Selective molecular characterization of olefins in hydrocarbon mixtures by Ag+ complexation ESI high-resolution mass spectrometry

Abstract

Molecular characterization of olefins in the complex hydrocarbon mixture is of vital importance for the various hydrocarbon upgrading processes. According to the strong interaction of Ag+ with unsaturated hydrocarbon, Ag+ complexation was adopted in this study as a tool to achieve selective olefin ionization in electrospray ionization (ESI). High-resolution mass spectrometry (HR MS) was used to characterize ionized olefin molecular composition. Various model compounds, including paraffins, naphthenes, olefins, and aromatics, were used to verify the ionization selectivity. The observed olefin carbon number distribution from Ag+ complexation ESI HR MS was in agreement with those from gas chromatography-mass spectrometry equipped with the electron impact ion source (GC-EI-MS). The proposed method can be conveniently used for direct molecular characterization of olefins in mixtures without time-consuming olefin pre-separation or chemical derivatization. Olefins in coker diesel, coal tar liquid, and Fischer-Tropsch wax were successfully analyzed by the proposed method.