The Effect of Natural and Synthetic Antioxidants on the Oxidative Stability of Biodiesel

Abstract

A significant problem associated with the commercial acceptance of biodiesel is poor oxidative stability. This study investigates the effectiveness of various natural and synthetic antioxidants [a-tocopherol (a-T), butylated hydroxyanisole (BHA), butyl-4-methylphenol (BHT), tert-butylhydroquinone (TBHQ), 2, 5-di-tert-butylhydroquinone (DTBHQ), ionol BF200 (IB), propylgallate (PG), and pyrogallol (PY)] to improve the oxidative stability of soybean oil (SBO-), cottonseed oil (CSO-), poultry fat (PF-), and yellow grease (YG-) based biodiesel at the varying concentrations between 250 and 1,000 ppm. Results indicate that different types of biodiesel have different natural levels of oxidative stability, indicating that natural antioxidants play a significant role in determining oxidative stability. Moreover, PG, PY, TBHQ, BHA, BHT, DTBHQ, and IB can enhance the oxidative stability for these different types of biodiesel. Antioxidant activity increased with increasing concentration. The induction period of SBO-, CSO-, YG-, and distilled SBO-based biodiesel could be improved significantly with PY, PG and TBHQ, while PY, BHA, and BHT show the best results for PF-based biodiesel. This indicates that the effect of each antioxidant on biodiesel differs depending on different feedstock. Moreover, the effect of antioxidants on B20 and B100 was similar; suggesting that improving the oxidative stability of biodiesel can effectively increase that of biodiesel blends. The oxidative stability of untreated SBObased biodiesel decreased with the increasing indoor and outdoor storage time, while the induction period values with adding TBHQ to SBO-based biodiesel remained constant for up to 9 months.

Adsorption in Biodiesel Refining - A Review

“…Oxidative degradation during storage can also compromise fuel quality with respect to effects on kinematic viscosity, acid value, cetane number, total ester content, and formation of hydroperoxides, soluble polymers, and other secondary products (Du Plessis et al, 1985;Bondioli et al, 2002;Thompson et al, 1998). The increased acidity and peroxide values as a result of oxidation reactions can also cause the corrosion of fuel system components, the hardening of rubber components and the erosion of moving parts (Tang et al, 2008). By now the only method for increasing the biodiesel resistance to oxidation is to add synthetic or natural oxidation inhibitors such as tocopherols and hydroquinones.…”

Impact of some natural derivatives on the oxidative stability of soybean oil based biodiesel

“…It was found that the cooperated antioxidants performed better than single one. 13 Tang et al 14 found that pyrogallol (PY), propylgallate (PG) and TBHQ can significantly improve the IP of soybean oil, cotton seed oil, poultry fat and yellow grease based biodiesels, while PY, BHA and BHT showed the best results for poultry fat based biodiesel. Mittelbach and Schober 15 reported that the stability of biodiesels derived from apeseed oil, used frying oil, and tallow was considerably improved with PY, PG, and TBHQ additions, whereas antioxidant BHT was not very effective.…”

Effects of different chemical additives on biodiesel fuel properties and engine performance. A comparison review

“…Oxidative stability of biodiesel was improved by adding natural and synthetic antioxidants at the varying concentrations between 250 and 1000 ppm [31][32][33]. The various natural and synthetic antioxidants [α-tocopherol (α-T), butylated hydroxyanisole (BHA), butyl-4-methylphenol (BHT), tert-butylhydroquinone (TBHQ), 2, 5-di-tert-butyl-hydroquinone (DTBHQ), ionol BF200 (IB), propylgallate (PG), and pyrogallol (PY)] improve the oxidative stability of soybean oil (SBO), cottonseed oil (CSO), poultry fat (PF), and yellow grease (YG) based biodiesel.…”