Action of natural antioxidants on the oxidative stability of soy biodiesel during storage

Abstract

One of the main problems that the biodiesel industry faces comes from biodiesel's instability when exposed to long storage periods. Its degradation has accelerated by the presence of factors such as oxygen, temperature, metals, humidity, among others. This study adds one more dimension in the field of exploring natural antioxidants to improve the quality of biodiesel, investigating the efficiency of bilberry extracts (BE), oregano (OE) extract, basil extract (BAE), and quercetin (QC) as antioxidants in biodiesel, by non-accelerated methods or analytical methods (water content, acidity value, peroxide value, iodine value, and viscosity) and accelerated methods (Rancimat and PetroOXY) during 180 days of storage. The antioxidant activity evaluated by the capture of the radical ABTS+ [2,2′-azino-bis(3-ethylbenzothiazoline)- 6-sulfonic acid] revealed that among the extracts, the most significant activity was achieved by the oregano extract, followed by the bilberry extract and basil extract. After the storage process, it has observed that the binary samples BBEQC3000 (biodiesel + extract of bilberry + quercetin 3000 ppm), BOEQC3000 (biodiesel + extract of oregano + quercetin 3000 ppm), and BBAEQC3000 (biodiesel + extract of basil + quercetin 3000 ppm) exhibited the least effects of oxidative degradation, both in terms of accelerated and non-accelerated methods. The susceptibility of soy biodiesel to oxidation during storage is well known, and its additivation using natural antioxidants can allow economic gains since natural antioxidants have the advantage of being easy to obtain and relatively low cost, making it a very alternative, viable to delay the oxidative degradation process of biodiesel during storage. The correlation between the Rancimat and PetroOXY techniques during storage revealed that the PetroOXY method could be considered an alternative method to measure the oxidation stability of soybean biodiesel samples and may be used to predict this stability in future standards and standards even though more studies need to be carried out.