Role of Antioxidants in Enhancing Oxidation Stability of Biodiesels

Abstract

Chemical composition of biodiesel plays an important role in deciding its oxidation stability. Bisallylic positions in fatty acid ester chain are especially prone to attack by oxygen, leading to the formation of gums, acids, and polymer deposits that cause failing or plugging problems in the engine and filter as consequences. Although oxidation of biodiesel cannot be checked completely, it can be slowed using antioxidants, which prevent the process from continuing by scavenging the free radicals, formed by the attack of oxygen on reactive sites of fatty acid ester chain. Antioxidants having phenolic and amine moiety have been found to be especially effective to enhance the stability. The mode of action and activity of various antioxidants have also been discussed.

Diesel-Injection Equipment Parts Deterioration after Prolonged Use of Biodiesel

“…The most demanding issue with the use of biodiesel is its oxidation stability, which affects performance, emissions, and engine durability ( Figure 1). The more general term biodiesel degradation is referred to the modification of its original composition and properties due to aging, oxidation, and metal corrosion during the storage process [12,16]. The compatibility of seal and hose materials commonly encountered in automotive fuel systems using conventional hydrocarbon fuels has long been established and elastomer manufacturers are able to make recommendations for their use.…”

Efficiency of different additives in the improvement of the oxidation stability of fatty acid methyl esters with different properties

“…The trend of increasing oxidation rate among the most abundant unsaturated fatty acid with 18 C-atoms is as follows: oleic (having 1 unsaturated double bond, shortly marked C18:1) < linoleic (with 2 doubled bonds, marked C18:2) << linolenic (with 3 double bonds, C18:3); [2][3][4] IPs measured at 110 o C for MEs of these fatty acids are: 2.5 h, 1 h and 0.2 h, respectively. 5 A number of excellent reviews on different aspects of biodiesel oxidation have been published. 3,[5][6][7][8][9][10] Apart of fatty acid composition, the presence of minor components such as diacylglycerols, monoacylglycerols, FFAs, phospholipids, moisture and mineral impurities also affects the antioxidant behavior of biodiesel; [10][11][12][13] elevated temperature during storage as well as the exposed surface area between biodiesel and air might increase the oxidative degradation too.…”

“…5 A number of excellent reviews on different aspects of biodiesel oxidation have been published. 3,[5][6][7][8][9][10] Apart of fatty acid composition, the presence of minor components such as diacylglycerols, monoacylglycerols, FFAs, phospholipids, moisture and mineral impurities also affects the antioxidant behavior of biodiesel; [10][11][12][13] elevated temperature during storage as well as the exposed surface area between biodiesel and air might increase the oxidative degradation too. 1 One of the most efficient methods for improving the stability and delaying the oxidative degradation of biodiesel is an addition of antioxidants.…”

Parametric studies on the storage stability and aging effect of biodiesel treated with Eucalyptus oil as a cost‐effective green‐antioxidant additive

“…2 The mechanism of oxidation of biodiesel is mainly dependent upon the fatty acid composition of the parental oil. 3 For instance, the unsaturated and polyunsaturated fatty acids are considerably more reactive to oxidation than saturated fatty acids, 4 where it should be noted that the composition and degree of unsaturation do not change when the vegetable oils are transesterified to biodiesel. The reason for this is that the most reactive sites present in unsaturated fatty acid chains are predominantly liable to the free radical attacks.…”

“…The oxidative stability of biodiesel is affected by many factors during storage, transportation and consumption 2 . The mechanism of oxidation of biodiesel is mainly dependent upon the fatty acid composition of the parental oil 3 . For instance, the unsaturated and polyunsaturated fatty acids are considerably more reactive to oxidation than saturated fatty acids, 4 where it should be noted that the composition and degree of unsaturation do not change when the vegetable oils are transesterified to biodiesel.…”