Effect of Natural Substances as Antioxidants and as Corrosion Inhibitors of Carbon Steel on Soybean Biodiesel

Carlos Alberto Caldas De Souza,Rafael Santos Barbosa,Saionara Luna,Marilena Meira,Lucas Oliveira De Assis

doi:10.1590/1980-5373-mr-2020-0234

Abstract

The use of natural additives in biodiesel has been investigated, however, there is limited information in the literature in relation to their influence on corrosion resistance and oxidative stability. This work aims to investigate the oxidative stability of biodiesel and the corrosion resistance of carbon steel (AISI 1020) in contact with soybean biodiesel solutions (B100) in the presence and absence of natural additives such as: rosmarinic acid, curcumin, gingerol, eugenol, thymol and quercetin. Corrosion and microscopy tests were used to assess corrosion resistance. The Rancimat technique was used to study oxidative stability. The results obtained indicate that curcumin was the best additive in relation to oxidative stability, while rosmarinic acid showed better performance in inhibiting corrosion. The effect of these substances is related to the presence of phenolic compounds or the existence of oxygen in its molecular structure.

Highlights

Biodiesel is obtained the transesterification reaction of vegetable oils or animal lipids with metanol or ethanol, in general, in the presence of basic catalyst, such as KOH and NaOH
The acid value indicates the amount of free fatty acids in the biodiesel
Regarding the effect of adding natural additives on the acid value of biodiesel, it was observed that the addition of curcumin does not significantly affect this parameter[19], and the relationship between this effect and the oxidative stability of the biodiesel has not been established

Summary

Introduction

Biodiesel is obtained the transesterification reaction of vegetable oils or animal lipids with metanol or ethanol, in general, in the presence of basic catalyst, such as KOH and NaOH. Through this reaction, the feedstock is transformed into fatty acid methyl or ethyl esters, which constitutes biodiesel[1]. Soybean biodiesel oxidizes very because it contains in its composition fatty acids such as linolenic, palmitic, oleic, and linoleic acids These acids are unsaturated and are oxidized, forming oil degradation compounds such as free acids, alcohols, and peroxides[3,4]

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