Spectroscopic Characterization of Free Radicals and Determination of the Octane number in some Sudanese Gasoline using Raman Spectroscopy

Abstract

In this study Raman Spectroscopy was used to characterize thefree radicals and to determine the octane number for some types of the Sudanese gasoline. Three groups of gasoline were investigated in this work; the first group contained eight standard gasoline samples, with known octane number, collected from Khartoum Refinery Company (KRC). The Second group contained twelve samples with unknown octane numbers, collected from Khartoum petroleum stations. The third group contained four gasoline samples collected from Cairo Petroleum stations with known octane number and used to confirm the results of this work. The characterization by Raman spectroscopy of the first group was done for two purposes: The first purpose, was to determine the contribution of the bonds like (991 cm-1, 1000 cm-1 ,2873 cm-1,3053cm-1) for Benzene, Toluene, Ethyl- benzene and Xeyline (BTEX), in the octane number. A relationship between the Intensity ratio (I1000/I2873) and the octane numbers was deduced and plotted. It was found that the Intensity ratio increased by increasing the octane number and from this relation a mathematical formula was obtained in order to determine the unknown octane number for the second group. The obtained results confirmed by the comparison with the thirdgroup thatcontained samples with known octane number. The second purpose was the identification of the free radicals inSudanese gasoline that can be used to determine the components of Sudanese gasoline in a simple, uncomplicated and fast way, through the study of the wavenumbers of the radicals bonds. In this work Laser Raman Spectrometer type LIRA 300was used in this study. Light Source Diode Pumping Solid State Laser (DPSSL) with wavelength 532nm and power 40mW was used, as lightsource with an external optical path and two polarizers. In conclusions the results showed a very good agreement withstandard samples so that the octane number for any type of gasoline can be deduced from the relation obtained in this work.In conclusion, Raman spectroscopy can be used efficiently to characterize the Sudanese gasoline by identification of the chemical bonds and the free radicals.