Detection of Impurities in Premium Diesel Fuel via Terahertz Frequency Domain Spectroscopy

Abstract

Long-chain hydrocarbons, petroleum and diesel, have long been used as source of energy for locomotives. Unlike it’s short-chain counterpart petroleum, diesel fuel is considered dirtier due to black soot particulates it emits that poses greater health hazard. Here, we attempt to measure the absorbance spectra of premium diesel fuels, neat and adulterated, using terahertz (THz) frequency domain spectroscopy to determine the level of impurities that can further exacerbate its emission. Two broad absorption peaks at 6.42 THz and 7.75 THz as well as narrow peaks at 13.07 THz, 13.88 THz, and in the range of 16-17 THz, characterized the premium diesel. These spectral features are well identifiable in the adulterated samples but their intensities vary depending on the type of impurities. Decrease in the absorbance is observed with water contaminant, increase in isopropanol, while sulfur and methanol contaminants did not influence the absorbance spectra. This technique demonstrates initial but promising results in probing adulteration in petrochemical products.