In the present work, the oxidation stability of diesel, rapeseed (RME), and soybean (SME) fatty acid methyl esters (FAME) and a blend of diesel with 10% (v/v) RME (B10−RME) was studied. Fuel samples were aged in the PetroOxy test device from 383 to 423 K at 7 bar. Experiments were conducted in oxygen excess, and the global kinetic constants were determined. The global kinetic constants for diesel, B10−RME, and RME at 383 K were 7.92 × 10 −6 , 2.78 × 10 −5 , and 8.87 × 10 −5 s −1 , respectively. The oxidation products formed at different stages of the oxidation were monitored by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis−differential thermal analysis (TGA−DTA), and gas chromatography/ mass spectrometry (GC/MS). The impact of the FAME nature and level of blending on the kinetic rate constant and the oxidation products was investigated. Results show that RME oxidation forms C 19 epoxy as the main oxidation product, in addition to a methyl ester FAME derivative and short-chain oxidation products, such as alkane, alkene, aldehydes, ketones, alcohols, and acids with a carbon number up to C 11 . The overall amount of oxidation products increases with a higher degradation time. The DTA profile suggests that higher molecular weight products are formed at an advanced level of oxidation. For all highly oxidized fuels, a similar DTA peak was obtained at a temperature of around 573 K, which may suggest the formation of products having similar molecular weights for both diesel and FAME.

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The study of fuel oxidation stability is an important issue for the development of future fuels. Diesel and kerosene fuel systems have undergone several technological changes to fulfill environmental and economic requirements. These developments have resulted in increasingly severe operating conditions whose suitability for conventional and alternative fuels needs to be addressed. For example, fatty acid methyl esters (FAMEs) introduced as biodiesel are more prone to oxidation and may lead to deposit formation. Although several methods exist to evaluate fuel stability (induction period, peroxides, acids, and insolubles), no technique allows one to monitor the real-time oxidation mechanism and to measure the formation of oxidation intermediates that may lead to deposit formation. In this article, we developed an advanced oxidation procedure (AOP) based on two existing reactors. This procedure allows the simulation of different oxidation conditions and the monitoring of the oxidation progress by the means of macroscopic parameters, such as total acid number (TAN) and advanced analytical methods like gas chromatography coupled to mass spectrometry (GC-MS) and Fourier Transform Infrared -Attenuated Total Reflection (FTIR-ATR). We successfully applied AOP to gain an in-depth understanding of the oxidation kinetics of a model molecule (methyl oleate) and commercial diesel and biodiesel fuels. These developments represent a key strategy for fuel quality monitoring during logistics and on-board utilization.

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