THERMO-OXIDATIVE DECOMPOSITION ANALYSIS OF PALM WASTES BY ISOCONVERSIONAL KINETICS AND AMMONIA FIBER EXPANSION
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Date
2025-02-20
Authors
Yousef, Duha
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Publisher
An-Najah National University
Abstract
The study examines the thermal decomposition kinetics of raw and bleached palm leaves using thermogravimetric analysis, differential scanning calorimetry, and advanced isoconversional methods like Friedman (FR) and Kissinger-Akahira-Sunose (KAS). From the results obtained in thermogravimetric analysis, distinct degradation profiles in an oxidative atmosphere were observed: raw leaves from 215-565°C and bleached leaves from 200-490°C. Bleaching treatment reduces thermal stability due to lignin removal and hemicellulose, making the material suitable for bioenergy applications.
The kinetic analysis was conducted using the FR and KAS methods in order to determine the effect of the bleaching process. Bleaching decreased the activation energy which therefore increased the decomposition process. In contrast, the FR method gave a wider range of activation energies (300-440 kJ/mol), indicating more complicated reaction mechanisms in the bleached samples, while for the KAS method, the results of activation energy were more stable and lay within a narrow interval (140-190 kJ/mol), reflecting simpler reaction processes. Furthermore, differential scanning calorimetry studies showed that a high heating rate resulted in both a high decomposition temperature and total energy output. The energy release in bleached samples is higher (3411.33 a.u. at 25 °C/min) compared to raw samples (3107.67 a.u.), thus pointing to a significant role of chemical treatment on the decomposition efficiency.
The kinetic modelling showed that the values of the pre-exponential factor (Aα) and the activation entropy (ΔS≠) for raw and bleached palm leaves are statistically different. Thus, at 25% conversion Aα values of raw palm leaves were higher by 1.4×10³⁰ s⁻¹ when compared to the bleached samples of 1.4×10²⁶ s⁻¹. Raw palm leaves also exhibited a higher ΔS≠ (318.5 J/mol⋅K) than bleached samples (241.9 J/mol⋅K), suggesting greater molecular disorder in the raw material. Thermodynamic parameters revealed that raw palm leaves required higher activation enthalpy (ΔH≠ = 351.9 kJ/mol) than bleached samples (ΔH≠ = 299.6 kJ/mol), indicating a more energy-intensive decomposition process.
Fourier transform infrared spectroscopy analysis confirmed structural changes, with the bleaching process reducing lignin and hemicellulose content, thereby simplifying the material’s molecular structure.