Identification of about 30 000 chemical components in shale oils by electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) coupled with 15 T fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and a comparison to conventional oil

The molecular composition of two shale oils (from U.S. Western and Russian Slanet mines) was studied using 15 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Together, these techniques allowed for the identification of ∼30 000 chemical components. The class and double-bond equivalence (DBE) distributions of the shale oils were compared to those of conventional oil. N_x classes were abundant in U.S. Western shale oil, and O_x and NO_x class compounds were in the Russian Slanet shale oil. The observed class distribution matched well with the high nitrogen content of U.S. Western shale oil and the high oxygen content of Russian Slanet shale oil. Aromatic hydrocarbon was significantly less abundant in the shale oils than in conventional oil. Following studies of the major components, structures were suggested in accordance with the DBE distribution of each class. The DBE distributions of the N₁ and aromatic hydrocarbon classes were lower in the shale oils than in conventional oil. O₂ compounds with DBE = 1 were abundant in the shale oils, whereas O₂ compounds with DBE = 3-4 predominated in conventional oil. These findings combined with the previously reported results suggest that shale oil resembles less biodegraded oil.