Molecular analysis of nitrogen-containing compounds in vacuum gas oils hydrodenitrogenation by (ESI+/-)-FTICR-MS.

• VGO from conversion processes have a very different distribution of neutral nitrogen species than straight run VGOs. • Transition of neutral to basic N-species was observed for heavy coker gas oil. • DBE shift in basic nitrogen species depends on the number of the carbon atoms. • Neutral species with high DBE convert into carbazoles, which are "refractory". • Isomeric characterization is necessary for the selection of the reactivity descriptors. This paper is a part of a study on reactivity descriptors in vacuum gas oil hydrotreatment (VGO HDT). It aims to understand the differences in feeds of various process origins and the corresponding hydrotreated effluents on a molecular level. Four different vacuum gas oils were hydrotreated over a sulfided NiMo/Al 2 O 3 catalyst at a wide range of temperatures and residence times in order to collect HDT effluents at a broad range of hydrodenitrogenation (HDN) conversions. Vacuum gas oils and HDT effluents have been analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) in positive ESI(+) and negative ESI(-) electrospray ionization modes to characterize the basic and neutral nitrogen-containing species and the subtleties of HDT transformations depending on the feedstock type. [ABSTRACT FROM AUTHOR]