Influence of heating rate on basic nitrogen-containing species content in Dachengzi shale oil studied by positive-ion electrospray ionization FT-ICR mass spectrometry

Shale oil samples were produced by pyrolysis of Dachengzi oil shale, China, in a fixed bed reactor at a heating rate ranged from 5 to 20 degrees C min(-1) under argon atmosphere, at the same final temperature of 520 degrees C and residence time of 20 minutes. Positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was employed to study the influence of heating rate on the basic nitrogen species content in the shale oil. The results show that increasing the heating rate results in the increase of total and basic nitrogen contents and the number of basic nitrogen species. Among all basic classes identified from positive-ion ESI FT-ICR mass spectra, the relative abundance of N-1 class decreases while that of N1O1, N1O2, N1O3 and N-2 classes increases as heating rate increases. With increasing heating rate the relative abundance of pyridines, whose DBE is 4, decreases significantly and that of N-1 class species with DBE = 5-11 slightly, while species with DBE over 11 increase slightly. Furthermore, for pyridines and quinolines (DBE = 7) a relative obvious decrease in relative abundance is mainly observed in those species whose carbon numbers remain between 21 and 37 as heating rate increases. The relative abundance of N1O1 and N1O2 class species, whose DBE is in the range of 10-21, increases.