Stabilisation of biofuels with hydrophilic, natural antioxidants solubilised by glycerol derivatives

Kerkel, Florian and Brock, Damian and Touraud, Didier and Kunz, Werner (2021) Stabilisation of biofuels with hydrophilic, natural antioxidants solubilised by glycerol derivatives. FUEL, 284: 119055. ISSN 0016-2361, 1873-7153

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Abstract

We present a new concept of implementing natural, hydrophilic antioxidants in lipophilic biofuels without the necessity of classical surfactants. Hydrotropic glycerol derivatives are used to solubilise hydrophilic anti-oxidative agents in biofuels, such as fatty acid methyl esters (FAME). This concept has several advantages, as the antioxidants are obtainable from plants and usually significantly less hazardous than the synthetic antioxidants, such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) or hydroquinone (HQ), currently used in industry. Additionally, the hydrotropes - or better termed "oleotropes" here - used to solubilise the natural antioxidants exhibit favourable fuel properties, while being obtained by simple addition reactions with glycerol - a largely generated by-product during the biodiesel production in industry. Even more, certain natural antioxidants, such as gallic acid, are shown to exhibit significantly better anti-oxidative properties than their synthetic counterparts. In this context, the polar paradox theory is discussed, proposing that potent antioxidants for biofuels should be hydrophilic and exhibit a low solubility in the fuel. Additionally, the efficacy of phenolic antioxidants is correlated with the bond-dissociation enthalpy (BDE) of their phenolic ArO-H bonds and catechol as well as pyrogallol moieties are concluded to represent key structures for effective antioxidants in biofuels. This is shown by investigating the effects of antioxidants on the oxidative stabilities of FAME/rapeseed oil mixtures and a commercial biofuel. Lastly, the presented concept is further extended to use certain glycerol derivatives first to extract natural, hydrophilic antioxidants from a polyphenol-rich plant, and then to effectively stabilise biofuels with the extraction mixture.

Item Type: Article
Uncontrolled Keywords: WATER PARTITION-COEFFICIENTS; OXIDATIVE STABILITY; SYNTHETIC ANTIOXIDANTS; FUEL PROPERTIES; GALLIC ACID; SOYBEAN OIL; BULK OILS; BIODIESEL; Biofuels; Natural antioxidants; Glycerol derivatives; Oleotropes; Plant extraction
Subjects: 500 Science > 540 Chemistry & allied sciences
Divisions: Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry VI - Physical Chemistry (Solution Chemistry) > Prof. Dr. Werner Kunz
Depositing User: Dr. Gernot Deinzer
Date Deposited: 28 Jul 2022 06:49
Last Modified: 28 Jul 2022 06:49
URI: https://pred.uni-regensburg.de/id/eprint/45975

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