High-Field Orbitrap Mass Spectrometry and Tandem Mass Spectrometry for Molecular Characterization of Asphaltenes

Abstract

This work introduces a novel approach by use of high-energy collision-induced dissociation for fragmenting asphaltenes into their constituent stable aromatic cores as a means for determining the relative proportions of island-to-archipelago structures. This approach is particularly useful for comparing asphaltenes from various crude oils. Ion generation from asphaltenes was performed by use of atmospheric pressure photoionization, which has been demonstrated to provide hydrogen-to-carbon ratios consistent with bulk measurements by combustion analysis with less than 10% relative error. The fragmentation behavior of asphaltenes was first evaluated with model compounds consisting of island and archipelago structures by use of low- and high-energy collision-induced dissociation (CID and HCD). Unlike CID, HCD enables dissociation of model compounds to their stable aromatic cores. This allows facile classification as either island or archipelago on the basis of the discrepancy in the double-bond equivalents between the precursors and stable aromatic cores. Model compound studies also showed that when HCD is utilized for the simultaneous dissociation of multiple precursor ions, efficient fragmentation of all precursors only occurs when ions within a narrow mass window are presented for analysis. The HCD approach was then applied to characterize narrow mass segments of crude oil asphaltenes, including those derived from hydrotreated resids. Observed island-to-archipelago proportions were consistent with the chemical transformations that occur during the hydrotreating process. Importantly, the method also demonstrates that the proportion of island-to-archipelago structures in asphaltenes decreases with increase molecular weight.

High resolution nanoscale chemical analysis of bitumen surface microstructures

“…The outer edge of the peri-phase shows a slightly lower number of aromatic compounds than the inner part of the peri phase. The lateral distribution of molecular compounds with a mass greater than 950 u, are typical indicators of asphaltenes with fused rings 48 as well as high mass tail of aromatic compounds 49 – 53 , were found in higher concentration in the para phase and were less in the outer part of the peri phase and the catana phase. Resins corresponding to ions such as C 6 H 9 O 5 + and C 7 H 11 O 5 + were found on the outer edge of the peri phase.…”

Fractionation and Characterization of Petroleum Asphaltene: Focus on Metalopetroleomics

“…Thus, APPI is widely used to characterize the molecular composition of petroleum asphaltenes and other components [39,40]. Although the resolution of Orbitrap is not as high as that of FT-ICR, its resolution ability cannot be ignored, and its stronger isolation and collision capabilities have unique advantages in studying the molecular composition and structural information of asphaltenes [41]. In addition, other ionization techniques (e.g., APCI, APLI, LDI, MALDI, and ASAP) equipped with ultra-high-resolution mass spectrometers are also applied to characterize asphaltenes [42][43][44][45][46].…”

Comprehensive analysis of multiple asphaltene fractions combining statistical analyses and novel visualization tools

“…Asphaltenes often containin heteroatoms such as N, O, or S [21,22], which may exacerbate handling issues, cause catalyst fouling, or alter responsiveness to additives [10,23]. Island and archipelago-type asphaltenes, defined as a single PAH cores substituted with alkyl chains or multiple PAHs bridged by alkyl linkers, respectively, have both been detected [24][25][26]. Interpretation of asphaltene core structure, and comment on the likely predominance of island or archipelago-type asphaltenes using Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) analyses has previously included inspection of fragment ion spectra, comparison of average molecular weight (Mw), plots of double bond equivalent (DBE) against carbon number, and DBE distributions [25][26][27][28][29].…”

“…Although a precise definition of the compositional boundaries for island and archipelago-type asphaltenes has not yet been attained, it is possible to keep experimental procedures constant between analyses and use consistent compositional boundaries for comparisons of samples. Such an approach allows for differences in ionization efficiency between the two structures [24]. Following fragmentation both neutral and ionic fragments will be generated, with highly condensed asphaltene cores or smaller aromatic moieties detected depending on which carries the charge from the precursor.…”