Study of the addition of Gabiroba leaves extract in the biodiesel oxidation reaction in the presence of metal ions

Abstract

Biodiesel is considered a renewable energy source, making it possible to reduce the use of fossil fuels and the emissions of gasses derived from sulfur oxides. It is one of the alternatives to diesel due to its similar physicochemical properties. However, this biofuel contains unsaturated methyl esters in its composition, which makes it susceptible to oxidation. Among the factors that alter its chemical stability is its contamination by transition metal ions. This study aimed to evaluate the influence of Cu²⁺, Fe²⁺ and Fe³⁺ ions in the oxidative stability of biodiesel using Gabiroba leaves extract as a natural antioxidant. Metal ions were added to biodiesel in the presence and absence of the extract to evaluate their effect in the induction period and the kinetics and thermodynamic parameters of the oxidation reaction. The Gabiroba leaves extract inhibited the catalytic action of Fe²⁺ and Cu²⁺ cations in biodiesel, but this effect was not observed with Fe³⁺. The thermodynamic parameters of the reactions evaluated by the Eyring equation, based on the activated complex theory, indicated that in all cases the process was non-spontaneous and endothermic: ΔG^‡ > 0, ΔH^‡ > 0, and negative ΔS^‡ values.

Keywords:

• Antioxidant
• biodiesel
• natural extract
• metal ions

Acknowledgments

State University of Londrina (UEL), National Council for Scientific and Technological Development (CNPq), Coordination for the Improvement of Higher Education Personnel (CAPES), Araucaria Foundation to Support Scientific and Technological Development of the State of Paraná and São Paulo Research Foundation (FAPESP - 2020/11463-5).

Disclosure statement

No potential conflict of interest was reported by the authors.