Physico-chemical properties and thermal degradation studies of commercial oils in nitrogen atmosphere Vikranth Volli, M.K. Purkait ⇑ Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India highlights  Thermal degradation of various commercial oils has been investigated in N 2 atmosphere.  Activation energy of oils calculated in N 2 atmosphere was quite less than that of in air oxidation.  It was observed that free fatty acid content in non-edible oils were more than edible oils.  The order of activation energy was observed as: karanja > soybean > mustard > olive. article info Article history: Received 18 March 2013 Received in revised form 10 October 2013 Accepted 10 October 2013 Available online 23 October 2013 Keywords: Commercial oils Thermogravimetric analysis Iso-conversional method Activation energy Flash point abstract Thermal properties and reaction kinetics of commercial oils play prominent role in design, operation and modeling of systems with various industrial applications including cosmetics, lubrication, fuel and food processing. In the present work, thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTG) techniques were used to study the thermo-chemical behavior of four varieties of oils (mustard, soybean, olive and karanja). The thermal degradation was studied in an inert (N 2 ) atmosphere from ambient temperature to a temperature of 600 °C using a heating rate of 10, 20, 30, 50, 100 °C min 1 . The chemical composition and thermal properties were investigated by measuring FTIR, DSC, CHNS and 1 H NMR. Physical properties such as moisture content, viscosity, ash content, flash, fire, pour and cloud points were also determined. The model-free iso-conversional methods were used to determine kinetic parameters without making any assumptions about the reaction function and reaction order which avoids the risk of obtaining wrong kinetic parameters, especially activation energy, due to pre-assump- tion of inappropriate reaction function. Four degradation models including modified Coats and Redfern, Friedman, Kissinger and Flynn–Wall–Ozawa methods were used to determine the apparent activation energy. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction India is one of the largest producers of commercial edible and non-edible oils with oil seeds are the major sources. About 90% of the vegetable oils produced from these sources are used for edi- ble purpose and the rest are used for varieties of industrial applica- tions. The depletion of petroleum resources lead to an energy crisis and as an alternative, the use of these commercial edible and non-edible oils has been proposed as a raw material in bio-diesel production. The use of these oils poses a great challenge to the scientific community because these are triglycerides (polyunsatu- rated, monounsaturated and saturated fatty acids) and tend to decompose or oxidize under conventional processing conditions. High viscosities of these oils cause durability problems along with poor atomization pattern when used as fuel [1]. Comprehensive knowledge regarding the thermal degradation of oils might result in development and establishment of technologies for various industrial applications. The use of thermo-analytical techniques such as thermogravi- metric analysis (TGA), differential thermogravimetric analysis (DTG) and differential scanning calorimetry (DSC) of oils has gained a lot of importance in recent times. Santos et al. [1] evalu- ated the decomposition kinetics and thermal stability of eight sam- ples of commercial edible oils in air atmosphere at heating rate of 2, 5, 10 and 20 °C min 1 . Integral and approximation methods were used to determine kinetic parameters. The order of stability was determined to be corn > sunflower > soybean > rice > soybean + olive > sunflower + olive > canola > olive. The effects of alpha- tocopherol (vitamin E) on thermal stability and the thermal degradation behavior of sunflower, soybean oil and their blend in air atmosphere at 5, 10 and 20 °C min 1 heating rates were studied by Sanjiv et al. [2]. The sequence of thermal stability was found to be as (sunflower + soybean) > sunflower > soybean. Souza et al. [3] 0016-2361/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fuel.2013.10.021 ⇑ Corresponding author. Tel.: +91 361 2582262; fax: +91 361 2582291. E-mail address: mihir@iitg.ernet.in (M.K. Purkait). Fuel 117 (2014) 1010–1019 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel