A comprehensive kinetics study on non-isothermal pyrolysis of kerogen from Green River oil shale

Fundamentally understanding the pyrolysis kinetics of kerogen is of prime scientific and industrial importance. Herein, bitumen- and carbonates-free kerogen sample is prepared through Soxhlet extraction followed by decarbonation of Green River oil shale, and its pyrolysis is studied by non-isothermal thermogravimetric analysis. The systematic analyses show that both the Popescu and master plots methods are not applicable to describe the kerogen pyrolysis process due to the changed reaction model and the varied activation energy over certain conversion range, respectively, while the piecewise non-linear least squares analysis is identified as an effective method to discriminate the most probable kinetic model from commonly used 15 reaction models based on four solid-state pyrolysis mechanisms. Two-stage reaction model, i.e., F1 at the early stage and F2 at the later one, is proposed to well describe the kerogen pyrolysis process, which demonstrates a wide applicability owing to their insensitivities on the heating rate and estimation methods of the activation energies. The methodology revealed here could be applicable to determine other solid-state pyrolysis kinetics and reaction mechanism.