Structure characteristics and evolution mechanism of oil sands bitumen at Karamay, Xinjiang(China)

Abstract

The chemical structure largely influences the composition and distribution of pyrolysis products. Investigating the objective rules of structural characteristics and pyrolysis reactions of oil sands bitumen can enhance the knowledge of the pyrolysis reaction mechanism. This paper carried out the extensive experimental characterization of the chemical structure of Karamay oil sands bitumen (KBS) in Xinjiang, China. Then, the thermal evolution mechanism of the chemical structure of KBS was investigated by focusing on the thermogravimetric analysis and combining the characterization results of KBS at different pyrolysis final temperatures. The results show that the pyrolysis of KBS belonged to a parallel reaction. On one hand, aliphatic groups, as the main structure, undergo thermal cracking reactions to produce light oil. The oxygen-containing functional groups contributed to the production of CO and CO2. On the other hand, the aromatic structure, which has a high degree of condensation and high tightness, would condense into a more challenging to decompose coke during pyrolysis. Meanwhile, pyridinic was condensed into quaternary at this stage. The hydroxyl group in the oxygen-containing functional group structure was present in the coke due to its better thermal stability. Finally, the paper proposed the pyrolysis reaction path for the chemical structure of KBS.