Study on evolution mechanism of the pyrolysis of chang 7 oil shale from Ordos basin in China

In-situ pyrolysis of oil shale is a sophisticated process that converts solid to gas and liquid. There is currently minimal research on the chemical mechanism of the production process. Using the Chang 7 oil shale in the Ordos basin in China as an example, thermogravimetry, scanning electron microscopy, and oil shale pyrolysis are used to examine the pyrolysis process, mineral composition, and pore structure characteristics of oil shale. The results indicate that organic matter is entirely pyrolyzed as temperature rises. The organic matter is first pyrolyzed into asphaltene at low temperatures (320-450 degrees C), and the C-H bond of hydrocarbon molecules break and recombine to generate lipid compounds. In the medium temperature pyrolysis (450-600 degrees C), a substantial amount of organic matter is pyrolyzed, ester compounds undergo pyrolysis reaction, and macromolecular alkanes undergo dehydrogenation and chain breaking reaction to form small molecule hydrocarbons and hydrogen. In the high temperature pyrolysis (600-700 degrees C), secondary cracking of organic matter pyrolysis products, dehydrogenation of naphthenic hydrocarbons, polymerization of some polycyclic aromatic hydrocarbons to generate colloidal, asphaltene and oil shale semi-coke. As temperature rises, clay minerals are completely pyrolyzed, and the number of micropores and microcracks in oil shale increases as well.

Automated summary

In this study, the pyrolysis process, mineral composition, and pore structure characteristics of Chang 7 oil shale in the Ordos basin in China were investigated using thermogravimetry, scanning electron microscopy, and oil shale pyrolysis. The results showed that as the temperature increased, the organic matter underwent complete pyrolysis, with the formation of asphaltene at low temperatures (320-450 degrees C) and the generation of lipid compounds through the breaking and recombination of C-H bonds. At medium temperatures (450-600 degrees C), a significant amount of organic matter was pyrolyzed, resulting in the pyrolysis reaction of ester compounds and the dehydrogenation and chain breaking reactions of macromolecular alkanes to form small molecule hydrocarbons and hydrogen. High temperature pyrolysis (600-700 degrees C) led to secondary cracking of organic matter pyrolysis products, dehydrogenation of naphthenic hydrocarbons, and the polymerization of some polycyclic aromatic hydrocarbons to generate colloidal, asphaltene, and oil shale semi-coke. With the increase in temperature, clay minerals were completely pyrolyzed, leading to an increase in the number of micropores and microcracks in oil shale.