Analysis of thermal, oxidative and cold flow properties of methyl and ethyl esters prepared from soybean and mustard oils

Abstract

Oilseed crop with high oil content and promising ecological adaptability are potential sources for competitive biodiesel production. This study investigates the scope of utilizing biodiesel development through the methyl and ethyl ester from soybean and mustard oil as an alternative fuel. Methyl and ethyl esters of oils having different fatty acids compositions such as soybean (SOME and SOEE) and mustard oil (MUME and MUEE) were prepared by transesterification with methanol and ethanol in the presence of an alkali-KOH catalyst. The gas chromatographic (GC) analysis of oil samples revealed that primary fatty acid composition in soybean oil was linoleic acid (C18:2, 51.93%), followed by oleic acid (C18:1, 22.82%), palmitic acid (C16:0, 11.56%), linolenic acid (C18:3, 5.95%) and stearic acid (C18:0, 4.32%). Whereas, the main components in mustard oil were erucic acid (C22:1, 32.81%), oleic acid (C18:1, 24.98%), eicosenoic acid (C20:1, 10.44%), linolenic acid (C18:3, 8.61%) and palmitic acid (C16:0, 2.80%). The physicochemical properties (acid value, iodine value, calorific value, flash point, pour point etc.) of methyl and ethyl ester samples were estimated and found to be within the acceptable range of ASTM D6751 standards specifications. The prepared esters and oil samples were examined for cold flow properties by differential scanning calorimetry (DSC). Results revealed better cold flow properties for MUME (−2.55 °C) and MUEE (−3.10 °C) than SOME (3.21 °C) and SOEE (1.83 °C) due to more unsaturated fatty acid content in MU. Thermal and oxidative stability of samples was determined by thermogravimetric analysis (TG) and differential thermal analysis (DTA). The thermal and oxidative stability ranking of the samples was in the order of oil > methyl esters > ethyl esters.