Thermal analysis studies of oil shale residual carbon

Thermal analysis has been used to determine the impact of heating on the decomposition reaction of two Moroccan oil shales between ambient temperature and 500degreesC. During pyrolysis of raw oil shale, the residual organic matter (residual carbon) obtained for both shales depends on the heating rate (5 to 40degreesC min(-1)). Three stages characterize the overall process: the concentration of carbonaceous residue decreases with increase of heating rate, become stable around 12degreesC min(-1) and continue to decrease at higher heating rates. Activation energies were determined using the Coats-Redfern method. Results show a change in the reaction mechanism at around 350degreesC. Below this temperature, the activation energy was 41.3 kJ mol(-1) for the decomposition of Timahdit, and 40.5 kJ mol(-1) for Tarfaya shale. Above this temperature the respective values are 64.3 and 61.3 kJ mol(-1). The reactivity of Timahdit and Tarfaya oil shale residual carbon prepared at 12degreesC min(-1) was subject to a dynamic air atmosphere to determine their thermal behaviour. Residual carbon obtained from Tarfaya oil shale is shown to be more reactive than that obtained from Timahdit oil shale.