Investigation of oxidation stability of Terminalia belerica biodiesel and its blends with petrodiesel

Terminalia belerica has been identified as a promising feedstock for production of biodiesel in North East India. The major fuel properties of T. belerica biodiesel satisfy both the ASTM and European standard specifications. However, storage behavior as reflected by induction period (IP) does not conform to the standard norms. Two specific issues viz.. (i) comparative assessment of efficacy of antioxidants on freshly prepared terminalia biodiesel and petrodiesel blends and (ii) effect of antioxidants on long term storage behavior of T. belerica biodiesel and petrodiesel blends are considered in this study. The comparative efficacy of six antioxidant additives, viz., Vitamin E (a-tocopherol), butylated hydroxyanisole (BHA), Pyrogallol (PY), Propyl gallate (PG), tert-butylhydroxytoluene (BHT) and tert-butylhydroxyquinone (TBHQ) at varying concentration levels (100 ppm, 500 ppm, 1000 ppm and 1500 ppm) on freshly prepared terminalia biodiesel is investigated. Overall, selected antioxidants could be ranked as PG> PY> TBHQ> BHT> BHA> alpha-tocopherol, on the basis of its efficacy to generate higher IP of freshly prepared samples of T belerica biodiesel (B100). Further, only PY (6.23 h) and PG (6.45 h) additives could improve the IP of pure biodiesel (B100) above the minimum limit of 6 h (EN14214) with minimum dose of 100 ppm. Three antioxidants (PG. TBHQ and BHT) are tested for their activity on stored samples and found that safe storage period could be elongated by adding antioxidants. However, achievable safe storage period differs according to the type and concentration of antioxidants. Up to 12 weeks of safe storage period of T belerica biodiesel could be achieved by adding PG at 1000 ppm concentration. (C) 2012 Elsevier B.V. All rights reserved.