Molecular Characterization of Aged Bitumen with Selective and Nonselective Ionization Methods by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. 1. Multiple Pressure Aging Vessel Aging Series

Abstract

Bitumen is a very complex mixture corresponding to the residue from the vacuum distillation of crude oil. The complexity of such a mixture can be defined by its composition, with several thousand molecules that may contain heteroelements such as sulfur, nitrogen, and oxygen. Almost all bitumen production is used as a binder to produce asphalt pavements. Additional additives or physicochemical treatments can be used to improve the properties and lifetime of this binder. Asphalt pavements are subject to oxidative aging over the years, which leads to deterioration of the physical properties and reduces the performance and durability of the product. To have a better understanding of such mechanisms, artificial techniques can be used to simulate oxidative aging of bitumen. The most-used technique is the pressure aging vessel (PAV) which simulates the long-term aging of bitumens. To characterize oxidative aging at the molecular level, instruments such as Fourier transform ion cyclotron resonance (FTICR) are required. The ultrahigh resolution of this analyzer allows the unambiguous attribution of molecular formulas to each signal. Electrospray ionization (ESI) source was used to selectively ionize acid molecules, while atmospheric pressure photoionization (APPI) source was used to have a nonselective ionization of low-polarity molecules from bitumen. Analyses were carried out on four different PAV aging times (PAV-0h, 25h, 72h, and 96h) to characterize the aging kinetics from a bitumen sample. ESI results allowed the revealing of significant differences from the heteroatom class and family distributions starting from PAV-72h. It was defined by a general decrease of nonoxygenated families (N x and N x S y ) and by an increase of oxygenated families (O z , N x O z , O z S y , and N x O z S y ). The van Krevelen plot evidenced that aging markers correspond to low double bond equivalent (DBE) molecules. The occurrence of aldehydes and fatty acids (DBE 1) with aging in the CHO z family was characterized with DBE versus carbon number plots. Aging markers from O z S y were also characterized with occurrence of benzothiophenic (O 2 S 1 ) and sulfonic acids (O 3 S 1 ). Logically, less meaningful results were obtained with APPI. However, this nonselective source allowed the ionization of thiophenes, furans, cycloalkanes, and polycyclic aromatic hydrocarbons that were not observed in ESI measurements. Homogenic decreases in the distribution of nonoxygenated compound classes (HC, S 1 , S 2 , and N 1 ) were observed. Concerning the oxygenated molecules, an expansion of the distribution was observed, but without the occurrence of specific aging markers. Oxidation seemed to be favored on linear and naphthenic molecules and not on the highly aromatic ones.

Molecular Characterization of Aged Bitumen with Selective and Nonselective Ionization Methods by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. 3. Investigation on Molecular Fractions Obtained by Gel Permeation Chromatography

“…For the O 1 compound class, major signals were majorly found at very low DBE values (1–2). These molecules could correspond to aldehydes with long alkyl chains as it was previously proposed . Although two distributions were observed for the N 1 O 1 compound class, signals were found for aromatic molecules with the major ones starting at DBE 10, which was consistent with carbazole structure with a ketone function.…”

“…As it was expected and highlighted in the study of whole bitumen sample analysis, only few differences were observed on the compound distributions with aging using APPI. 29,30 A slight increase of low DBE molecules can be evidenced on the LMW fraction for HC, S 1 , and O 1 S 1 compound classes. Concerning the MMW fraction, only expansions of O 1 and O 1 S 1 distributions can be distinguished, which underlined once again that it was not in this fraction that the oxidation markers can be evidenced.…”

Molecular Characterization of Formulated Lubricants and Additive Packages Using Kendrick Mass Defect Determined by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…32,33 Given the high diversity of heteroatom and metals present in such samples, molecular formula assignments cannot be carried out directly as is classically done for petroleum sample. 34 Indeed, with all possible elements, too many molecular formula would have been possible even with our subppm mass accuracy. For instance, with reasonable elemental composition constraints set with N 6 O 6 S 6 P 2 Zn 1 for the ion at m/z 728.28, and an error tolerance set at 0.5 ppm, more than 30 possible molecular formulas were proposed by DataAnalysis software.…”

“…Given the high diversity of heteroatom and metals present in such samples, molecular formula assignments cannot be carried out directly as is classically done for petroleum sample . Indeed, with all possible elements, too many molecular formula would have been possible even with our subppm mass accuracy.…”

Characterization of Crude Oil Molecules Adsorbed onto Carbonate Rock Surface Using LDI FT-ICR MS

“…Therefore, a detailed molecular description of the species adsorbed to the rock surface should shed light on which factors of a crude oil-brine-rock system are important in improved oil recovery. Fourier transform ion cyclotron resonance mass spectrometry has been extensively used in petroleomics. − The outstanding resolving power and mass accuracy provided by Fourier-transform ion cyclotron resonance (FT-ICR) instruments enable the characterization of the incredibly complex mixtures found in the oil industry. However, reports of the ultrahigh-resolution mass spectrometry molecular characterization of crude oil species adsorbed onto rock surfaces are not abundant in the literature.…”