Thermal oxidation study of Moroccan oil shale: A new approach to non-isothermal kinetics based on deconvolution procedure

Abstract

In this paper, we have employed multi-stage parallel reaction approach and Fraser–Suzuki distribution method to fit the non-isothermal TG/DTG curves resulting from oxidation of Moroccan Timahdit (X-layer) oil shale. The kinetic study was conducted to overcome the insufficiencies of the previous works, which oversimplified the oxidation processing having complex behaviors. The differential curves (DTG) of thermal oxidation of Timahdit organic matter were separated into two independent reactions. Based on the results of the deconvolution method, the kinetic mechanism was obtained using Malek’s procedure, followed by the determination of the apparent activation energy Eα using isoconversional model free methods of Friedman, Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS). The obtained values of Eα show that the first oxidation process is more energetic than the second. This behavior is correlated to nature of organic matter including in Timahdit oil shale. The kinetic modeling results for each individual peak showed that the thermal oxidation process is controlled by nth order reaction mechanism with n>1, unlike to simple first order mechanism predicted by fitting methods.