Compositional Study of Polar Species in Untreated and Hydrotreated Gas Oil Samples by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI FTICR−MS)

Abstract

Two gas oil samples, untreated feed and hydrotreated product oil, were analyzed. Both basic and acidic polar species were detected by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry, and the detected species were characterized on the basis of their elemental compositions. Samples were real refinery samples, with one sample being a certain distillation fraction of crude oil (feed) and the other sample being a hydrotreated feed oil (product). Comparison of the compositions of untreated and hydrotreated oil provides insight into (1) compounds that are resistant to processing, (2) compounds that are removed/degraded by processing, and (3) new compounds that are produced during processing. N1 class compounds were found to be the most abundant basic species in both oil samples. In addition, the proportion of N1 class compounds was clearly greater in the product oil than in the feed oil, which indicates that these basic species must be resistant to removal by hydrotreatment. All basic NxOy-, NxSz-, and NxOySz-containing compounds that were detected in the feed oil were completely removed by hydrotreatment. However, some of the OySz compounds remained in the oil after hydrotreatment. Negative-ion ESI revealed that the majority of the acidic polar species in the product sample were N1 compounds, which was also the predominant class in the feed sample. The second most abundant species were the Oy-containing compounds. All of the O1 compounds that were detected in the feed oil were degraded during the hydrotreatment process, as were the O2 compounds with double-bond equivalent (DBE) values >4. Acidic NxOy-, NxSz-, OySz-, and NxOySz-containing compounds were not completely removed by the processing, but the relative abundances of these species were no longer significant in the product oil.