The kinetics of the thermal decomposition of green river oil shale kerogen by non-isothermal thermogravimetry

Abstract

The kinetics of the thermal decomposition of Green River oil shale kerogen have been studied by non-isothermal thermogravimetry. Kerogen decomposes to a bitumen intermediate with an activation energy of 62.10 kJ mole −1 and a frequency factor given by ≈10 6 min −1. The pyrolytic bitumen decomposes into oil, gas and carbonaceous residue with an activation energy of 152.16 kJ mole −1 and a frequency of ≈10 14 min −1. The weight loss data were analyzed by the direct Arrhenius, Coats—Redfern and Freeman—Carroll techniques. The kinetic parameters derived from the three methods are discussed in the light of previous work on the thermal decomposition kinetics of oil shale kerogen. Factors influencing kinetic data such as sample holder geometry, heating rate and atmosphere are critically reviewed. The concept of kinetic order is examined in the light of existing theory for solid-state decomposition reactions and it is shown that first-order kinetics are adequate in explaining the overall trends in the thermal behavior of Green River oil shales.