Kinetic and thermodynamic analysis of Creosote degradation process under isothermal experimental conditions

Abstract

Isothermal degradation process of commercial Creosote was analyzed by the thermogravimetric (TG) technique in a nitrogen atmosphere, at four different operating temperatures (230, 250, 270 and 290°C). The kinetic triplet [E_a , A and f(α)] and the thermodynamic parameters (ΔH ^≠, ΔS ^≠and ΔG ^≠) for investigated Creosote samples were calculated. It was found that two-parameter autocatalytic Šesták-Berggren (SB) kinetic model best describes the process, but in the form of accommodation function with phenomenological character. Applying the multiplicative factor, the true value of activation energy (E ^true _a ) was calculated. The experimental density distribution function of the apparent activation energy values was evaluated from isoconversional kinetic analysis. Based of the characteristic shape of distribution curve, it was concluded that the isothermal degradation of Creosote represents a complex physico-chemical process, given the chemical structure of the studied system. It is assumed that the considered process probably includes primary and secondary (autocatalytic) pyrolysis reactions, together with various decomposition reactions and radicals recombination pathways. The objective of the presented work is the proof of principle of the pyrolysis-based thermo-chemical conversion technologies for the production of value-added chemicals from the complex organic compounds, which even include chemical contaminants (such as PAHs). Also, the present work allows us that by using a unified kinetic approach we can obtain a significant physico-chemical characteristics of the tested system, which can then be used in the procedure for the separation of organics from creosote-treated woods and creosote-contaminated soils. The significance of this research is to identify the global kinetic behavior of some target contaminant compounds for pyrolysis, which are primarily PAHs.

Keywords:

• Thermodynamics
• modeling
• polycyclic aromatic hydrocarbons
• statistics
• transformation

Acknowledgments

The authors would like to thank the Ministry of Science and Environmental Protection of Serbia, for financial support of this research under the Projects 172015 (Bojan Janković) and III43009 (Marija Janković).