Improving oxidation stability and NO<inf>X</inf> reduction of biodiesel blends using aromatic and synthetic antioxidant in a light duty diesel engine

Poor oxidation stability of biodiesel is now a major concern all over the world, especially due to its extensive utilisation in transport and industrialisation. Therefore, biodiesel needs better stability, in order to be sustainably utilised in the long term. The oxygen inhibitor antioxidant can counter the poor oxidation. In this experiment, 20% of Calophyllum inophyllum biodiesel (CIB20) was used as biodiesel feedstock. Three most effective antioxidants N, N'-diphenyl-1, 4-phenylenediamine (DPPD), N-phenyl-1, 4-phenylenediamine (NPPD) and 2-ethylhexyl nitrate (EHN) were used at a 1000 ppm concentration with CIB20. The oxidation stability, exhaust emission and performance of a single cylinder diesel engine were analysed and compared to those of diesel. From the results, it was concluded that there was no significant negative impact on biodiesel physiochemical properties, while the stability of biodiesel (CIB20) with the addition of antioxidants with tested blends increased. Among these three antioxidants, DPPD exhibits a better stability in biodiesel. The results shows that CIB20 produced an average of 5.23% lower brake power (BP), 7.84% less brake thermal efficiency (BTE) and 11.2% higher brake specific fuel consumption (BSFC), compared to pure diesel. However, by mixing the antioxidant with CIB20, the BP and BTE, increased while the BSFC slightly decreased. For exhaust emission, antioxidants reduced NOx by about 5.92%-8.83%, with an increment of hydrocarbon (HC) and carbon-monoxide (CO) for all blends. For this reason, CIB20 blends with aromatic amine antioxidants can be used in diesel engine without any engine modifications