Characterization of nitrogen and sulfur compounds in hydrocracking feedstocks by Fourier transform ion cyclotron mass spectrometry

Advanced characterization of two heavy hydrocracking unit feedstocks, Heavy Vacuum Gas Oil (HVGO) and De-Metallized Oil (DMO), both derived from Arabian Light crude oil, was performed using High Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) to gain in-depth information on their aromaticity characteristics and heteroatom content, i.e., sulfur- and nitrogen-compounds. In order to obtain chemically utilizable information, each individual mass signal in the high resolution mass spectra was linked to its underlying elemental composition, the relevant double bond equivalent (aromatic properties), and carbon number. The DMO differs from the VGO in the N-, and S-species distribution patterns. The DMO contains heavier and more condensed aromatic species than the HVGO. Species with up to three sulfur- and up to two nitrogen-atoms per molecule were found in both feedstocks. Nitrogen is present in both feedstocks in pyrrole- and pyridine-structures. Besides, numerous mono-, di-, and trisulfur species and acridines and carbazoles that contain I to 3 additional sulfur atoms in the same molecule were found in both feedstocks.