Abstract

Moringa oleifera produces oil which can be extracted and converted to biodiesel. However, the kinetics and thermodynamics of this viable fuel have been seldomly investigated. We examine the kinetics and thermodynamics of the oil extraction for biodiesel production. The biodiesel kinematic viscosity (3.75 ± 0.04 mm²/s), cetane number (67.12), oxidative stability (15.2 ± 0.5), acid value (0.012 mg/KOH), pour point (−9$°\mathrm{C}$) and carbon residue (0.020 $\pm$ 0.001) satisfy the American Society for Testing and Materials (ASTM) limits. Fourier transform infrared spectroscopy distinguishes the biodiesel and the base oil at 1435.77 cm⁻¹ (-CH₃ stretch), 1195.74 cm⁻¹ (O-CH₃) and 1377.67 cm⁻¹ (O-CH₂) because -CH₃ and O-CH₃ stretches are absent in the oil whereas the biodiesel lacks O-CH₂ stretch. The highly negative activation entropy (−214.11 $\pm$ 0.16 J mol⁻¹ K⁻¹) and greater activation enthalpy (30.39 $\pm$ 0.05 kJ/mol) indicate a slower extraction rate due to the higher energy requirement and stiffer transition of the extraction, respectively. The slower extraction rate agrees with the lower mass transfer coefficients (0.0119–0.0210 min⁻¹). The equilibrium constant (K) is positive whilst the Gibbs free energy (ΔG) is negative, indicating a forward and spontaneous process. This investigation of kinetics, thermodynamics and transesterification essentially provides in-depth knowledge on oil extraction and biodiesel production.

摘要

辣木产生的油可以被提取并转化为生物柴油。然而，很少有人研究这种可行燃料的动力学和热力学。我们研究了用于生物柴油生产的油提取的动力学和热力学。生物柴油运动粘度（3.75±0.04 mm ² /s）、十六烷值（67.12）、氧化稳定性（15.2±0.5）、酸值（0.012 mg/KOH）、倾点（-9$°\mathrm{C}$) 和残炭 (0.020 $\pm$ 0.001) 满足美国材料与试验协会 (ASTM) 的限制。傅里叶变换红外光谱在 1435.77 cm ^-1 (-CH ₃拉伸)、1195.74 cm ^-1 (O-CH ₃ )和1377.67 cm ^-1 (O-CH ₂ )处区分生物柴油和基础油，因为-CH ₃和O油中不存在-CH ₃拉伸，而生物柴油缺乏O-CH ₂拉伸。高度负激活熵（−214.11 $\pm$ 0.16 J mol ^-1 K ^-1 ) 和更大的活化焓 (30.39 $\pm$ 0.05 kJ/mol) 分别表示由于较高的能量需求和较硬的萃取过渡，萃取速率较慢。较慢的萃取速率与较低的传质系数 (0.0119–0.0210 min ^-1 ) 一致。平衡常数 (K) 为正，而吉布斯自由能 (ΔG) 为负，表明正向和自发过程。这项对动力学、热力学和酯交换的研究基本上提供了对石油提取和生物柴油生产的深入了解。