Effect of winterization and plant phenolic-additives on the cold-flow properties and oxidative stability of Karanja biodiesel

Abstract

Poor stability and low-temperature operability are among the major hurdles in the commercialization of biodiesel. The presence of polyunsaturated fatty acid esters renders the fuel susceptible to oxidative attack while the long-chain saturated components limit its utility under low-temperature conditions. In this study, an attempt was made to improve these properties of Karanja biodiesel. Karanja biodiesel synthesized via a two-step alkali-catalyzed process exhibited poor stability and cold-flow properties. Karanja biodiesel was winterized to limit the content of long-chain saturates, and it had a favorable effect on the cloud and pour point of the fuel. Removal of long-chain saturated components led to an enrichment of the fuel in unsaturated fractions, and as a result, the stability of the fuel further deteriorated. For improving, the stability of the fuel T. cordifolia stem extract rich in phenolic constituents was added to winterized biodiesel. The combined treatment of winterization and phenolic-rich extract (1000 ppm) had a pronounced effect on fuel quality as it led to a reduction in the cloud (by 7 °C) and pour point (by 6 °C) and substantially improved the stability of the fuel under accelerated oxidative test conditions. The ASTM D6751, IS 15607, and EN 14214 specifications for the minimum induction period for blendstock biodiesel were satisfied. Thus, coupling the use of winterization and natural antioxidants offers novel opportunities in improving the fuel properties and acceptability of biodiesel in an efficient, economical, and environment-friendly manner.