Abiding effects of phenolic antioxidants on oxidative behaviour of fatty acid methyl esters derived from waste cooking oil

Abstract

Fatty acid alkyl esters (FAMEs) derived from waste vegetable oils and non-edible oil sources are the most attractive alternative liquid biofuel in the energy field. Substitute methyl esters derived from waste cooking oil (WCO) have a lower induction period (3.12 h) and do not satisfy the Biodiesel EN 14214:2012 Standard (8 h). In this study, concentrations of 100, 250, 500, and 1000 ppm of four different types of phenolic antioxidants—butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butyl hydroquinone (TBHQ), and propyl gallate (PG)—were used to examine oxidative stability and improve fuel quality. PG (250 ppm) showed the most effective result of 18 h to 12.17 h of the induction period of 6 months of storage. Antioxidant effectiveness increased with regard the oxidative stability of waste cooking oil methyl ester in the following order: BHT <TBHQ < BHA< PG. Acid value and kinematic viscosity of WCO biodiesel increase 564.3% and 10.3% respectively, which indicate degradation of fuel quality. But biodiesel with antioxidant, all the parameters changes dynamically. The acid value, kinematic viscosity, and density of all investigated samples increased. All results were within limits of EN 14214:2012 standard specification for the 6 months of storage period.