Shelf-life of Biodiesel by Isothermal Oxidation Induction Period at Variable Temperatures

Biodiesel (fatty acid methyl esters [FAME]) is a renewable biomass-based diesel (BBD) fuel made from plant oils, animal fats and waste greases. Its production continues to increase globally, especially with more countries moving to increase the use of renewable fuels. One of the main disadvantages of biodiesel is its relatively poor oxidative stability. During longer periods of storage at fuel terminals or in vehicle tanks and fuel systems, biodiesel can react with oxygen in ambient air, leading to degradation that can adversely affect its viscosity and ignition quality. The shelf-life of biodiesel is an important property that can determine the conditions such as how long it can be stored at low temperatures. The objective of this work is to develop mathematical equations to estimating the shelf-life of biodiesel at T = 25 °C. This was done by measuring the induction period by Rancimat instrument (IP R ) at different temperatures and extrapolating the results using two types of linear models. Model equations were developed from regression analysis performed on results for canola, palm and soybean oil-FAME (CaME, PME and SME), methyl oleate (MeC18:1) and methyl linoleate (MeC18:2). The best results from confirmation analysis were obtained for Model B type equations. This model type correlated ln(IP R ) with inverse T (T −1 ) data and provided the most realistic estimates of the shelf-life (SL B ) of the five FAME studied in this work.