A Comprehensive Kinetic Study of Bida Oil Shale Kerogen Pyrolysis through Isoconversional and Distributed Activation Energy Modeling

Abstract

Oil shale kerogen pyrolysis is typically crucial for optimizing production efficiency. This research investigates the thermal degradation behavior of Bida oil shale kerogen using thermogravimetric analysis (TGA) at varying heating rates (10, 20, 30, and 40 °C/min) . This study employs kinetic analysis methods including Kissinger (K), Flynn–wall–Ozawa (FWO), Kissinger-Akahira-Sunose, (KAS) and Distributed Activation Energy Model (DAEM) to elucidate the complex decomposition behavior. The research provides novel insights into the temperature-dependent variations in oil shale pyrolysis, revealing significant impacts of heating rates on decomposition temperatures and kinetics. Notably, increasing heating rates led to a shift in decomposition temperatures, attributed to differences in heat transfer efficiencies within the sample. Distinct stages of decomposition were observed, with devolatilization initiating around 260°C and progressing rapidly until approximately 526 °C, followed by a gradual decline in decomposition rate. Kinetic analysis using KAS, and FWO provided valuable insights into activation energies (Ea) and pre-exponential factors (A). Ea ranged from 64.945 to 86.94 kJ/mol, indicating a complex decomposition mechanism influenced by varying conversion levels. The DAEM further elucidated the kinetics of oil shale decomposition, highlighting the heterogeneity of pyrolytic processes under different heating rates.  The average Ea and frequency factor calculated using the DAEM method were 64.95 kJ mol^-1 and 1.87 × 105 min^-1. It was observed that the results obtained from the methods differed from each other due to the complex mechanism of reaction occurring during the pyrolysis process and the effect of different heating rates. The findings contribute to refining kinetic models for oil shale pyrolysis, shedding light on critical factors shaping thermal degradation behavior.