Direct Insertion Analysis of Polymer-Modified Bitumen by Atmospheric Pressure Chemical Ionization Ultrahigh-Resolution Mass Spectrometry

Abstract

Bitumen is a highly complex matrix, generally obtained as vacuum residues of the crude oil distillation. This material is majorly used as binder for the construction of asphalt pavement. Mechanical properties of bitumen are greatly influenced by its composition, including heteroatom-containing compounds, and by the use of additive cocktails. Polymer-modified bitumen (PMB) can be produced by the use of additives such as styrene–butadiene–styrene copolymer (SBS) to avoid asphalt stiffness and pavement cracking. To characterize a complex mixture such as bitumen at the molecular level, instruments such as Fourier transform ion cyclotron resonance are required. However, the size of SBS, which is typically >150 kDa, is far above the mass range of Fourier transform ion cyclotron resonance (FTICR) instruments. Direct insertion probe atmospheric pressure chemical ionization (DIP-APCI) can be used to pyrolyze SBS and observe its fragments within a PMB sample in a lower mass range. This technique does not require any sample preparation because the sample is analyzed in pure form and is also adapted to characterize heavy petroleum products with its ability to ionize a large range of molecules including nonpolar, polar, and aromatic species. DIP-APCI-FTICR was used with fixed and ramped temperature for the analysis of base bitumen, SBS, and PMB samples. It allowed for the characterization of the thermodesorption products of bitumen and the pyrolysis products of SBS. The main markers of SBS appear to be multimeric butadiene ions. This SBS ion series is clearly evidenced in PMB using DBE vs C# and modified Kendrick mass defect plots. Overall, this study presented a fast DIP-APCI-FTICR characterization of bitumen and PMB without any sample preparation.

Review on Evolved Gas Analysis Mass Spectrometry with Soft Photoionization for the Chemical Description of Petroleum, Petroleum-Derived Materials, and Alternative Feedstocks

“…With the broad introduction of atmospheric pressure ionization (API) in mass spectrometry in the late 1990s and early 2000s, EGA–MS concepts operating at atmospheric pressure have also been brought to market. Here, a substantial number of solutions were presented over the last 2 decades, including thermogravimetric coupling with API , or multiple versions of atmospheric pressure direct insertion probes. , Moreover, modern concepts have developed from simplistic manual experiments to fully automated measurement and data analysis solutions, some featuring autosampler capabilities. , In the following, the general concepts of the prevalent EGA solutions for mass spectrometric coupling with soft photoionization are briefly presented. Figure a schematically summarizes the technical concepts and types of construction, whereas Figure b presents the general thermochemical conversion pathways of matrices in energy and fuels research.…”

“…The characteristic polymer degradation pattern, for example for the styrene–butadiene–styrene copolymer, could be observed next to the ultracomplex evaporation profile of the bitumen chemical space. Interestingly, the Kendrick mass defect and carbon number versus DBE visualization allowed for the efficient mapping of the additive . Moreover, also chemical changes in the complex bitumen matrix during short-term aging were investigated, combining GC × GC–MS and TG–APCI–MS.…”

“…Here, a substantial number of solutions were presented over the last 2 decades, including thermogravimetric coupling with API 72,73 or multiple versions of atmospheric pressure direct insertion probes. 74,75 Moreover, modern concepts have developed from simplistic manual experiments to fully automated measurement and data analysis solutions, some featuring autosampler capabilities. 71,76 In the following, the general concepts of the prevalent EGA solutions for mass spectrometric coupling with soft photoionization are briefly presented.…”

“…105 Without the mass loss information and limited in upper temperature but with higher throughput and easier handling, DIP APCI and APPI MS were used in multiple studies for fossil petroleum analysis. 74,131 Afonso and co-workers extensively studied the characteristics of DIP (and the analogous Waters Corporation ASAP) for the analysis of vacuum gas oils, 131 polyalphaolefins, 132 lubricants, 133 but also polymers. 134,135 A comparison of the results received by DIP and direct infusion approaches, such as ESI, APCI, and APPI, on vacuum gas oils revealed the suitability of the DIP approach for speciation of aromatic sulfur-containing compounds.…”

“…Interestingly, the Kendrick mass defect and carbon number versus DBE visualization allowed for the efficient mapping of the additive. 74 Moreover, also chemical changes in the complex bitumen matrix during short-term aging were investigated, combining GC × GC−MS and TG−APCI−MS. Oxidation processes were revealed to be prevalent for the CH and CHS class compounds.…”