Determination of palm biodiesel/petroleum diesel blend ratio through spectroscopic method / Alinda Samsuri

Biodiesel, defined as the alkyl esters (usually methyl esters) of vegetable oils, is miscible with conventional petroleum diesel fuel at all blend levels. Blends of biodiesel with conventional petroleum diesel fuel represent a common utilization of biodiesel. The Malaysian Government has initiated the implementation of palm biodiesel since 2007 and the proposed blend is B5. Accordingly, there is interest and need for the development of methods for determining or verifying the blend level of biodiesel in petroleum diesel. To date, the most widely used and acceptable method for determination of biodiesel blend levels is using IR spectroscopy. The present study investigated the determination of blend level of palm biodiesel in petroleum diesel fuel in accordance to European Standard EN 14078:2003. The method was established for the determination of fatty acid methyl esters (FAME) in middle distillates—Infrared spectroscopy method. Principal component analysis of the region 1670 cm-1 to 1820 cm–1 and maximum carbonyl (C=O) absorption peak at 1745 cm-1 ± 5 cm-1 could distinguish blends of petroleum diesel fuel with palm biodiesel. The calibration model was built by following the parameters specified in EN 14078:2003. The peak height was correlated against the FAME concentration in g/L, and the calibration is reported. In the present study, the linearity over the selected range is very good, as evidenced by the R2 value of 0.9999. By using the data from the calibration function, the blend level of palm biodiesel in petroleum diesel was determined easily. Up to 0.2 % error occurs between the measured and an estimated value when used this method to determining the FAME contents in the palm biodiesel-petroleum diesel fuel blend. The adulteration of biodiesel/petroleum diesel blends by palm cooking oil was also successful traced by using thin layer chromatography (TLC) method. Good separation between methyl ester and glycerol was traced using TLC silica gel plate and solvent system chloroform : hexane (1:1 v/v). The amount of acylglycerols adulteration as low as 0.05% can be detected. The detection of adulterant such as acylglycerols in palm biodiesel and petroleum diesel fuel blends via TLC method is a useful and rapid method. It is highly recommended for enforcement exercise during implementation of palm biodiesel blend as there is a high possibility that acylglycerols may be used as an adulterant due to the fact it is cheaper than FAME and it cannot be differentiated from FAME due to the presence of carbonyl functional group.