Synthetic phenolic antioxidants to biodiesel: path toward NOx reduction of an unmodified indirect injection diesel engine
Biodiesel is a green alternative fuel produced from renewable resources. The major disadvantage of biodiesel is the substantial increase in NOx emission. This study examined the effects of antioxidant treated coconut biodiesel on the performance and exhaust emission characteristics of an indirect injection diesel engine. Coconut biodiesel was produced by transesterification using potassium hydroxide as a catalyst. Two low cost synthetic antioxidants, 2(3) tert butyl 4 methoxyphenol (BHA) and 2,6 di tert butyl 4 methylphenol (BHT) were added at 2000 ppm to 20% coconut methyl ester in diesel (CB20) Tests were conducted on a 55 kW 2.5 L four cylinder diesel engine at a constant load varying speed. Results showed that the antioxidants significantly reduced NOx emission with a slight effect on brake thermal efficiency. The addition of BHA and BHT to CB20 reduced the average NOx emission by 7.78% and 3.84% and the average brake specific fuel consumption by 1.77% and 1.46% respectively. The antioxidant addition increased CO, HC, and smoke opacity, but the extent of increase was still below the diesel level. Thus, the addition of antioxidants presents a promising option for NOx reduction.