Gasolines and other hydrocarbon fuels are known to form macromolecular deposits, broadly termed “gums” during storage and high temperature stress. The formation of gums is associated with numerous adverse effects such as filter clogging, engine stalling, and knocking. Although gum formation is a complex multi-step process, olefins have been inextricably identified as major contributors. While numerous methods exist to determine the total olefin content in hydrocarbon fuels, methods to comprehensively profile olefins are lacking. Herein, we demonstrate an advanced method for profiling olefins in fuels, including species-level identifications as well as the distribution of olefins by carbon number. To accomplish this, we use an advanced analytical workflow involving the treatment of gasoline with elemental bromine (Br<sub>2</sub>) to selectively react olefins, followed by analysis by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) is reported. First, gasoline is treated with Br<sub>2</sub>, which selectively reacts with olefins to produce dibromoalkanes. Based on the known reaction chemistry, the dibromoalkane species identified in the gasoline can be mapped back to the corresponding olefin in the original sample. For initial method development, a sample of standards containing alkanes, alkenes, and aromatic species was brominated and high selectivity towards alkenes was demonstrated. To show applicability to a real-world sample, a locally source gasoline sample was brominated and subsequently analyzed. Using a combination of brominated olefin standards and the ordered structures of the GC×GC chromatograms, numerous olefin species could be definitively identified in the gasoline sample.

Profiling olefins in gasoline by bromination followed by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

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