Major fuel properties of synthesized biodiesel including cetane index
, flash point, cloud point, pour point, density, kinematic viscosity, total ash and distillation range were determined according to standard ASTM methods.
The manual exclusion of variables provided better results only for the prediction models of flash point, T10, cetane index
, and biodiesel content.
US regulations (40 CFR [section]80.29) specify that fuel Cetane index
(a surrogate for CN based on fuel properties and composition) should be greater than 40 or that aromatics should be less than 35% by volume .
Finally, the Cetane index
was calculated using the ASTM D976  and the results of the distillation curve.
Real-Time Analyzer's Portable Fuel Quality Analyzer (PFQA) determines the following physical and chemical properties for diesel, gasoline and jet fuels in 10 sec: cetane index
, cloud point, density, distillation values (0, 50, 90 and 100%), flash point, freezing point, octane (AKI), pour point and viscosity; as well as aromatics, BTEX, biodiesel, ethanol, FSII, MTBE, naphthenes, olefins, saturates and sulfur.
 AS TM D4737-10 Standard Test Method for Calculated Cetane Index
by Four Variable Equation 2010.
Table 1:Test engine specifications Cylinder bore 87.5 mm Stroke 110 mm Displacement 661 cc Rated power 5 kW at 1500 rpm Compression ratio 17.5: 1 Injection timing 23[degrees] BTDC Table 2: Fuel properties Properties Diesel E5B15 Lower heat value (MJ/kg) 42.5 41.1 Cetane index
48 48.6 Viscosity at 40[degrees]C ([mm.sup.2]/s) 3.18 3.19 Oxygen content (%) -- 3.4
The calculated cetane index
(CCI) is based on Krisnagkura equation :
"The key product characteristics of Oryx GTL diesel that make it such a sought after product are its low density -- which falls outside of the European Automotive Diesel range - and high Cetane Index
. It also has a very low sulphur and aromatic content which provide environmental and operational benefits.
Because the results could not conclude which purification step is the most suitable for improving the quality of biodiesel, it will be necessary to determine other characteristics of biodiesel, like saponification, iodine, peroxide values, cetane index
, water content, fatty acids methyl ester composition, product yield.
This reason being that higher cetane index
due to the addition of biodiesel and the ethanol content due to the improved quality of fuel spray with blended fuels since the boiling point of ethanol is lower than that of neat diesel, higher reaction activity in the fuel rich zone due to the oxygenate of ethanol and the reduction in heat losses due to the lower flame temperature [17, 18, 26-29].
50 Norm ppm S) Cetane number, min 51 Cetane index
, min 46 Density at 15[degrees]C, kg/[m.sup.3] 820-845 Polycycling aromatic hydrocarbons, 11 %(m/m), max.