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SINCE 1984
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Oil Shale
ISSN 1736-7492 (Electronic)
ISSN 0208-189X (Print)
Impact Factor (2021): 1.442
PDF | doi: 10.3176/oil.2008.4.04

A. Aboulkas, K. EL HARFI

In this research, thermal characteristics and kinetic parameters of Tarfaya oil shale and its kerogen samples were determined by thermogravimetry (TG/DTG) under non-isothermal heating conditions. The pyrolysis experi­ments were performed increasing the temperature up to 1273 K at heating rates of 2, 10, 20 and 50 K/min in an inert atmosphere of nitrogen. The mass loss curve showed that pyrolysis of kerogen took place mainly in the range of 433–873 K. At higher temperatures there was a significant mass loss due to decomposition of mineral matter. It has been found that for oil shale and its kerogen analysed using the TG/DTG, the increase in the heating rate shifts the maximum rate loss to a higher temperature. Kissinger-Akahira-Sunose, Friedman, Flynn-Wall-Ozawa and Coats–Redfern methods were used to determine the apparent activation energies of materials' degradation. The analyses of the process mechanism by the methods of Criado et al. and Coats-Redfern showed that the most probable model for the pyrolysis process of organic matter of oil shale agrees with the diffusion model (D4 mechanism), and the thermal degradation process of isolated kerogen cor­responds to a mechanism involving a simple n-order model (F1 mechanism). The apparent activation energies for the organic matter of oil shale and isolated kerogen were 80–87 and 69–76 kJ/mol, respectively. A single kinetic expression is valid over the temperature range of kerogen pyrolysis between 433 and 873 K. In addition, the results indicate that the removal of mineral matter affected the kinetics and mechanism established for kerogen in oil shale.


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