Pyrolysis temperature effect on compositions of basic nitrogen species in Huadian shale oil using positive-ion ESI FT-ICR MS and GC-NCD

•Shale oils produced at constant temperature points were more representative.•A total of 14 different basic species of heteroatom compounds were identified.•The probable heteroatom core structures were suggested.•Pyrolysis temperature regularly affected abundance, DBE and carbon number. Positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography-nitrogen chemiluminescence detection (GC-NCD) was used to study the effect of pyrolysis temperature (400℃, 430℃, 460℃, 490℃, and 520℃) on basic nitrogen compounds in Huadian shale oil. Because of the effect of secondary cracking, the relative contents of aliphatic amines and anilines decreased with increase in pyrolysis temperature. The relative abundances of N1 classes decreased first but later increased. The relative abundances of N2OX and N3OX increased first but later decreased, and reached the maximum at 460 °C, which were 21.47 % and 5.27 %, respectively. As the pyrolysis temperature increased, the relative abundance of the N1 classes within the carbon number ranged from 10 to 30 obviously increased. In conclusion, the pyrolysis temperature had an effect on the number, relative abundance, DBE distribution and carbon number distribution of heteroatom compounds in shale oil.