Renewable Energy Focus  Volume 27, Number 00  December 2018 www.renewableenergyfocus.com Study of oxidation behavior of Jatropha oil methyl esters and Karanja oil methyl esters blends with EURO-IV high speed diesel Bhawna Yadav Lamba*, Girdhar Joshi, Devendra Singh Rawat, Sapna Jain and Sanjeev Kumar Department of Chemistry, University of Petroleum & Energy Studies, Dehradun, India Poor oxidation stability of methyl esters is the major problem associated with its worldwide acceptance. As per the standards EN 14214 and prEN16091; and ASTM-D 7545-09 the oxidation stability limit should be 20 h for the blends and 8 h for neat methyl ester. One approach for increasing resistance of fatty acid methyl ester derivatives against autoxidation is to treat them with oxidation inhibitors known as antioxidants. This study examines the effectiveness of five such commercial antioxidants [viz. tert- butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PrG) and pyrogallol (PY)] on the storage stability of Jatropha methyl ester (JOME), Karanja methyl ester (KOME), and their 5%, 10%, 20% and 40% blends with low sulphur EURO-IV High speed Diesel (HSD) using Petrotest PetrOxymeter. The impact of the antioxidants strongly depends on the feed- stock used for biodiesel production. PY was found to be the most effective antioxidant for JOME and its EURO-IV blends; however, PrG has shown maximum effectiveness with KOME and its EURO-IV HSD blends. 500 ppm was found to be the most optimum concentration for both the antioxidants. Introduction In the recent past, increase in energy demand, rise in petroleum prices, and stiff environmental regulations necessitates the search of renewable energy resources [1,2]. Among the renewable energy sources, biodiesel has emerged as a clean burning alternative fuel that can be used in existing engine with little or no modification [3]. Biodiesel is non-flammable, nonexplosive, biodegradable, non-toxic, and can be produced from locally available feedstock [4]. It has comparable fuel characteristics to that of petrodiesel [5–9] and can improve the lubricity and anti-wear properties when blended with petrodiesel [10]. Besides various advantages of biodiesel over conventional diesel, its long-term instability is a major problem. The chief process contributing to the instability of biodiesel and its blends is oxida- tion [11,12]. These oxidation processes are less pronounced in the parent oil due to the presence of natural antioxidants which get partially lost during refining [13] making the oil more prone to oxidation. This leads to increased acid value, density and viscosity and decreased iodine value of biodiesel [14]. In addition to this, oxidation also results in the formation of sediment and gum along with the fuel darkening, which causes filter plugging, injector fouling, deposi- tions in the engine combustion chamber and malfunctions in various components of the fuel system [15]. Therefore, the oxida- tion stability characteristic of biodiesel and its blends is very important property in determining the suitability of biodiesel as a substitute for petro diesel in diesel engines, boilers, electricity generators, and other combustion equipment [16]. The use of commercial additives (i.e. antioxidants) improves the fuel stability by intercepting the reaction of active oxygen and fatty acid, which reduces the oxidation process of biodiesel [17]. In developed countries like United States, the major source of biodiesel is edible oil however, in the growing and overpopulated countries like China and India, the biodiesel production from edible oil resources is not possible. Therefore, non-edible oils (e.g. Jatropha, Pongamia (Karanja), Mahua, Sal, bitter almond oil, date ORIGINAL RESEARCH ARTICLE *Corresponding author Lamba, B.Y. (byadav@ddn.upes.ac.in) 1755-0084/ã 2018 Elsevier Ltd. All rights reserved. https://doi.org/10.1016/j.ref.2018.09.002 59