Experimental and mechanistic study on isothermal oxidative pyrolysis of oil shale

摘要

The reasonable introduction of oxygen to the in situ conversion process of oil shale can effectively reduce energy consumption. However, current studies on oxidative pyrolysis often proceed under non-isothermal conditions with sharp fluctuations in temperature which hinders the accurate determination of the reaction process and the corresponding temperature in the system. In this work, we study the isothermal oxidative pyrolysis behavior of two oil shales differing in total organic carbon (TOC) at constant temperatures. The results indicated that with the increase in reaction temperature, low-temperature oxidative pyrolysis (LTOP) and high-temperature oxidative pyrolysis (HTOP) can be distinguished, where the transition temperature is approximately 340 celcius. During the LTOP, kerogen undergoes low-temperature oxidation, including oxygen addition, isomerization, and decomposition reactions. As for the HTOP, high-temperature oxidation coexists with the pyrolysis of kerogen and the subsequent coke oxidation. The pyrolysis reaction gradually dominates the entire reaction with increasing temperature. Accordingly, a temperature-dependent reaction model of oxidative pyrolysis of oil shale in isothermal conditions was validated and the real-time change in the reaction rates was obtained. Also, oil shale with a higher TOC has a more intense reaction and a higher transition temperature of HTOP and LTOP. This work provides a theoretical basis for the further application of oxidative pyrolysis in oil shale exploitation.