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Thermal characterization of a biodiesel nitration: Bio-additive’s synthesis by calorimetric methods

Diop, Adji, Ben Talouba, Imed, Balland, Laurent, Mouhab, Nordine
Thermochimica acta 2019 v.673 pp. 138-146
additives, biodiesel, calorimetry, canola oil, diesel fuel, gas chromatography-mass spectrometry, heat production, iodine value, nitrates, nitric acid, oleic acid, stearic acid, temperature, thermal stability
The aim of this study was to synthesize a substitute to the 2-Ethyl Hexyl Nitrate (EHN) by nitrating a biodiesel. EHN is commonly used to improve the auto-ignition properties of diesel fuels. The biodiesel was obtained by trans-esterification of canola oil. The nitration reaction was carried out in a reaction calorimetry RC1 with semi-batch mode to study its exothermic behavior. Mixed sulfuric/nitric acid was used as nitrating agent. The impact of the synthesis temperature on the thermal behavior and on the reaction medium composition was investigated. The final product was analyzed by using several analytical techniques such as iodine number, infrared spectrometry, GC–MS and mass spectrometry. This analytical study combined with the results of thermal stability study in DSC, allowed to highlight that chemical transformations play an important role on the thermal reaction behavior and on the Maximum Temperature of the Synthesis Reaction (MTSR). In addition to the mixed acid decomposition, the synthesis at high temperature involves the production of nitrated products: methyl-8-nitro oleate, methyl-10-nitrate stearate, methyl-10-nitrate-9-nitrostearate. Also, the Cooperative Fuel Research (CFR) engine was used to analyze the cetane number of diesel fuel mixed with our additive according to the ASTM D613 standard. The results showed an increase in cetane number of 3.2 points.