Exploring Occluded Compounds and Their Interactions with Asphaltene Networks Using High-Resolution Mass Spectrometry

Abstract

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.

Investigation of Island/Single-Core- and Archipelago/Multicore-Enriched Asphaltenes and Their Solubility Fractions by Thermal Analysis Coupled with High-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…Due to extensive washing [50,52], the whole asphaltene samples do not reveal appreciable amounts of occluded compounds during thermal analysis [33,44]. Nonetheless, after the extrography fractionation, occluded compounds can be successfully exposed and seem to be enriched in several fractions, especially in the acetone fraction.…”

“…This bimodal distribution was also prior observed for mid-polar fractions of occluded CH-, O1-, and S1-class compounds of a Colombian asphaltene. [52] Highly aromatic compounds with short alkylation were classified as "asphaltene-like" structures, while low-DBE compounds were classified as "maltene-like" structures, forming a compositional gap between both regions. [52] Furthermore, the results indicate that aggregation has large influences on the release 435 of the occluded material during the heating process.…”

“…[52] Highly aromatic compounds with short alkylation were classified as "asphaltene-like" structures, while low-DBE compounds were classified as "maltene-like" structures, forming a compositional gap between both regions. [52] Furthermore, the results indicate that aggregation has large influences on the release 435 of the occluded material during the heating process. In the whole asphaltene samples, the occluded compounds may be prevented from TG desorption by cooperative aggregation, which can explain the absence of species in the desorption phase.…”

Asphaltenes: Separations, structural analysis and applications

“…Generally, MWs of asphaltenes vary from 5 × 10 2 to 2 × 10 3 with average value around 700 Da [20] , but it may occasionally extend up to 10,0 0 0 [45][46][47] . While, MW is considered to be 4 × 10 3 -10 4 for a cluster or particle weight and possibly 4 × 10 4 -4 × 10 7 for a micelle [9,23] .…”

Modelling approach for multi-criteria decision-making selection process for artificial lift systems in crude oil production

“…Several works have shown that asphaltene aggregates display greater interfacial activity within the W/O interface than the solvated (free) asphaltenes that, in fact, are not structurally able to be absorbed over this surface [2,37]. This implies that the key to understanding this behavior is in the nature of the compounds that interact with asphaltenes and can co precipitate with them (occluded compounds).…”