDI-FTICR). Mass spectrometric analysis of the extracts resulted in detection of 350 individual compounds in the acetonitrile extract and 518 in the HPTLC extract, corresponding to the porphyrin families N4VO, N4VO2, N4VO3, N4VOS, and N4Ni as verified by isotopic structure analysis. To the best of our knowledge, this observation constitutes the largest simultaneous identification of Ni, VO, and oxygenated and sulfur-containing porphyrins in a single crude oil sample. In addition, the use of MALDI significantly reduces the amount of sample required for analysis (pico to femtomole levels) in comparison with continuous infusion methods such as APPI and ESI.

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