The kinetic modeling of the non-isothermal pyrolysis of Brazilian oil shale: Application of the Weibull probability mixture model

The detailed kinetic analysis of the non-isothermal pyrolysis of Brazilian oil shale was carried out using thermogravimetric analysis (TGA) and the derivative thermogravimetry (DTG). The investigated process was modeled using a statistical Weibull 2-component mixture model. By using different kinetic methods, it was found that the investigated process is very complex. Application of the differential and the integral isoconversional methods showed that the pyrolysis of Brazilian oil shale takes place through three reaction steps. It was found, that the third reaction step of the investigated pyrolysis process cannot be modeled by the simple first order reaction kinetics. It was established that the third reaction step can be described with the n-th order (n≠1) kinetics, including f(α)=(1−α)1.23 mechanism function. The kinetic compensation effect (KCE) was identified for observed oil shale pyrolysis. Based on the behavior of the shape parameter (θ) in complex statistical model under the consideration, it was determined that no change in the rate-limiting step occurs for the investigated pyrolysis process.