Non-isothermal thermo-chemical pyrolytic conversion of Modar (Erythrina indica L.) and Mahaneem (Azadirachta indica A.): Kinetics & thermodynamics evaluation

Abstract

Co-feed pyrolysis of lignocellulosic biomass blend presents an intriguing approach to enhance the quantity and quality of pyrolysis products. The approach seeks to leverage the versatility of pyrolysis process and contribute to the advancement of sustainable fuels. In this study, the kinetic triplets and thermodynamics of co-pyrolysis of Modar (Erythrina indica L.) (EI) and Mahaneem (Azadirachta indica A.) (AI) were evaluated at seven varying co-feed ratios $(1:1;1:2;1:3;1:4;2:1;3:1\mathrm{and}4:1)$. For this purpose, thermogravimetric study of the co-feeds were carried out at heating rates of $10,20,30\mathrm{and}40°C/\min$ and this data was further utilized as input for five different iso-conversional methods used to estimate kinetics of the process. Results revealed that the co-feed ratio of 4:1 necessitates the maximum activation energy for its co-pyrolysis, whereas 2:1 ratio demands the minimum. However, considering $R^2$ values, the co-feed ratio of 1:1 emerges out to be the preferable choice for its co-pyrolysis, displaying relatively low activation energy requirements for its co-pyrolysis and consistently high $R^2$ values exceeding 0.99 across all values of the conversion. Average activation energy (E_α) and pre-exponential factor (k_o) values for the pyrolysis of co-feed ratio of 1:1 ranged from $169.643-179.808$ $\mathrm{kJ}/\mathrm{mol}$ and $1.272\times {10}^{13}-5.898\times {10}^{16}{\min }^{-1}$, respectively. Correspondingly, the average values of thermodynamic properties, including enthalpy change (∆H), Gibbs free energy change (∆G), and entropy change (∆S) varied in the range of $164.421-174.819\mathrm{kJ}/\mathrm{mol},173.425-175.288\mathrm{kJ}/\mathrm{mol}\mathrm{and}-0.017-0.002\mathrm{kJ}/\mathrm{mol}K$, respectively. In summary, though the difference between average E_α and ∆H is only ≈ 5 kJ/mol; positive ∆H, positive ∆G and positive ∆S indicate that the co-pyrolysis of EI and AI is possible only at high temperatures.