Desulfurized Fuels from Athabasca Bitumen and Their Polycyclic Aromatic Sulfur Heterocycles. Analysis Based on Capillary Electrophoresis Coupled with TOF MS

Abstract

Polycyclic Aromatic Sulfur Heterocycles (PASHs) are undesirable compounds in fuels and refined petroleumbased products. Capillary electrophoresis (CE) was investigated as an alternative to analyze the preisolated PASHs from partially desulfurized materials derived from Athabasca, Canada, bitumen. The sample complexity is considerably reduced by this preisolation by ligand exchange chromatography on a Pd(II) containing phase and subsequent ionization of the neutral PASHs through S-methylation to impart electrophoretic mobility. The PASH components are separated and characterized using CE with a time-of-flight mass spectrometer (TOF MS) as detector. An additional major advantage of the CE separation is that the drawbacks of HPLC (limited separation efficiency) and GC (volatility limitations) for separations of high molecular weight compounds can be circumvented. CE was demonstrated to be a highly efficient method in the separation of PASHs and up to 200,000 theoretical plates were obtained. The practicability of the method was shown by an extensive qualitative analysis of the PASH fraction of a hydrotreated middle distillate and a hydrotreated heavy gas oil. Additional information on the sample composition like the identity of parent ring systems, the alkyl substitution, and hydrogenated products from the hydrodesulfurization was gained through the use of CE-TOF MS and measuring standard PASHs expected to be present. The results are compared with GC-MS and high-resolution Orbitrap measurements of the same samples.

Retention behavior of isomeric polycyclic aromatic sulfur heterocycles in reversed-phase liquid chromatography

“…In recent decades, PAHs are one of the most studied groups of environmental contaminants because of their high carcinogenic and mutagenic potential [1–4]. However, their sulfur analogues, polycyclic aromatic sulfur heterocycles (PASHs), have received far less attention although their presence has been confirmed in air particulate matter [5, 6], sediments [7–9], coal liquids [10], diesel [9], heavy oil [11], crude oil [9, 11–17], shale oil [10, 12, 15, 18], coal tar [12–15, 19–21], mussels [7, 8], and fish [7, 8]. In addition, their carcinogenic and mutagenic potential have been reported [22, 23].…”

Retention behavior of alkyl-substituted polycyclic aromatic sulfur heterocycles in reversed-phase liquid chromatography

“…1) on both monomeric and polymeric C 18 stationary phases. In past decades, PASHs have received far less attention than PAHs despite their carcinogenic and mutagenic potential [9, 10] and their presence in air particulate matter [11, 12], sediments [13–15], coal liquids [16], diesel [15], heavy oil [17–21], crude oil [15, 18, 22–31], shale oil [16, 22, 32, 33], coal tar [22, 23, 29, 34–36], mussels [13, 14,], and fish [13, 14,]. In a previous study [37], we reported LC retention indices for 70 PASHs on both monomeric and polymeric C 18 phases.…”

Atmospheric pressure chemical ionization Fourier transform ion cyclotron resonance mass spectrometry for complex thiophenic mixture analysis

“…Currently, PASHs are derivatized to S ‐methyl sulfonium or S ‐phenyl sulfonium salts as an approach to the selective ionization of PASHs in a complex hydrocarbon mixture . This enables direct detection of PASHs by ESI coupled with ultrahigh‐resolution mass spectrometers such as a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer or an LTQ Velos Orbitrap mass spectrometer . Recently, atmospheric pressure photoionization (APPI) was used for the analysis of sulfur compounds in petroleum fractions .…”

“…[21] This enables direct detection of PASHs by ESI coupled with ultrahighresolution mass spectrometers such as a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer or an LTQ Velos Orbitrap mass spectrometer. [22,23] Recently, atmospheric pressure photoionization (APPI) was used for the analysis of sulfur compounds in petroleum fractions. [24] However, the simultaneous production of protonated [M + H] + , deprotonated [M-H] + and molecular ions [M +• ] in the source complicates the interpretation of data obtained from real-world samples which often contain several thousand analytes.…”