Monitoring free radicals formation in the biodiesel oxidation reaction via electronic paramagnetic resonance

• Published in: Fuel (Guildford) Vol. 224; pp. 255 - 260
• Main Authors: Mantovani, Ana Carolina Gomes, Chendynski, Letícia Thaís, Salviato, Aroldo, Borsato, Dionísio, Santana, Vinicius Tadeu, Di Mauro, Eduardo
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.07.2018; Elsevier BV
• Subjects: Absorption spectra; Biodiesel fuels; Biofuels; Corn; Degradation; Diesel; Electron paramagnetic resonance; Electron spin; Environmental impact; EPR; Free radicals; Heating; Hydroxyl radicals; Oxidation; Phenyl-N-tert-butylnitrone; Radical reaction; Resonance; Soybeans; Spin trapping; Trapping; Degradation; Oxidation; Radical reaction; Spin trapping; EPR
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2018.03.114

•The radical reactions in biodiesel was studied by EPR.•The spin trapping technique was applied to analyze biodiesel degradation.•EPR monitoring was an important tool in the study of biodiesel radical reactions.•EPR allowed the characterization of the biodiesel degradation steps.•The presence of the hydroxy radical was identified. Biodiesel is an environmentally friendly alternative for petro-diesel. However, its degradation caused by radical oxidative reactions generates free radicals that damage the mechanics of vehicles. Spin trapping is a powerful resource for quantifying the short-lived and unstable free radicals liberated in these reactions. In this work, the formation of free radicals in samples of corn, soybean, and commercial biodiesel was investigated via electron paramagnetic resonance (EPR) using the spin trapping technique. The samples were incubated using the spin trap α-Phenyl-N-tert-butylnitrone (PBN) and analyzed via X-band EPR at room temperature and under heating at 70 °C. The experimental and simulated absorption spectra of the entrapped radicals allowed both identifying the presence of a derivative of the hydroxyl radical and characterizing the degradation stages of biodiesel. This result was discussed and compared with the accelerated heating method. The analysis allowed to establish EPR as a suitable, quick, and inexpensive way of probing the degradation of biodiesel in comparison with standard methods.