Hi Ahmad! Single heating rate experiments for kinetics studies ARE NOT advised (please see the attached paper).

Article Single heating rate methods are a faulty approach to pyrolys...

I am not sure which kind of experiment you're conducting (TGA, DSC, ...), but normally kinetic studies are conducted under constant pressure, and then the isoconversional methods (or equivalent) are applied to find the kinetic triplets. Can you share a little more about your experimental procedure?

Maurício Azevedo

I performed TPO of non-isothermal coke oxidation at five different partial pressures. I used Coats-Redfern to obtain the activation energy and Pre-Exp. Then I used the differential form of equation dx/dT= A/B exp( -E/RT) * f(x) *po^n. I used minimization method to obtain partial pressure order. Also, I optimized the kinetic parameter further by minimizations as well.

finally, this general comparison between linear and non-linear regression.

I was told by one of my colleagues that the purpose of multiple heating rate is experiment is to get more data which can can give a reliable activation energy and Pre-expontial factor. I was wondering since we perform the experiment single heating rate, but various partial pressure Will this qualify the data for model-free analysis ?

Performing the experiments at different partial pressures will not give you reliable kinetic parameters (triplet: activation energy, pre-exponential factor, reaction order) because kinetics (in this case) is associated to temperature. The different pressures will indeed allow the determination of the function that describes the phonomenon according to a pressure change. For the kinetic triplet, Vyazovkin teaches:

“The Coats-Redfern method is the most popular among the single heating rate methods and rather representative of the problem characteristic of all such methods. This problem resides in the fact that these methods cannot generally pro- duce trustworthy kinetic parameters. In actual practice, a sin- gle heating rate data set can normally be described by several statistically equivalent kinetic triplets [23, 24]. Unfortunately, this fact remains commonly unnoticed because of not performing a proper statistical analysis.”

In this sense, your colleagues are right: if you want reliable kinetic parameters, you should perform additional heating rates.

I hope it helps 😄