Cetane Number of Biodiesel from Karaya Oil

Abstract

Biodiesel is a renewable fuel alternative to petroleum Diesel, biodiesel has similar characteristic but with lesser exhaust emission. In this study, transesterification of Karaya oil is examined experimentally using a batch reactor at 100-140°C and 5 bar in subcritical methanol conditions, residence time from 10 to 20 minutes, using a mass ratio 6 methanol-to-vegetable oil. Methanol is used for alcoholysis and sodium hydroxide as a catalyst. Experiments varied the temperature and pressure, observing the effect on the yield and reaction time. In addition, biodiesel from corn oil was created and compared to biodiesel from karaya oil. Kinetic model proposed. The model estimates the concentration of triglycerides, diglycerides, monoglycerides and methyl esters during the reaction. The experiments are carried out at temperatures of 100°C and above. The conversion rate and composition of methyl esters produced from vegetable oils are determined by Gas Chromatography Analysis. It was found that the higher the temperature, the higher reaction rate. Highest yield is 97% at T=140°C achieved in 13 minutes, whereas at T=100°C yield is 68% in the same time interval. Ignition Quality Test (IQT) was utilized for determination of the ignition delay time (IDT) inside a combustion chamber. From the IDT cetane number CN inferred. In case of corn oil biodiesel, the IDT = 3.5 mS, leading to a CN = 58. Whereas karaya oil biodiesel showed IDT = 2.4 mS, leading to a CN = 97. The produced methyl esters were also characterized by measurements of viscosity (υ), density (ρ), flash point (FP) and heat of combustion (HC). The following properties observed: For corn biodiesel, υ = 8.8 mPa-s, ρ = 0.863 g/cm3, FP = 168.8 °C, and HC = 38 MJ/kg. For karaya biodiesel, υ = 10 mPa-s, ρ = 0.877 g/cm3, FP = 158.2 °C, and HC = 39 MJ/kg.