Characteristics of Thermal Bitumen Structure as the Pyrolysis Intermediate of Longkou Oil Shale

Abstract

The effects of pyrolysis temperature on the structure of thermal bitumen as the pyrolysis intermediate of Longkou oil shale are investigated through electron paramagnetic resonance spectroscopy, Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, gas chromatography–mass spectrometry (GC-MS), and X-ray photoelectron spectroscopy (XPS). Results indicate that the free radical concentration of thermal bitumen increases at a maximum temperature of 410 °C and then decreases between 410 and 450 °C. Moreover, the g factors of thermal bitumen are slightly higher than 2 and decrease with increasing temperature because of the aromatization of saturates and decarboxylation. FTIR analysis indicates that decarboxylation is completed before the temperature reaches 370 °C. NMR analysis shows that aliphatic and aromatic compounds comprise more than 80% and 15–16% thermal bitumen, respectively. During pyrolysis, the fraction of aliphatic compounds, branched alkane, and the average...