Evaluation of the kinetic and thermodynamic parameters in catalytic pyrolysis process of sunflower oil using Al-MCM-41 and zeolite H-ZSM-5

Abstract

The sunflower oil pyrolysis process was evaluated by thermogravimetry coupled to a Fourier transform infrared spectrophotometer (TGA-FTIR), in the presence of microporous (H-ZSM-5) and mesoporous (Al-MCM-41) catalysts in different proportions, to qualitatively evaluate the effect of deoxygenation of pure oil in obtaining renewable hydrocarbons. The catalysts were characterized by techniques and were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and determination of surface acidity. Through these techniques, the catalysts present characteristics consistent with the literature, where they show good structural organization. The reaction kinetics was evaluated using isoconversional methods, e.g., Flynn Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Vyazovkin (VY) at three heating rates (5, 10 and 20 °C min−1) in the conversion range between 20 % and 80 %. The methods present a level of confidence, as they numerically present relatively close Ea values. The apparent activation energies for 50 % conversion of sunflower oil in the absence of catalysts using the FWO, KAS and Vyazovkin methods were 262.56, 255.35 and 234.85 kJ mol−1, respectively; on the other hand, the (50 % wt/wt) H-ZSM-5 and (50 % wt/wt) Al-MCM-41 – OGMH2 mixture showed Ea values corresponding to 152.23, 143.18 and 142.72 kJ mol−1 for the same 50 % conversion, respectively for heating rate of 10 °C min−1. The thermodynamic parameters, viz. enthalpy (ΔH), Gibbs free energy (ΔG) and entropy (ΔS), were calculated with the values of apparent activation energy from the kinetic methods studied.