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