THE CHEMICAL COMPOSITION AND PYROLYSIS CHARACTERISTICS OF THERMAL BITUMEN DERIVED FROM PYROLYZING HUADIAN OIL SHALE, CHINA

摘要

Thermal bitumen is an important intermediate derived from kerogen decomposition during oil shale pyrolysis. In this study, thermal bitumen was obtained by extracting oil shale char generated from pyrolysis of Huadian oil shale at 360-530 degrees C. The chemical composition and pyrolysis characteristics of bitumen were investigated by ultimate analysis, liquid chromatography fractionation, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The decomposition of oxygen-containing structures at 420-450 degrees C decreased the oxygen content from 4.66 to 0.75 wt%. The intense cracking of aliphatic compounds or alkyl chains at 450-480 degrees C resulted in the selective concentration of aromatic compounds and the decrease of H/C ratio from 1.350 to 1.262. The pyrolysis of thermal bitumen could be tentatively divided into two stages - the evaporation of light components (150-410 degrees C) and the cracking of heavy components (410-550 degrees C), which corresponded respectively to a shoulder and an obvious peak in differential thermal gravimetry (DTG) curves. For pyrolysis of oil shale, the evaporation process dominated the pyrolysis of thermal bitumen at 420-450 degrees C, which decreased the content of light components. In a higher temperature range, 450-480 degrees C, the cracking of large molecules became more intense and, as a result, increased the content of light components and decreased that of heavy components.