Abstract This work aims to evaluatethe thermal decomposition kinetics of coconut fiber in a thermogravimetric analyzer using four heating rates (5-20 °C/min) in nitrogen atmosphere. Three decomposition stages were identified (dehydration, pyrolysis, and carbonization) and the pyrolysis kinetic was performed considering two reaction models (single- and multi-step). In the first model, the apparent activation energy (94.5-210.8 kJ/mol) was determined using five isoconversional methods, and the reaction model representative was the three-dimensional diffusion model, f(α) = (3/2) (1-α)2/3 [1 - (1-α)1/3]-1 obtained using the master plots method. Through the linearization method of the conversion rate equation, the global activation energy found was 129.8 kJ/mol and the pre-exponential factor (log A) was 18.8 1/s. Due to the complexity of the biomass decomposition, the second model, three independent parallel reactions scheme (IPRS), was applied to describe each pseudo-component (hemicellulose, cellulose, and lignin). It was possible to obtain activation energies from 79.1 to 196.3 kJ/mol, pre-exponential factors (log A) from 3.1 to 15.0 1/s, volatilized fractions from 0.3 to 0.5, considering 1 st and 2nd reaction orders. Finally, the modeling of conversions and conversion rates of both approaches was in a good agreement with the experimental data, however, the second model proved accuracy in describing the coconut fiber pyrolysis.

中文翻译：

---

应用单步和多步反应模型的椰子纤维热解分解动力学

摘要 本工作旨在利用热重分析仪在氮气气氛中使用四种加热速率 (5-20 °C/min) 评估椰子纤维的热分解动力学。确定了三个分解阶段（脱水、热解和碳化），并考虑两种反应模型（单步和多步）进行热解动力学。在第一个模型中，表观活化能（94.5-210.8 kJ/mol）采用五种等转化方法测定，反应模型代表为三维扩散模型，f(α) = (3/2) (1- α)2/3 [1 - (1-α)1/3]-1 使用主图法获得。通过转化率方程的线性化方法，发现全局活化能为129.8 kJ/mol，指前因子(log A)为18.8 1/s。由于生物质分解的复杂性，第二个模型，三个独立的平行反应方案（IPRS），被用于描述每个假组分（半纤维素、纤维素和木质素）。考虑到第一和第二反应顺序，可以获得 79.1 到 196.3 kJ/mol 的活化能，3.1 到 15.0 1/s 的指前因子 (log A)，0.3 到 0.5 的挥发分数。最后，两种方法的转化率和转化率建模与实验数据非常吻合，然而，第二个模型证明了描述椰子纤维热解的准确性。1 到 196.3 kJ/mol，指前因子 (log A) 从 3.1 到 15.0 1/s，挥发分数从 0.3 到 0.5，考虑到第一和第二反应顺序。最后，两种方法的转化率和转化率的建模与实验数据非常吻合，但是，第二个模型证明了描述椰子纤维热解的准确性。1 到 196.3 kJ/mol，指前因子 (log A) 从 3.1 到 15.0 1/s，挥发分数从 0.3 到 0.5，考虑到第一和第二反应顺序。最后，两种方法的转化率和转化率建模与实验数据非常吻合，然而，第二个模型证明了描述椰子纤维热解的准确性。