Determination of activation energy as a function of conversion for the oxidation of heavy and light crude oils in relation to in situ combustion

Efficient design of in situ combustion depends on accurate kinetic study of crude oil oxidation. We aimed to study the variation of activation energy in both heavy and light crude oils. TG/DTG and DSC performed under atmospheric air from 100 to 800 A degrees C in four different heating rates. Three distinct reaction regions were observed known as low-temperature oxidation, fuel deposition and high-temperature oxidation. Increase in heating rate shifted onset of oxidation reactions to higher temperatures. Three isoconversional kinetic models were also used to analyze the conversion dependence of the activation energy (E (alpha)). Reaction regions were analyzed separately because their reactions schemes are not the same. The estimated E (alpha) values of different models at each degree of conversion were nearly similar. Activation energy of crude oil varied considerably with conversion in some reaction regions. Therefore, average value of activation energy is not always a reliable parameter for in situ combustion models.