Isoconversional Methods for Kinetic Modeling of Kerogen Pyrolysis Using TG Data

The pyrolysis kinetics of the Jordanian Lajjun oil shale kerogen was investigated inside a TGA reactor. Kerogen samples (extracted by mineral digestion) were non-isothermally heated at rates varying from 1 to 50°C/min under 350-550C in N2 atmosphere. Friedman, Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) models were employed to estimate the kinetic parameters at isoconversional points ranging from 0.1 to 0.9. The value of the calculated apparent activation energy (E) was found to vary with both the employed model and the conversion (x). Using the three models, the calculated increased with from 10 to 30% (low level), and then decreased with from 30 to 60% (medium level). At high level (60 to 90%), however, increased with increase using both KAS and FWO models, while it continuously dropped with increase using Friedman model. The frequency factor (k0) calculated form each model was found to linearly correlate with E. Compared to KAS and FWO models, Friedman' provided a more accurate fit to the experimental data.