Department of Chemistry, Egerton University, PO Box 536 -20115, Egerton, Kenya.
School of Chemistry and Physics, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban, 4000, South Africa.
Environ Sci Pollut Res Int. 2018 Sep;25(25):24807-24817. doi: 10.1007/s11356-018-2546-5. Epub 2018 Jun 21.
Pyrolysis of biodiesel at high temperatures may result in the formation of transient and stable free radicals immobilized on particulate emissions. Consequently, free radicals adsorbed on particulates are believed to be precursors for health-related illnesses such as cancer, cardiac arrest, and oxidative stress. This study explores the nature of free radicals and particulate emissions generated when Croton megalocarpus biodiesel is pyrolyzed at 600 °C in an inert environment of flowing nitrogen at a residence time of 0.5 s at 1 atm. The surface morphology of thermal emissions were imaged using a field emission gun scanning electron microscope (FEG SEM) while the radical characteristics were investigated using an electron paramagnetic resonance spectrometer (EPR). A g-value of 2.0024 associated with a narrow ∆Hp-p of 3.65 G was determined. The decay rate constant for the radicals was low (1.86 × 10 s) while the half-life was long ≈ 431 days. The observed EPR characterization of Croton megalocarpus thermal particulates revealed the existence of free radicals typical of those found in coal. The low g-value and low decay rate constant suggests that the free radicals in particulates are possibly carbon-centered. The mechanistic channel for the formation of croton char from model biodiesel component (9-dodecenoic acid, methyl ester) has been proposed in this study.
在高温下进行生物柴油热解可能会导致瞬态和稳定自由基固定在颗粒排放物上。因此，吸附在颗粒上的自由基被认为是与健康相关的疾病（如癌症、心脏骤停和氧化应激）的前体。本研究探索了在惰性环境中以 1 个大气压下 0.5s 的停留时间在流动氮气中以 600°C 热解大戟脂生物柴油时生成的自由基和颗粒排放物的性质。使用场发射枪扫描电子显微镜（FEG SEM）对热排放物的表面形态进行成像，同时使用电子顺磁共振波谱仪（EPR）研究自由基特性。确定了与窄的 ∆Hp-p 为 3.65G 的 2.0024g 值相关的 g 值。自由基的衰减速率常数较低（1.86×10s），半衰期较长≈431 天。观察到大戟脂热颗粒的 EPR 特征表明存在与煤中发现的自由基典型的自由基。低 g 值和低衰减速率常数表明颗粒中的自由基可能是碳中心的。本研究提出了从模型生物柴油成分（9-十二烯酸甲酯）形成克罗顿炭的机理通道。
