Real-time emission behavior of coconut oil biodiesel during thermal oxidation in air field by thermogravimetry–fourier transform infrared spectroscopy–gas chromatography–mass spectrometry

Real-time monitoring data regarding the emission behavior of medium chain fatty acid esters was still insufficient concerning their oxidative and low-temperature combustion characteristics. Herein, thermogravimetry-Fourier transform infrared spectroscopy-gas chromatography-mass spectrometry (TG-FTIR-GC-MS) was utilized to investigate the emission profile of coconut oil-derived methyl ester biodiesel (MECO) under air flow, with specific emphasis on medium chain fatty acid methyl ester’s oxidative degradation and simulated low-temperature combustion processes. To eliminate nitrogen interference, thermal decomposition behaviors of three high-boiling-point plant oil-based ethyl esters (PEEs), including ethyl ester of coconut oil ( Cocos nucifera L. , EECO), ethyl ester of palm oil ( Elaeis guineensis , EEPO), and ethyl ester of cottonseed oil ( Gossypium barbadense L ., EECSO), were examined under nitrogen flow. The PEEs primarily release fatty acid ethyl esters, demonstrating that nitrogen is not involved in potential PEE pyrolysis. Under air flow, MECO undergoes ester bond cleavage, radical scission, and decarboxylation, yielding special short- to medium-chain alkanes. Reactive molecular dynamics simulations using methyl octanoate as the model compound further elucidated the potential degradation pathway under simulated air conditions. This work establishes a robust framework for understanding potential thermal oxidative degradation of medium chain fatty acid esters, shedding some light on optimizing fuel formulations. • Biodiesels undergo direct emission of FAAEs under a nitrogen atmosphere. • MECO undergo ester bond oxygen-induced cleavage and heat-induced homolytic cleavage. • Mechanistic differences exist between TG-IR-GC-MS and conventional simulated oxidation methods. • MECO exhibits high oxidative stability and can serve as a biodiesel additive.